How to drop a Unique Constraint set on a single column - sql

I have created a table below,
"CREATE TABLE UNIQ(NUM INT UNIQUE, NAMES VARCHAR(10))"
Now i want to drop/disable the UNIQUE constraint set on NUM column.
How to do this with Query..?
I googled and got to know that, if i am giving constraint name while creating table, then using that name i can easily drop the contraint.
EX:
CREATE TABLE UNIQ(NUM INT CONSTRAINT CONTR_NAME UNIQUE, NAMES VARCHAR(10))
For dropping constraint.,
ALTER TABLE UNIQ DROP CONSTRAINT CONTR_NAME
Thanks in advance.. :)
Thanks
Mahesh


ALTER TABLE UNIQ
DROP CONSTRAINT [name of constraint]
The below query should help you find the name of the constraint
SELECT
o.name AS ConstraintName,
c.name AS ColumnName
FROM sys.objects o
JOIN sys.objects p
ON o.parent_object_id = p.object_id
JOIN sys.columns c
ON c.object_id = p.object_id
WHERE o.type_desc LIKE '%CONSTRAINT'
AND p.Name = 'UNIQ'


Try this:
DECLARE #ConstraintName VARCHAR(256)
SET #ConstraintName = (
SELECT obj.name
FROM sys.columns col
LEFT OUTER JOIN sys.objects obj
ON obj.object_id = col.default_object_id
AND obj.type = 'UQ'
WHERE col.object_id = OBJECT_ID('TableName')
AND obj.name IS NOT NULL
AND col.name = 'ColunmName'
)
IF(#ConstraintName IS NOT NULL)
BEGIN
EXEC ('ALTER TABLE [TableName] DROP CONSTRAINT ['+#ConstraintName+']')
END

Related

Unable to get table column constraint in T-SQL

I have to create a T-SQL script to update the column datatype but the default constraints do not allow it so I have to first remove the constraints and then alter the column.
I have tried to pass the table column constraint but it does not work.
SELECT
obj_table.NAME AS 'table',
columns.NAME AS 'column',
obj_Constraint.NAME AS 'constraint',
obj_Constraint.type AS 'type'
FROM
sys.objects obj_table
JOIN
sys.objects obj_Constraint ON obj_table.object_id = obj_Constraint.parent_object_id
JOIN
sys.sysconstraints constraints ON constraints.constid = obj_Constraint.object_id
JOIN
sys.columns columns ON columns.object_id = obj_table.object_id
AND columns.column_id = constraints.colid
AND columns.NAME = 'trans_reject_id'
WHERE
obj_table.NAME = 'abc_transaction_table'
ORDER BY
'table'
ALTER TABLE abc_transaction_table
DROP CONSTRAINT DF__abc_trans__ach_r__575DE8F7
Any help would be appreciated.

To Alter column constraint you need to write your query in this way:
DECLARE #CONSTRAINT AS VARCHAR(255)
SET #CONSTRAINT = (SELECT obj_Constraint.NAME AS 'constraint'
FROM sys.objects obj_table
JOIN sys.objects obj_Constraint
ON obj_table.object_id = obj_Constraint.parent_object_id
JOIN sys.sysconstraints constraints
ON constraints.constid = obj_Constraint.object_id
JOIN sys.columns columns
ON columns.object_id = obj_table.object_id
AND columns.column_id = constraints.colid
WHERE obj_table.NAME='abc_transaction_table'
AND columns.Name = 'trans_reject_id'
)
DECLARE #REMOVE_CONSTARINT VARCHAR(255)
SET #REMOVE_CONSTARINT = 'ALTER TABLE abc_transaction_table DROP CONSTRAINT' + #CONSTRAINT
EXEC(#REMOVE_CONSTARINT)

Try something like this
SELECT dc.name constraint_name,
schema_name(dc.schema_id) schema_name,
object_name(dc.parent_object_id) table_name,
c.name column_name
FROM sys.default_constraints dc
join sys.columns c
on dc.parent_column_id = c.column_id
and dc.parent_object_id = c.object_id

Drop constraint names received from different query

I'm trying to drop a few constraints which have been automatically generated when I add the default value somewhere.
I use the following script to return me the names of the constraints:
SELECT default_constraints.name FROM sys.all_columns
INNER JOIN sys.tables ON all_columns.object_id = tables.object_id
INNER JOIN sys.schemas ON tables.schema_id = schemas.schema_id
INNER JOIN sys.default_constraints ON all_columns.default_object_id = default_constraints.object_id
WHERE tables.name = 'TrainingType'
AND default_constraints.name like 'DF__TrainingT__Soft__%'
OR default_constraints.name like 'DF__TrainingT__EndUs__%'
OR default_constraints.name like 'DF__TrainingC__Compu__%'
This returns me the following:
| name
---------------------------------
1 | DF__TrainingC__Compu__2058C9F1
2 | DF__TrainingT__EndUs__1559B68C
3 | DF__TrainingT__Softw__05CD5A39
Now I'm trying to drop the constraints with these values, but it doesn't allow me to do DROP CONSTRAINT ( ... )
ALTER TABLE TrainingType
DROP CONSTRAINT (
SELECT default_constraints.name FROM sys.all_columns
INNER JOIN sys.tables ON all_columns.object_id = tables.object_id
INNER JOIN sys.schemas ON tables.schema_id = schemas.schema_id
INNER JOIN sys.default_constraints ON all_columns.default_object_id = default_constraints.object_id
WHERE tables.name = 'TrainingType'
AND default_constraints.name like 'DF__TrainingT__Soft__%'
OR default_constraints.name like 'DF__TrainingT__EndUs__%'
OR default_constraints.name like 'DF__TrainingC__Compu__%'
)
So how can I drop the constraints correctly?

Dynamic Sql using the select ... for xml path ('') method of string concatenation to concatenate the commands into one variable to execute with sp_executesql:
declare #sql nvarchar(max);
select #sql = (
select
'alter table '+quotename(schema_name(dc.schema_id))
+'.'+quotename(object_name(dc.parent_object_id))
+' drop constraint '+quotename(name)+';'+char(10)
from sys.default_constraints as dc
where parent_object_id = object_id(N'TrainingType')
and dc.name like 'DF__TrainingT__Soft__%'
or dc.name like 'DF__TrainingT__EndUs__%'
or dc.name like 'DF__TrainingC__Compu__%'
for xml path (''), type).value('.','nvarchar(max)')
set #sql = 'use '+quotename(db_name())+';'+char(10)+#sql;
select #sql
exec sp_executesql #sql;
This is a good primer on dynamic sql:
The curse and blessings of dynamic SQL - Erland Sommarskog
rextester demo: http://rextester.com/HSV25230
Generated code from the demo:
use [rextester];
alter table [dbo].[Pilots] drop constraint [DF__Pilots__df__173EF6DF];
alter table [dbo].[Pilots] drop constraint [DF__Pilots__other_df__18331B18];

Maybe it'll work once you add the ID as column and name as a second column.
This should be the proper syntax:
ALTER TABLE "table_name"
DROP [CONSTRAINT|INDEX] "CONSTRAINT_NAME";

You can't inject dynamic qualifiers into a drop clause like that. They have to be issued one at a time. A similar method would be to generate a script to run as individual sql commands.
SELECT
'ALTER TABLE TrainingType DROP CONSTRAINT ( '
+ default_constraints.name +')'
+ CHAR(10)+CHAR(13)+ GO '
FROM sys.all_columns
INNER JOIN sys.tables ON all_columns.object_id = tables.object_id
....
You now have one statement per drop command that you can apply against your database.

How to drop foreign keys of a particular column

I have created a foreign key without specifying the name so sql server has created it with auto generated name. Now I want to drop the column which has this foreign key. The problem is that i don't know the name of this foreign key. Is there any way to drop all the foreign keys for particular column in particular table?
So far I've found this script which drops all default constraints for column
DECLARE #tableName VARCHAR(MAX)
DECLARE #ConstraintName nvarchar(200)
DECLARE #columnName VARCHAR(MAX)
SET #tableName = 'tablename'
SET #columnName = 'columnname'
SELECT #ConstraintName = Name
FROM SYS.DEFAULT_CONSTRAINTS
WHERE PARENT_OBJECT_ID = OBJECT_ID(#tableName)
AND PARENT_COLUMN_ID = (
SELECT column_id FROM sys.columns
WHERE NAME = #columnName AND object_id = OBJECT_ID(#tableName))
IF #ConstraintName IS NOT NULL
BEGIN
EXEC('ALTER TABLE '+#tableName+' DROP CONSTRAINT ' + #ConstraintName)
END
ALTER TABLE [tablename] DROP COLUMN columnname
GO
But it doesn't help with foreign key constraints.

If you want to get more information about FK and specifically about a particular scheme and table than you can use.
SELECT
t.Name as TableName,
c.name as ColumnName,
fk.name as FK_NAME
FROM sys.foreign_keys as fk
inner join sys.tables as t on fk.parent_object_id = t.object_id
inner join sys.columns as c on c.object_id = t.object_id
inner join sys.schemas as sc on t.schema_id = sc.schema_id
WHERE sc.name = 'Schema' and t.name = 'Table' and c.name = 'Column'
If you are interested only about certain column then u can use Ross Presser answer.
Also if you want to drop all fk constraint you can execute this:
Declare #sql nvarchar(4000)
SET #sql = N'';
SELECT #sql = #sql + '
ALTER TABLE [' + sc.NAME + '].[' + OBJECT_NAME(fk.parent_object_id) + ']' + ' DROP CONSTRAINT ' + '[' + fk.NAME + ']
'
FROM sys.foreign_keys as fk
inner join sys.tables as t on fk.parent_object_id = t.object_id
inner join sys.columns as c on c.object_id = t.object_id
inner join sys.schemas as sc on t.schema_id = sc.schema_id
WHERE sc.name = 'schemaName' and c.name = 'columnName' -- you can include and fk name
ORDER BY fk.NAME
PRINT #sql;
--EXEC sys.sp_executesql #sql;

You can get all the constraint list along with the names assigned to particular tables with the help of the below query:
SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS
WHERE TABLE_NAME='YourTableName';
Once you find the constraint you want to delete you can do it with the help of below query:
ALTER TABLE Orders
DROP CONSTRAINT constraint_name;

You can find all constraints throughout the database that use the column:
SELECT * FROM INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE CCU
WHERE CCU.COLUMN_NAME='someColumn'
The output gives the constraint name and the table it is attached to.

Here's an example to find foreign keys using the system views (which aren't amazingly well documented):
select fk.name as ForeignKeyName
, t_parent.name as ParentTableName
, c_parent.name as ParentColumnName
, t_child.name as ReferencedTableName
, c_child.name as ReferencedColumnName
from sys.foreign_keys fk
inner join sys.foreign_key_columns fkc on fkc.constraint_object_id = fk.object_id
inner join sys.tables t_parent on t_parent.object_id = fk.parent_object_id
inner join sys.columns c_parent on fkc.parent_column_id = c_parent.column_id
and c_parent.object_id = t_parent.object_id
inner join sys.tables t_child on t_child.object_id = fk.referenced_object_id
inner join sys.columns c_child on c_child.object_id = t_child.object_id
and fkc.referenced_column_id = c_child.column_id
order by t_parent.name, c_parent.name

How do I drop a foreign key constraint only if it exists in sql server?

I can drop a table if it exists using the following code but do not know how to do the same with a constraint:
IF EXISTS(SELECT 1 FROM sys.objects WHERE OBJECT_ID = OBJECT_ID(N'TableName') AND type = (N'U')) DROP TABLE TableName
go
I also add the constraint using this code:
ALTER TABLE [dbo].[TableName]
WITH CHECK ADD CONSTRAINT [FK_TableName_TableName2] FOREIGN KEY([FK_Name])
REFERENCES [dbo].[TableName2] ([ID])
go

This is a lot simpler than the current proposed solution:
IF (OBJECT_ID('dbo.FK_ConstraintName', 'F') IS NOT NULL)
BEGIN
ALTER TABLE dbo.TableName DROP CONSTRAINT FK_ConstraintName
END
If you need to drop another type of constraint, these are the applicable codes to pass into the OBJECT_ID() function in the second parameter position:
C = CHECK constraint
D = DEFAULT (constraint or stand-alone)
F = FOREIGN KEY constraint
PK = PRIMARY KEY constraint
UQ = UNIQUE constraint
You can also use OBJECT_ID without the second parameter.
Full List of types here:
Object type:
AF = Aggregate function (CLR)
C = CHECK constraint
D = DEFAULT (constraint or stand-alone)
F = FOREIGN KEY constraint
FN = SQL scalar function
FS = Assembly (CLR) scalar-function
FT = Assembly (CLR) table-valued function
IF = SQL inline table-valued function
IT = Internal table
P = SQL Stored Procedure
PC = Assembly (CLR) stored-procedure
PG = Plan guide
PK = PRIMARY KEY constraint
R = Rule (old-style, stand-alone)
RF = Replication-filter-procedure
S = System base table
SN = Synonym
SO = Sequence object
Applies to: SQL Server 2012 through SQL Server 2014.
SQ = Service queue
TA = Assembly (CLR) DML trigger
TF = SQL table-valued-function
TR = SQL DML trigger
TT = Table type
U = Table (user-defined)
UQ = UNIQUE constraint
V = View
X = Extended stored procedure

The more simple solution is provided in Eric Isaacs's answer. However, it will find constraints on any table. If you want to target a foreign key constraint on a specific table, use this:
IF EXISTS (SELECT *
FROM sys.foreign_keys
WHERE object_id = OBJECT_ID(N'FK_TableName_TableName2')
AND parent_object_id = OBJECT_ID(N'dbo.TableName')
)
ALTER TABLE [dbo].[TableName] DROP CONSTRAINT [FK_TableName_TableName2]

In SQL Server 2016 you can use DROP IF EXISTS:
CREATE TABLE t(id int primary key,
parentid int
constraint tpartnt foreign key references t(id))
GO
ALTER TABLE t
DROP CONSTRAINT IF EXISTS tpartnt
GO
DROP TABLE IF EXISTS t
See https://web.archive.org/web/20151105064708/http://blogs.msdn.com/b/sqlserverstorageengine/archive/2015/11/03/drop-if-exists-new-thing-in-sql-server-2016.aspx

IF (OBJECT_ID('DF_Constraint') IS NOT NULL)
BEGIN
ALTER TABLE [dbo].[tableName]
DROP CONSTRAINT DF_Constraint
END

James's answer works just fine if you know the name of the actual constraint. The tricky thing is that in legacy and other real world scenarios you may not know what the constraint is called.
If this is the case you risk creating duplicate constraints, to avoid you can use:
create function fnGetForeignKeyName
(
#ParentTableName nvarchar(255),
#ParentColumnName nvarchar(255),
#ReferencedTableName nvarchar(255),
#ReferencedColumnName nvarchar(255)
)
returns nvarchar(255)
as
begin
declare #name nvarchar(255)
select #name = fk.name from sys.foreign_key_columns fc
join sys.columns pc on pc.column_id = parent_column_id and parent_object_id = pc.object_id
join sys.columns rc on rc.column_id = referenced_column_id and referenced_object_id = rc.object_id
join sys.objects po on po.object_id = pc.object_id
join sys.objects ro on ro.object_id = rc.object_id
join sys.foreign_keys fk on fk.object_id = fc.constraint_object_id
where
po.object_id = object_id(#ParentTableName) and
ro.object_id = object_id(#ReferencedTableName) and
pc.name = #ParentColumnName and
rc.name = #ReferencedColumnName
return #name
end
go
declare #name nvarchar(255)
declare #sql nvarchar(4000)
-- hunt for the constraint name on 'Badges.BadgeReasonTypeId' table refs the 'BadgeReasonTypes.Id'
select #name = dbo.fnGetForeignKeyName('dbo.Badges', 'BadgeReasonTypeId', 'dbo.BadgeReasonTypes', 'Id')
-- if we find it, the name will not be null
if #name is not null
begin
set #sql = 'alter table Badges drop constraint ' + replace(#name,']', ']]')
exec (#sql)
end

ALTER TABLE [dbo].[TableName]
DROP CONSTRAINT FK_TableName_TableName2

Declare #FKeyRemoveQuery NVarchar(max)
IF EXISTS(SELECT 1 FROM sys.foreign_keys WHERE parent_object_id = OBJECT_ID(N'dbo.TableName'))
BEGIN
SELECT #FKeyRemoveQuery='ALTER TABLE dbo.TableName DROP CONSTRAINT [' + LTRIM(RTRIM([name])) + ']'
FROM sys.foreign_keys
WHERE parent_object_id = OBJECT_ID(N'dbo.TableName')
EXECUTE Sp_executesql #FKeyRemoveQuery
END

The accepted answer on this question doesn't seem to work for me. I achieved the same thing with a slightly different method:
IF (select object_id from sys.foreign_keys where [name] = 'FK_TableName_TableName2') IS NOT NULL
BEGIN
ALTER TABLE dbo.TableName DROP CONSTRAINT FK_TableName_TableName2
END

I think this will helpful to you...
DECLARE #ConstraintName nvarchar(200)
SELECT
#ConstraintName = KCU.CONSTRAINT_NAME
FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS AS RC
INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS KCU
ON KCU.CONSTRAINT_CATALOG = RC.CONSTRAINT_CATALOG
AND KCU.CONSTRAINT_SCHEMA = RC.CONSTRAINT_SCHEMA
AND KCU.CONSTRAINT_NAME = RC.CONSTRAINT_NAME
WHERE
KCU.TABLE_NAME = 'TABLE_NAME' AND
KCU.COLUMN_NAME = 'TABLE_COLUMN_NAME'
IF #ConstraintName IS NOT NULL EXEC('alter table TABLE_NAME drop CONSTRAINT ' + #ConstraintName)
It will delete foreign Key Constraint based on specific table and column.

You can use those queries to find all FKs for your table.
Declare #SchemaName VarChar(200) = 'Schema Name'
Declare #TableName VarChar(200) = 'Table name'
-- Find FK in This table.
SELECT
'IF EXISTS (SELECT * FROM sys.foreign_keys WHERE object_id = OBJECT_ID(N''' +
'[' + OBJECT_SCHEMA_NAME(FK.parent_object_id) + '].[' + FK.name + ']'
+ ''') AND parent_object_id = OBJECT_ID(N''' +
'[' + OBJECT_SCHEMA_NAME(FK.parent_object_id) + '].['
+ OBJECT_NAME(FK.parent_object_id) + ']' + ''')) ' +
'ALTER TABLE ' + OBJECT_SCHEMA_NAME(FK.parent_object_id) +
'.[' + OBJECT_NAME(FK.parent_object_id) +
'] DROP CONSTRAINT ' + FK.name
, S.name , O.name, OBJECT_NAME(FK.parent_object_id)
FROM sys.foreign_keys AS FK
INNER JOIN Sys.objects As O
ON (O.object_id = FK.parent_object_id )
INNER JOIN SYS.schemas AS S
ON (O.schema_id = S.schema_id)
WHERE
O.name = #TableName
And S.name = #SchemaName
-- Find the FKs in the tables in which this table is used
SELECT
' IF EXISTS (SELECT * FROM sys.foreign_keys WHERE object_id = OBJECT_ID(N''' +
'[' + OBJECT_SCHEMA_NAME(FK.parent_object_id) + '].[' + FK.name + ']'
+ ''') AND parent_object_id = OBJECT_ID(N''' +
'[' + OBJECT_SCHEMA_NAME(FK.parent_object_id) + '].['
+ OBJECT_NAME(FK.parent_object_id) + ']' + ''')) ' +
' ALTER TABLE ' + OBJECT_SCHEMA_NAME(FK.parent_object_id) +
'.[' + OBJECT_NAME(FK.parent_object_id) +
'] DROP CONSTRAINT ' + FK.name
, S.name , O.name, OBJECT_NAME(FK.parent_object_id)
FROM sys.foreign_keys AS FK
INNER JOIN Sys.objects As O
ON (O.object_id = FK.referenced_object_id )
INNER JOIN SYS.schemas AS S
ON (O.schema_id = S.schema_id)
WHERE
O.name = #TableName
And S.name = #SchemaName

Ok, I know I'm late to the party, but here is the syntax I think is best. Add a schema name if needed to the OBJECT_ID clause.
IF OBJECTPROPERTY(OBJECT_ID(N'My_FK_name'),'IsConstraint') =1
ALTER TABLE dbo.TableName DROP CONSTRAINT My_FK_name

All table constraints will be stored in INFORMATION_SCHEMA.TABLE_CONSTRAINTS
IF EXISTS(SELECT * FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS AS C WHERE C.CONSTRAINT_NAME = '<CONSTRAINT NAME>' AND C.TABLE_NAME = '<TABLE NAME>')
BEGIN
ALTER TABLE <TABLE NAME>
DROP CONSTRAINT <CONSTRAINT NAME>
END
GO

This worked smoothly for Azure Sql server:
IF (OBJECT_ID('dbo.FK_company_id', 'F') IS NOT NULL)
BEGIN
ALTER TABLE dbo.table_company DROP CONSTRAINT FK_company_id
END

How can I list all foreign keys referencing a given table in SQL Server?

I need to remove a highly referenced table in a SQL Server database. How can I get a list of all the foreign key constraints I will need to remove in order to drop the table?
(SQL answers preferable over clicking about in the GUI of the management studio.)

Not sure why no one suggested but I use sp_fkeys to query foreign keys for a given table:
EXEC sp_fkeys 'TableName'
You can also specify the schema:
EXEC sp_fkeys #pktable_name = 'TableName', #pktable_owner = 'dbo'
Without specifying the schema, the docs state the following:
If pktable_owner is not specified, the default table visibility rules
of the underlying DBMS apply.
In SQL Server, if the current user owns a table with the specified
name, that table's columns are returned. If pktable_owner is not
specified and the current user does not own a table with the specified
pktable_name, the procedure looks for a table with the specified
pktable_name owned by the database owner. If one exists, that table's
columns are returned.

This gives you:
The FK itself itself
Schema that the FK belongs to
The "referencing table" or the table that has the FK
The "referencing column" or the column inside referencing table that points to the FK
The "referenced table" or the table that has the key column that your FK is pointing to
The "referenced column" or the column that is the key that your FK is pointing to
Code below:
SELECT obj.name AS FK_NAME,
sch.name AS [schema_name],
tab1.name AS [table],
col1.name AS [column],
tab2.name AS [referenced_table],
col2.name AS [referenced_column]
FROM sys.foreign_key_columns fkc
INNER JOIN sys.objects obj
ON obj.object_id = fkc.constraint_object_id
INNER JOIN sys.tables tab1
ON tab1.object_id = fkc.parent_object_id
INNER JOIN sys.schemas sch
ON tab1.schema_id = sch.schema_id
INNER JOIN sys.columns col1
ON col1.column_id = parent_column_id AND col1.object_id = tab1.object_id
INNER JOIN sys.tables tab2
ON tab2.object_id = fkc.referenced_object_id
INNER JOIN sys.columns col2
ON col2.column_id = referenced_column_id AND col2.object_id = tab2.object_id

I'd use the Database Diagramming feature in SQL Server Management Studio, but since you ruled that out - this worked for me in SQL Server 2008 (don't have 2005).
To get list of referring table and column names...
select
t.name as TableWithForeignKey,
fk.constraint_column_id as FK_PartNo, c.
name as ForeignKeyColumn
from
sys.foreign_key_columns as fk
inner join
sys.tables as t on fk.parent_object_id = t.object_id
inner join
sys.columns as c on fk.parent_object_id = c.object_id and fk.parent_column_id = c.column_id
where
fk.referenced_object_id = (select object_id
from sys.tables
where name = 'TableOthersForeignKeyInto')
order by
TableWithForeignKey, FK_PartNo
To get names of foreign key constraints
select distinct name from sys.objects where object_id in
( select fk.constraint_object_id from sys.foreign_key_columns as fk
where fk.referenced_object_id =
(select object_id from sys.tables where name = 'TableOthersForeignKeyInto')
)

Try this :
sp_help 'TableName'

You should also mind the references to other objects.
If the table was highly referenced by other tables than it’s probably also highly referenced by other objects such as views, stored procedures, functions and more.
I’d really recommend GUI tool such as ‘view dependencies’ dialog in SSMS or free tool like ApexSQL Search for this because searching for dependencies in other objects can be error prone if you want to do it only with SQL.
If SQL is the only option you could try doing it like this.
select O.name as [Object_Name], C.text as [Object_Definition]
from sys.syscomments C
inner join sys.all_objects O ON C.id = O.object_id
where C.text like '%table_name%'

The original question asked to get a list of all foreign keys into a highly referenced table so that the table can be removed.
This little query returns all the 'drop foreign key' commands needed to drop all foreign keys into a particular table:
SELECT
'ALTER TABLE ['+sch.name+'].['+referencingTable.Name+'] DROP CONSTRAINT ['+foreignKey.name+']' '[DropCommand]'
FROM sys.foreign_key_columns fk
JOIN sys.tables referencingTable ON fk.parent_object_id = referencingTable.object_id
JOIN sys.schemas sch ON referencingTable.schema_id = sch.schema_id
JOIN sys.objects foreignKey ON foreignKey.object_id = fk.constraint_object_id
JOIN sys.tables referencedTable ON fk.referenced_object_id = referencedTable.object_id
WHERE referencedTable.name = 'MyTableName'
Example output:
[DropCommand]
ALTER TABLE [dbo].[OtherTable1] DROP CONSTRAINT [FK_OtherTable1_MyTable]
ALTER TABLE [dbo].[OtherTable2] DROP CONSTRAINT [FK_OtherTable2_MyTable]
Omit the WHERE-clause to get the drop commands for all foreign keys in the current database.

Here's the SQL code I would use.
SELECT
f.name AS 'Name of Foreign Key',
OBJECT_NAME(f.parent_object_id) AS 'Table name',
COL_NAME(fc.parent_object_id,fc.parent_column_id) AS 'Fieldname',
OBJECT_NAME(t.object_id) AS 'References Table name',
COL_NAME(t.object_id,fc.referenced_column_id) AS 'References fieldname',
'ALTER TABLE [' + OBJECT_NAME(f.parent_object_id) + '] DROP CONSTRAINT [' + f.name + ']' AS 'Delete foreign key',
'ALTER TABLE [' + OBJECT_NAME(f.parent_object_id) + '] WITH NOCHECK ADD CONSTRAINT [' +
f.name + '] FOREIGN KEY([' + COL_NAME(fc.parent_object_id,fc.parent_column_id) + ']) REFERENCES ' +
'[' + OBJECT_NAME(t.object_id) + '] ([' +
COL_NAME(t.object_id,fc.referenced_column_id) + '])' AS 'Create foreign key'
-- , delete_referential_action_desc AS 'UsesCascadeDelete'
FROM sys.foreign_keys AS f,
sys.foreign_key_columns AS fc,
sys.tables t
WHERE f.OBJECT_ID = fc.constraint_object_id
AND t.OBJECT_ID = fc.referenced_object_id
AND OBJECT_NAME(t.object_id) = 'Employees' -- Just show the FKs which reference a particular table
ORDER BY 2
It's not particularly clear SQL, so let's look at an example.
So, supposing I wanted to drop the Employees table in Microsoft's beloved Northwind database, but SQL Server told me that one or more Foreign Keys were preventing me from doing this.
The SQL command above would return these results...
It shows me that there are 3 Foreign Keys which reference the Employees table. In other words, I wouldn't be allowed to delete (drop) this table until these three Foreign Keys are first deleted.
In the results, the first row is how the following Foreign Key constraint would be shown in the results.
ALTER TABLE [dbo].[Employees] WITH NOCHECK
ADD CONSTRAINT [FK_Employees_Employees] FOREIGN KEY([ReportsTo])
REFERENCES [dbo].[Employees] ([EmployeeID])
The second-to-last column shows the SQL command I would need to use to delete one of these Foreign Keys, eg:
ALTER TABLE [Employees] DROP CONSTRAINT [FK_Employees_Employees]
...and the right-hand column shows the SQL to create it...
ALTER TABLE [Employees] WITH NOCHECK
ADD CONSTRAINT [FK_Employees_Employees]
FOREIGN KEY([ReportsTo]) REFERENCES [Employees] ([EmployeeID])
With all of these commands, you have everything you need to delete the relevant Foreign Keys to allow you to delete a table, then recreate them later.
Phew. Hope this helps.

The most Simplest one is by using sys.foreign_keys_columns in SQL. Here the table contains the Object ids of all the foreign keys wrt their Referenced column ID Referenced Table ID as well as the Referencing Columns and Tables. As the Id's remains constant the result will be reliable for further modifications in Schema as well as tables.
Query:
SELECT
OBJECT_NAME(fkeys.constraint_object_id) foreign_key_name
,OBJECT_NAME(fkeys.parent_object_id) referencing_table_name
,COL_NAME(fkeys.parent_object_id, fkeys.parent_column_id) referencing_column_name
,OBJECT_SCHEMA_NAME(fkeys.parent_object_id) referencing_schema_name
,OBJECT_NAME (fkeys.referenced_object_id) referenced_table_name
,COL_NAME(fkeys.referenced_object_id, fkeys.referenced_column_id)
referenced_column_name
,OBJECT_SCHEMA_NAME(fkeys.referenced_object_id) referenced_schema_name
FROM sys.foreign_key_columns AS fkeys
We can also add filter by using 'where'
WHERE OBJECT_NAME(fkeys.parent_object_id) = 'table_name' AND
OBJECT_SCHEMA_NAME(fkeys.parent_object_id) = 'schema_name'

SELECT PKTABLE_QUALIFIER = CONVERT(SYSNAME,DB_NAME()),
PKTABLE_OWNER = CONVERT(SYSNAME,SCHEMA_NAME(O1.SCHEMA_ID)),
PKTABLE_NAME = CONVERT(SYSNAME,O1.NAME),
PKCOLUMN_NAME = CONVERT(SYSNAME,C1.NAME),
FKTABLE_QUALIFIER = CONVERT(SYSNAME,DB_NAME()),
FKTABLE_OWNER = CONVERT(SYSNAME,SCHEMA_NAME(O2.SCHEMA_ID)),
FKTABLE_NAME = CONVERT(SYSNAME,O2.NAME),
FKCOLUMN_NAME = CONVERT(SYSNAME,C2.NAME),
-- Force the column to be non-nullable (see SQL BU 325751)
--KEY_SEQ = isnull(convert(smallint,k.constraint_column_id), sysconv(smallint,0)),
UPDATE_RULE = CONVERT(SMALLINT,CASE OBJECTPROPERTY(F.OBJECT_ID,'CnstIsUpdateCascade')
WHEN 1 THEN 0
ELSE 1
END),
DELETE_RULE = CONVERT(SMALLINT,CASE OBJECTPROPERTY(F.OBJECT_ID,'CnstIsDeleteCascade')
WHEN 1 THEN 0
ELSE 1
END),
FK_NAME = CONVERT(SYSNAME,OBJECT_NAME(F.OBJECT_ID)),
PK_NAME = CONVERT(SYSNAME,I.NAME),
DEFERRABILITY = CONVERT(SMALLINT,7) -- SQL_NOT_DEFERRABLE
FROM SYS.ALL_OBJECTS O1,
SYS.ALL_OBJECTS O2,
SYS.ALL_COLUMNS C1,
SYS.ALL_COLUMNS C2,
SYS.FOREIGN_KEYS F
INNER JOIN SYS.FOREIGN_KEY_COLUMNS K
ON (K.CONSTRAINT_OBJECT_ID = F.OBJECT_ID)
INNER JOIN SYS.INDEXES I
ON (F.REFERENCED_OBJECT_ID = I.OBJECT_ID
AND F.KEY_INDEX_ID = I.INDEX_ID)
WHERE O1.OBJECT_ID = F.REFERENCED_OBJECT_ID
AND O2.OBJECT_ID = F.PARENT_OBJECT_ID
AND C1.OBJECT_ID = F.REFERENCED_OBJECT_ID
AND C2.OBJECT_ID = F.PARENT_OBJECT_ID
AND C1.COLUMN_ID = K.REFERENCED_COLUMN_ID
AND C2.COLUMN_ID = K.PARENT_COLUMN_ID

SELECT
object_name(parent_object_id),
object_name(referenced_object_id),
name
FROM sys.foreign_keys
WHERE parent_object_id = object_id('Table Name')

List of all foreign keys referencing a given table in SQL Server :
You can get the referencing table name and column name through following query...
SELECT
OBJECT_NAME(f.parent_object_id) TableName,
COL_NAME(fc.parent_object_id,fc.parent_column_id) ColName
FROM
sys.foreign_keys AS f
INNER JOIN
sys.foreign_key_columns AS fc
ON f.OBJECT_ID = fc.constraint_object_id
INNER JOIN
sys.tables t
ON t.OBJECT_ID = fc.referenced_object_id
WHERE
OBJECT_NAME (f.referenced_object_id) = 'TableName'
And following screenshot for your understanding...

I am using this script to find all details related to foreign key.
I am using INFORMATION.SCHEMA.
Below is a SQL Script:
SELECT
ccu.table_name AS SourceTable
,ccu.constraint_name AS SourceConstraint
,ccu.column_name AS SourceColumn
,kcu.table_name AS TargetTable
,kcu.column_name AS TargetColumn
FROM INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE ccu
INNER JOIN INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS rc
ON ccu.CONSTRAINT_NAME = rc.CONSTRAINT_NAME
INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE kcu
ON kcu.CONSTRAINT_NAME = rc.UNIQUE_CONSTRAINT_NAME
ORDER BY ccu.table_name

First
EXEC sp_fkeys 'Table', 'Schema'
Then use NimbleText to play with your results

Some good answers above. But I prefer to have the answer with one query.
This piece of code is taken from sys.sp_helpconstraint (sys proc)
That's the way Microsoft looks up if there are foreign keys associated to the tbl.
--setup variables. Just change 'Customer' to tbl you want
declare #objid int,
#objname nvarchar(776)
select #objname = 'Customer'
select #objid = object_id(#objname)
if exists (select * from sys.foreign_keys where referenced_object_id = #objid)
select 'Table is referenced by foreign key' =
db_name() + '.'
+ rtrim(schema_name(ObjectProperty(parent_object_id,'schemaid')))
+ '.' + object_name(parent_object_id)
+ ': ' + object_name(object_id)
from sys.foreign_keys
where referenced_object_id = #objid
order by 1
The answer will look like this: test_db_name.dbo.Account: FK_Account_Customer

SELECT OBJECT_NAME(fk.parent_object_id) as ReferencingTable,
OBJECT_NAME(fk.constraint_object_id) as [FKContraint]
FROM sys.foreign_key_columns as fk
WHERE fk.referenced_object_id = OBJECT_ID('ReferencedTable', 'U')
This only shows the relationship if the are foreign key constraints. My database apparently predates the FK constraint.Some table use triggers to enforce referential integrity, and sometimes there's nothing but a similarly named column to indicate the relationship (and no referential integrity at all).
Fortunately, we do have a consistent naming scene so I am able to find referencing tables
and views like this:
SELECT OBJECT_NAME(object_id) from sys.columns where name like 'client_id'
I used this select as the basis for generating a script the does what I need to do on
the related tables.

SELECT
OBJECT_NAME(parent_object_id) 'Parent table',
c.NAME 'Parent column name',
OBJECT_NAME(referenced_object_id) 'Referenced table',
cref.NAME 'Referenced column name'
FROM
sys.foreign_key_columns fkc
INNER JOIN
sys.columns c
ON fkc.parent_column_id = c.column_id
AND fkc.parent_object_id = c.object_id
INNER JOIN
sys.columns cref
ON fkc.referenced_column_id = cref.column_id
AND fkc.referenced_object_id = cref.object_id where OBJECT_NAME(parent_object_id) = 'tablename'
If you want to get the foreign key relation of all the tables exclude the where clause else write your tablename instead of tablename

Most preferable answer by #BankZ
sp_help 'TableName'
additionally for different schema
sp_help 'schemaName.TableName'

Mysql server has information_schema.REFERENTIAL_CONSTRAINTS table FYI, you can filter it by table name or referenced table name.

Working off of what #Gishu did I was able to produce and use the following SQL in SQL Server 2005
SELECT t.name AS TableWithForeignKey, fk.constraint_column_id AS FK_PartNo,
c.name AS ForeignKeyColumn, o.name AS FK_Name
FROM sys.foreign_key_columns AS fk
INNER JOIN sys.tables AS t ON fk.parent_object_id = t.object_id
INNER JOIN sys.columns AS c ON fk.parent_object_id = c.object_id
AND fk.parent_column_id = c.column_id
INNER JOIN sys.objects AS o ON fk.constraint_object_id = o.object_id
WHERE fk.referenced_object_id = (SELECT object_id FROM sys.tables
WHERE name = 'TableOthersForeignKeyInto')
ORDER BY TableWithForeignKey, FK_PartNo;
Which Displays the tables, columns and Foreign Key names all in 1 query.

Determine primary keys and unique keys for all tables in a database...
This should list all the constraints and at the end you can put your filters
/* CAST IS DONE , SO THAT OUTPUT INTEXT FILE REMAINS WITH SCREEN LIMIT*/
WITH ALL_KEYS_IN_TABLE (CONSTRAINT_NAME,CONSTRAINT_TYPE,PARENT_TABLE_NAME,PARENT_COL_NAME,PARENT_COL_NAME_DATA_TYPE,REFERENCE_TABLE_NAME,REFERENCE_COL_NAME)
AS
(
SELECT CONSTRAINT_NAME= CAST (PKnUKEY.name AS VARCHAR(30)) ,
CONSTRAINT_TYPE=CAST (PKnUKEY.type_desc AS VARCHAR(30)) ,
PARENT_TABLE_NAME=CAST (PKnUTable.name AS VARCHAR(30)) ,
PARENT_COL_NAME=CAST ( PKnUKEYCol.name AS VARCHAR(30)) ,
PARENT_COL_NAME_DATA_TYPE= oParentColDtl.DATA_TYPE,
REFERENCE_TABLE_NAME='' ,
REFERENCE_COL_NAME=''
FROM sys.key_constraints as PKnUKEY
INNER JOIN sys.tables as PKnUTable
ON PKnUTable.object_id = PKnUKEY.parent_object_id
INNER JOIN sys.index_columns as PKnUColIdx
ON PKnUColIdx.object_id = PKnUTable.object_id
AND PKnUColIdx.index_id = PKnUKEY.unique_index_id
INNER JOIN sys.columns as PKnUKEYCol
ON PKnUKEYCol.object_id = PKnUTable.object_id
AND PKnUKEYCol.column_id = PKnUColIdx.column_id
INNER JOIN INFORMATION_SCHEMA.COLUMNS oParentColDtl
ON oParentColDtl.TABLE_NAME=PKnUTable.name
AND oParentColDtl.COLUMN_NAME=PKnUKEYCol.name
UNION ALL
SELECT CONSTRAINT_NAME= CAST (oConstraint.name AS VARCHAR(30)) ,
CONSTRAINT_TYPE='FK',
PARENT_TABLE_NAME=CAST (oParent.name AS VARCHAR(30)) ,
PARENT_COL_NAME=CAST ( oParentCol.name AS VARCHAR(30)) ,
PARENT_COL_NAME_DATA_TYPE= oParentColDtl.DATA_TYPE,
REFERENCE_TABLE_NAME=CAST ( oReference.name AS VARCHAR(30)) ,
REFERENCE_COL_NAME=CAST (oReferenceCol.name AS VARCHAR(30))
FROM sys.foreign_key_columns FKC
INNER JOIN sys.sysobjects oConstraint
ON FKC.constraint_object_id=oConstraint.id
INNER JOIN sys.sysobjects oParent
ON FKC.parent_object_id=oParent.id
INNER JOIN sys.all_columns oParentCol
ON FKC.parent_object_id=oParentCol.object_id /* ID of the object to which this column belongs.*/
AND FKC.parent_column_id=oParentCol.column_id/* ID of the column. Is unique within the object.Column IDs might not be sequential.*/
INNER JOIN sys.sysobjects oReference
ON FKC.referenced_object_id=oReference.id
INNER JOIN INFORMATION_SCHEMA.COLUMNS oParentColDtl
ON oParentColDtl.TABLE_NAME=oParent.name
AND oParentColDtl.COLUMN_NAME=oParentCol.name
INNER JOIN sys.all_columns oReferenceCol
ON FKC.referenced_object_id=oReferenceCol.object_id /* ID of the object to which this column belongs.*/
AND FKC.referenced_column_id=oReferenceCol.column_id/* ID of the column. Is unique within the object.Column IDs might not be sequential.*/
)
select * from ALL_KEYS_IN_TABLE
where
PARENT_TABLE_NAME in ('YOUR_TABLE_NAME')
or REFERENCE_TABLE_NAME in ('YOUR_TABLE_NAME')
ORDER BY PARENT_TABLE_NAME,CONSTRAINT_NAME;
For reference please read thru - http://blogs.msdn.com/b/sqltips/archive/2005/09/16/469136.aspx

I have been using this on 2008 and up. It's similar to some other solutions listed but, the field names are proper cased to handle case specific (LatBin) collations. Additionally, you can feed it a single table name and retrieve just the info for that table.
-->>SPECIFY THE DESIRED DB
USE ???
GO
/*********************************************************************************************
LIST OUT ALL PRIMARY AND FOREIGN KEY CONSTRAINTS IN A DB OR FOR A SPECIFIED TABLE
*********************************************************************************************/
DECLARE #tblName VARCHAR(255)
/*******************/
SET #tblName = NULL-->NULL will return all PK/FK constraints for every table in the database
/*******************/
SELECT PKTABLE_QUALIFIER = CONVERT(SYSNAME,DB_NAME()),
PKTABLE_OWNER = CONVERT(SYSNAME,SCHEMA_NAME(O1.schema_id)),
PKTABLE_NAME = CONVERT(SYSNAME,O1.name),
PKCOLUMN_NAME = CONVERT(SYSNAME,C1.name),
FKTABLE_QUALIFIER = CONVERT(SYSNAME,DB_NAME()),
FKTABLE_OWNER = CONVERT(SYSNAME,SCHEMA_NAME(O2.schema_id)),
FKTABLE_NAME = CONVERT(SYSNAME,O2.name),
FKCOLUMN_NAME = CONVERT(SYSNAME,C2.name),
-- Force the column to be non-nullable (see SQL BU 325751)
KEY_SEQ = isnull(convert(smallint,K.constraint_column_id),0),
UPDATE_RULE = CONVERT(SMALLINT,CASE OBJECTPROPERTY(F.object_id,'CnstIsUpdateCascade')
WHEN 1 THEN 0
ELSE 1
END),
DELETE_RULE = CONVERT(SMALLINT,CASE OBJECTPROPERTY(F.object_id,'CnstIsDeleteCascade')
WHEN 1 THEN 0
ELSE 1
END),
FK_NAME = CONVERT(SYSNAME,OBJECT_NAME(F.object_id)),
PK_NAME = CONVERT(SYSNAME,I.name),
DEFERRABILITY = CONVERT(SMALLINT,7) -- SQL_NOT_DEFERRABLE
FROM sys.all_objects O1,
sys.all_objects O2,
sys.all_columns C1,
sys.all_columns C2,
sys.foreign_keys F
INNER JOIN sys.foreign_key_columns K
ON (K.constraint_object_id = F.object_id)
INNER JOIN sys.indexes I
ON (F.referenced_object_id = I.object_id
AND F.key_index_id = I.index_id)
WHERE O1.object_id = F.referenced_object_id
AND O2.object_id = F.parent_object_id
AND C1.object_id = F.referenced_object_id
AND C2.object_id = F.parent_object_id
AND C1.column_id = K.referenced_column_id
AND C2.column_id = K.parent_column_id
AND ( O1.name = #tblName
OR O2.name = #tblName
OR #tblName IS null)
ORDER BY PKTABLE_NAME,FKTABLE_NAME

This gets any foreign key that involves the chosen table. *Assumes a _FIRSTABLENAME_SECONDTABLENAME format.
declare #tablename as varchar(MAX)
SET #tablename = 'yourtablename'
SELECT name
FROM YOURDATABASE.sys.objects
WHERE type_desc = 'FOREIGN_KEY_CONSTRAINT' and (name LIKE '%_' + #tablename + 'empdb_%' or name LIKE '%_' + #tablename )
This is a more general form:
SELECT name
FROM YOURDATABASE_PROD.sys.objects
WHERE type_desc = 'FOREIGN_KEY_CONSTRAINT' and name LIKE '%' + #tablename + '%' and
name NOT LIKE '[a-zA-Z0-9]' + #tablename + '%' and name NOT LIKE '%' + #tablename + '[a-zA-Z0-9]'

There is how to get count of all responsibilities for selected Id. Just change #dbTableName value, #dbRowId value and its type (if int you need to remove '' in line no 82 (..SET #SQL = ..)). Enjoy.
DECLARE #dbTableName varchar(max) = 'User'
DECLARE #dbRowId uniqueidentifier = '21d34ecd-c1fd-11e2-8545-002219a42e1c'
DECLARE #FK_ROWCOUNT int
DECLARE #SQL nvarchar(max)
DECLARE #PKTABLE_QUALIFIER sysname
DECLARE #PKTABLE_OWNER sysname
DECLARE #PKTABLE_NAME sysname
DECLARE #PKCOLUMN_NAME sysname
DECLARE #FKTABLE_QUALIFIER sysname
DECLARE #FKTABLE_OWNER sysname
DECLARE #FKTABLE_NAME sysname
DECLARE #FKCOLUMN_NAME sysname
DECLARE #UPDATE_RULE smallint
DECLARE #DELETE_RULE smallint
DECLARE #FK_NAME sysname
DECLARE #PK_NAME sysname
DECLARE #DEFERRABILITY sysname
IF OBJECT_ID('tempdb..#Temp1') IS NOT NULL
DROP TABLE #Temp1;
CREATE TABLE #Temp1 (
PKTABLE_QUALIFIER sysname,
PKTABLE_OWNER sysname,
PKTABLE_NAME sysname,
PKCOLUMN_NAME sysname,
FKTABLE_QUALIFIER sysname,
FKTABLE_OWNER sysname,
FKTABLE_NAME sysname,
FKCOLUMN_NAME sysname,
UPDATE_RULE smallint,
DELETE_RULE smallint,
FK_NAME sysname,
PK_NAME sysname,
DEFERRABILITY sysname,
FK_ROWCOUNT int
);
DECLARE FK_Counter_Cursor CURSOR FOR
SELECT PKTABLE_QUALIFIER = CONVERT(SYSNAME,DB_NAME()),
PKTABLE_OWNER = CONVERT(SYSNAME,SCHEMA_NAME(O1.SCHEMA_ID)),
PKTABLE_NAME = CONVERT(SYSNAME,O1.NAME),
PKCOLUMN_NAME = CONVERT(SYSNAME,C1.NAME),
FKTABLE_QUALIFIER = CONVERT(SYSNAME,DB_NAME()),
FKTABLE_OWNER = CONVERT(SYSNAME,SCHEMA_NAME(O2.SCHEMA_ID)),
FKTABLE_NAME = CONVERT(SYSNAME,O2.NAME),
FKCOLUMN_NAME = CONVERT(SYSNAME,C2.NAME),
-- Force the column to be non-nullable (see SQL BU 325751)
--KEY_SEQ = isnull(convert(smallint,k.constraint_column_id), sysconv(smallint,0)),
UPDATE_RULE = CONVERT(SMALLINT,CASE OBJECTPROPERTY(F.OBJECT_ID,'CnstIsUpdateCascade')
WHEN 1 THEN 0
ELSE 1
END),
DELETE_RULE = CONVERT(SMALLINT,CASE OBJECTPROPERTY(F.OBJECT_ID,'CnstIsDeleteCascade')
WHEN 1 THEN 0
ELSE 1
END),
FK_NAME = CONVERT(SYSNAME,OBJECT_NAME(F.OBJECT_ID)),
PK_NAME = CONVERT(SYSNAME,I.NAME),
DEFERRABILITY = CONVERT(SMALLINT,7) -- SQL_NOT_DEFERRABLE
FROM SYS.ALL_OBJECTS O1,
SYS.ALL_OBJECTS O2,
SYS.ALL_COLUMNS C1,
SYS.ALL_COLUMNS C2,
SYS.FOREIGN_KEYS F
INNER JOIN SYS.FOREIGN_KEY_COLUMNS K
ON (K.CONSTRAINT_OBJECT_ID = F.OBJECT_ID)
INNER JOIN SYS.INDEXES I
ON (F.REFERENCED_OBJECT_ID = I.OBJECT_ID
AND F.KEY_INDEX_ID = I.INDEX_ID)
WHERE O1.OBJECT_ID = F.REFERENCED_OBJECT_ID
AND O2.OBJECT_ID = F.PARENT_OBJECT_ID
AND C1.OBJECT_ID = F.REFERENCED_OBJECT_ID
AND C2.OBJECT_ID = F.PARENT_OBJECT_ID
AND C1.COLUMN_ID = K.REFERENCED_COLUMN_ID
AND C2.COLUMN_ID = K.PARENT_COLUMN_ID
AND O1.NAME = #dbTableName
OPEN FK_Counter_Cursor;
FETCH NEXT FROM FK_Counter_Cursor INTO #PKTABLE_QUALIFIER, #PKTABLE_OWNER, #PKTABLE_NAME, #PKCOLUMN_NAME, #FKTABLE_QUALIFIER, #FKTABLE_OWNER, #FKTABLE_NAME, #FKCOLUMN_NAME, #UPDATE_RULE, #DELETE_RULE, #FK_NAME, #PK_NAME, #DEFERRABILITY;
WHILE ##FETCH_STATUS = 0
BEGIN
SET #SQL = 'SELECT #dbCountOut = COUNT(*) FROM [' + #FKTABLE_NAME + '] WHERE [' + #FKCOLUMN_NAME + '] = ''' + CAST(#dbRowId AS varchar(max)) + '''';
EXECUTE sp_executesql #SQL, N'#dbCountOut int OUTPUT', #dbCountOut = #FK_ROWCOUNT OUTPUT;
INSERT INTO #Temp1 (PKTABLE_QUALIFIER, PKTABLE_OWNER, PKTABLE_NAME, PKCOLUMN_NAME, FKTABLE_QUALIFIER, FKTABLE_OWNER, FKTABLE_NAME, FKCOLUMN_NAME, UPDATE_RULE, DELETE_RULE, FK_NAME, PK_NAME, DEFERRABILITY, FK_ROWCOUNT) VALUES (#FKTABLE_QUALIFIER, #PKTABLE_OWNER, #PKTABLE_NAME, #PKCOLUMN_NAME, #FKTABLE_QUALIFIER, #FKTABLE_OWNER, #FKTABLE_NAME, #FKCOLUMN_NAME, #UPDATE_RULE, #DELETE_RULE, #FK_NAME, #PK_NAME, #DEFERRABILITY, #FK_ROWCOUNT)
FETCH NEXT FROM FK_Counter_Cursor INTO #PKTABLE_QUALIFIER, #PKTABLE_OWNER, #PKTABLE_NAME, #PKCOLUMN_NAME, #FKTABLE_QUALIFIER, #FKTABLE_OWNER, #FKTABLE_NAME, #FKCOLUMN_NAME, #UPDATE_RULE, #DELETE_RULE, #FK_NAME, #PK_NAME, #DEFERRABILITY;
END;
CLOSE FK_Counter_Cursor;
DEALLOCATE FK_Counter_Cursor;
GO
SELECT * FROM #Temp1
GO

The following solution work for me:
--Eliminar las llaves foraneas
declare #query varchar(8000)
declare cursorRecorrerTabla cursor for
SELECT 'ALTER TABLE [PoaComFinH].['+sch.name+'].['+referencingTable.Name+'] DROP CONSTRAINT ['+foreignKey.name+']' 'query'
FROM PoaComFinH.sys.foreign_key_columns fk
JOIN PoaComFinH.sys.tables referencingTable ON fk.parent_object_id = referencingTable.object_id
JOIN PoaComFinH.sys.schemas sch ON referencingTable.schema_id = sch.schema_id
JOIN PoaComFinH.sys.objects foreignKey ON foreignKey.object_id = fk.constraint_object_id
JOIN PoaComFinH.sys.tables referencedTable ON fk.referenced_object_id = referencedTable.object_id
--3ro. abrir el cursor.
open cursorRecorrerTabla
fetch next from cursorRecorrerTabla
into #query
while ##fetch_status = 0
begin
--inicio cuerpo del cursor
print #query
exec(#query)
--fin cuerpo del cursor
fetch next from cursorRecorrerTabla
into #query
end
--cerrar cursor
close cursorRecorrerTabla
deallocate cursorRecorrerTabla

You can find through below query :
SELECT OBJECT_NAME (FK.referenced_object_id) 'Referenced Table',
OBJECT_NAME(FK.parent_object_id) 'Referring Table', FK.name 'Foreign Key',
COL_NAME(FK.referenced_object_id, FKC.referenced_column_id) 'Referenced Column',
COL_NAME(FK.parent_object_id,FKC.parent_column_id) 'Referring Column'
FROM sys.foreign_keys AS FK
INNER JOIN sys.foreign_key_columns AS FKC
ON FKC.constraint_object_id = FK.OBJECT_ID
WHERE OBJECT_NAME (FK.referenced_object_id) = 'YourTableName'
AND COL_NAME(FK.referenced_object_id, FKC.referenced_column_id) = 'YourColumnName'
order by OBJECT_NAME(FK.parent_object_id)

Also try.
EXEC sp_fkeys 'tableName', 'schemaName'
with sp_fkeys you may filter the result by not only pk table name and schema but also with fk table name and schema. link

with tab_list as (
select t.name AS Table_Name, t.object_id, s.name AS Table_Schema from sys.tables t, sys.schemas s
where t.schema_id = s.schema_id
and s.name = 'your schema')
select IIF(col.column_id = 1, tab.TABLE_SCHEMA + '.' + tab.TABLE_NAME, NULL) Table_Name,
col.Name AS Column_Name, IIF(col.IS_NULLABLE= 0, 'NOT NULL', '') Nullable, st.name Type,
CASE WHEN st.name = 'decimal' THEN CONVERT(NVARCHAR(4000), col.Precision) + ',' + CONVERT(NVARCHAR(4000), col.Scale)
WHEN col.max_length = -1 THEN 'max'
WHEN st.name in ('int', 'bit', 'bigint', 'datetime2') THEN NULL
ELSE CONVERT(NVARCHAR(4000), col.max_length / 2)
END
AS Length,
ss.name + '.' + stab.name Referenced_Table, scol.name Referenced_Column
from sys.COLUMNS col
INNER JOIN tab_list tab ON col.object_id = tab.object_id
INNER JOIN sys.types st ON col.system_type_id = st.system_type_id AND col.user_type_id = st.user_type_id
LEFT JOIN [sys].[foreign_key_columns] sfkc ON col.object_id = sfkc.parent_object_id AND col.column_id = sfkc.parent_column_id
LEFT JOIN sys.tables stab ON sfkc.referenced_object_id = stab.object_id
LEFT JOIN sys.columns scol ON sfkc.referenced_object_id = scol.object_id AND sfkc.referenced_column_id = scol.column_id
LEFT JOIN sys.schemas ss ON ss.schema_id = stab.schema_id

Here is the best practice in my opinion to work over this scenario in SQL Server 2016.
You have to list the foreign keys using :
EXEC sp_fkeys 'TableName'
There you can see the full info of the FKs. Notice the columns FKTABLE_NAME, FKCOLUMN_NAME, FK_NAME, UPDATE_RULE, DELETE_RULE is the info you need to remove foreign keys and implement them again after truncate.
You can organise a script as follows:
-- EXEC sp_fkeys 'TableName'
-- DROP CONSTRAINTS: I drop one, here drop every constraint you desire.
BEGIN TRANSACTION
GO
ALTER TABLE dbo.TableName
DROP CONSTRAINT IF EXISTS FK_TableName_OtherTable
GO
ALTER TABLE dbo.TableName SET (LOCK_ESCALATION = TABLE)
GO
COMMIT
-- TRUNCATE
BEGIN TRANSACTION
TRUNCATE TABLE TableName
GO
COMMIT
-- RECREATE CONSTRAINTS: I recreate 1, here recreate every fk you desire
BEGIN TRANSACTION
GO
ALTER TABLE dbo.TableName SET (LOCK_ESCALATION = TABLE)
GO
ALTER TABLE dbo.TableName ADD CONSTRAINT
FK_TableName_OtherTable FOREIGN KEY
(
Id_FK
) REFERENCES dbo.OtherTable
(
Id
) ON UPDATE NO ACTION
ON DELETE NO ACTION
GO
COMMIT
** Values for UPDATE_RULE and DELETE_RULE can be seen in documentation of sp_fkeys:

I know that its a late(very late) reply, but I find these easy ways to find all the foreign_key_references. Here're the solutions;
Solution 01:
EXEC SP_FKEYS 'MyTableName'; // It'll show you the all the information(in multiple tables) regarding to the TableName with all ForeignKey_References.
Solution 02:
EXEC SP_HELP 'MyTableName'; // It'll show all ForeignKey references in a single table.
Solution 03:
// It'll show you the Column_Name with Referenced_Table_Name
SELECT
COL_NAME(fc.parent_object_id,fc.parent_column_id) Column_Name,
OBJECT_NAME(f.parent_object_id) Table_Name
FROM
sys.foreign_keys AS f
INNER JOIN
sys.foreign_key_columns AS fc
ON f.OBJECT_ID = fc.constraint_object_id
INNER JOIN
sys.tables t
ON t.OBJECT_ID = fc.referenced_object_id
WHERE
OBJECT_NAME (f.referenced_object_id) = 'MyTableName'
Hopefully, this'll help you a lot. ;-)

This answer builds on but is formatted like sp_fkeys, works on multiple columns and lists their order.
SELECT fk_obj.name AS FK_NAME,
pk_schema.name AS PKTABLE_OWNER,
pk_table.name AS PKTABLE_NAME,
pk_column.name AS PKCOLUMN_NAME,
fk_schema.name AS FKTABLE_OWNER,
fk_table.name AS FKTABLE_NAME,
fk_column.name AS FKCOLUMN_NAME,
ROW_NUMBER() over (
PARTITION BY fk_obj.name, fk_schema.name
ORDER BY fkc.constraint_column_id
) AS KEY_SEQ
FROM sys.foreign_key_columns fkc
INNER JOIN sys.objects fk_obj
ON fk_obj.object_id = fkc.constraint_object_id
INNER JOIN sys.tables fk_table
ON fk_table.object_id = fkc.parent_object_id
INNER JOIN sys.schemas fk_schema
ON fk_table.schema_id = fk_schema.schema_id
INNER JOIN sys.columns fk_column
ON fk_column.column_id = parent_column_id
AND fk_column.object_id = fk_table.object_id
INNER JOIN sys.tables pk_table
ON pk_table.object_id = fkc.referenced_object_id
INNER JOIN sys.schemas pk_schema
ON pk_table.schema_id = pk_schema.schema_id
INNER JOIN sys.columns pk_column
ON pk_column.column_id = fkc.referenced_column_id
AND pk_column.object_id = pk_table.object_id;