How to check if the Default Value Constraint exists? - sql

Question

I am using SQL server 2008. I need to find if default value constraint does not exist then create it. Here is what I have tried.
IF (NOT EXISTS(SELECT * FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS WHERE CONSTRAINT_NAME ='MyConstraint'))
BEGIN
ALTER TABLE [XX] ADD CONSTRAINT [MyConstraint] DEFAULT ((-1)) FOR [XXXX]
END
GO

Answer 1

if not exists (
select *
from sys.all_columns c
join sys.tables t on t.object_id = c.object_id
join sys.schemas s on s.schema_id = t.schema_id
join sys.default_constraints d on c.default_object_id = d.object_id
where t.name = 'table'
and c.name = 'column'
and s.name = 'schema')
....

Answer 2

I find this to be easier:
IF OBJECT_ID('SchemaName.MyConstraint', 'D') IS NULL
BEGIN
-- create it here
END

Answer 3

I was a bit puzzled as to why this simple task was so complicated. In my case, I don't have constraint names - only table and column names. I want to check if they already have a default before trying to add one.
After a bit more digging, I came up with this:
IF (SELECT Column_Default FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = 'MY_TABLE' AND COLUMN_NAME = 'MY_COLUMN') is NULL
BEGIN
ALTER TABLE [dbo].[MY_TABLE]
ADD DEFAULT ('') FOR [MY_COLUMN]
END
GO
I have to implement this in a ginormous boilerplate script, so the shorter the better.

Answer 4

if not exists(select 1 from sys.default_constraints where name = 'SchemaName.MyConstraint')
begin
-- create it here
end

Answer 5

The following works for me on SQL Server 2016.
Assuming I have a table named MY_TABLE and a column MY_COLIUMN.
I would like to add a constrain (default to '-1' ) on MY_COLIUMN that need to add the constrain on.
/* Test for the specific column */
IF EXISTS (select 1 from sys.all_columns c where c.object_id= OBJECT_ID(N'MY_TABLE') and c.name='MY_COLIUMN')
BEGIN
/* Add default if not exits */
IF NOT EXISTS (
select 1 from sys.default_constraints c where c.object_id =
(
select default_object_id from sys.all_columns c where c.object_id = OBJECT_ID(N'MY_TABLE') and c.name='MY_COLIUMN'
)
)
BEGIN
ALTER TABLE MY_TABLE
ADD DEFAULT '-1' FOR MY_COLIUMN;
END
END
GO

Answer 6

I've used the following in the past:
DECLARE #default sysname
SELECT #default = object_name( cdefault ) FROM syscolumns WHERE id = object_id( 'DBO.TABLE' ) AND name = 'COLUMN'
IF ( not #default is null )
BEGIN
...
END

Answer 7

Search the system table where the default costraints of the database are stored, without the schema name:
IF EXISTS(SELECT 1 FROM sys.default_constraints WHERE [name] = 'MyConstraint')
print 'Costraint exists!';
ELSE
print 'Costraint doesn''t exist!';

Answer 8

I know I'm coming to the party late here, but I am a big fan of OBJECTPROPERTY. Here is how to set a default of 1 on a column if the default does not yet exist.
IF (OBJECTPROPERTY(OBJECT_ID('My_constraint_name'),'CnstIsColumn') IS NULL
ALTER TABLE Mytable ADD CONSTRAINT [MY_constraint_name] DEFAULT ((1)) FOR [My_column_name]