Let's say I have an empty table with 5 columns and a large number of tables with a random selection of those 5 columns. How can I insert the columns that are present in smaller tables into the corresponding columns in the large table?
For Example:
Table A has columns 1, 2, 3, 4, 5
Table B has columns 1, 2, 5
I want to insert the values of table B into the corresponding columns of A, and leave columns 3 and 4 in A as NULL.
I know this is not a good way to use SQL, don't ask how I got into this mess!
I have tried:
CASE WHEN COL_LENGTH('MyTable', 'MyColumn') IS NOT NULL THEN MyColumn ELSE NULL END
but I get an error "Invalid column name", even though SQL doesn't have to use the (non-existant) column.
Any suggestions?
List the columns when you insert:
insert into a (col1, col2, col5)
select col1, col2, col5
from b;
Assuming that col3 and col4 allow NULL values and have no DEFAULT (or the default is NULL), then these are populated with NULL values for all rows inserted by the statement.
You need to utilize dynamic SQL. With the below script, you dynamically get the parameter list from the system table where columns from table A match table B. Then you build your dynamic SQL statement and execute it.
The code below currently will PRINT the SQL statement; however, once you are satisfied, you can comment out the PRINT(#SQL) and comment back in the EXECUTE(#SQL)
DECLARE #TableAName VARCHAR(100)
,#TableBName VARCHAR(100);
SET #TableAName = 'TableA';
SET #TableBName = 'TableB';
DECLARE #Parameter VARCHAR(1000) = ''
,#SQL VARCHAR(8000)
,#TBLASchema VARCHAR(100)
,#TBLBSchema VARCHAR(100)
,#DatabaseName VARCHAR(100);
SET #TBLASchema = (SELECT OBJECT_SCHEMA_NAME(T.object_id)
FROM sys.tables AS T
WHERE T.name = #TableAName);
SET #TBLBSchema = (SELECT OBJECT_SCHEMA_NAME(T.object_id)
FROM sys.tables AS T
WHERE T.name = #TableBName);
SET #DatabaseName = DB_NAME();
SELECT #Parameter = #Parameter + ',[' + TBL_COLS.name + ']'
FROM sys.tables AS T
JOIN sys.columns AS TBL_COLS
ON T.[object_id] = TBL_COLS.[object_id]
AND T.name = #TableAName
WHERE TBL_COLS.name IN (SELECT TBL2_COLS.name
FROM sys.tables AS T
JOIN sys.columns AS TBL2_COLS
ON T.[object_id] = TBL2_COLS.[object_id]
AND T.name = #TableBName);
SET #Parameter = SUBSTRING(#Parameter,2,LEN(#Parameter)-1);
SET #SQL = 'INSERT INTO [' + #DatabaseName + '].[' + #TBLASchema + '].[' + #TableAName + '] '
+ '(' + #Parameter + ')'
+ ' SELECT ' + #Parameter
+ ' FROM [' + #DatabaseName + '].[' + #TBLBSchema + '].[' + #TableBName + '];'
PRINT(#SQL);
--EXECUTE(#SQL);
Related
I've created the script below to be able to quickly create a minimal reproducible example for other questions in general.
This script uses an original table and generates the following PRINT statements:
DROP and CREATE a temp table with structure matching the original table
INSERT INTO statement using examples from the actual data
I can just add the original table name into the variable listed, along with the number of sample records required from the table. When I run it, it generates all of the statements needed in the Messages window in SSMS. Then I can just copy and paste those statements into my posted questions, so those answering have something to work with.
I know that you can get similar results in SSMS through Tasks>Generate Scripts, but this gets things down to the minimal amount of code that's useful for posting here without all of the unnecessary info that SSMS generates automatically. It's just a quick way to create a reproduced version of a simple table with actual sample data in it.
Unfortunately the one scenario that doesn't work is if I run it on very wide tables. It seems to fail on the last STRING_AGG() query where it's building the VALUES portion of the INSERT. When it runs on wide tables, it returns NULL.
Any suggestions to correct this?
EDIT: I figured out the issue I was having with UNIQUEIDENTIFIER columns and revised the query below. Also included an initial check to make sure the table actually exists.
/* ---------------------------------------
-- For creating minimal reproducible examples
-- based on original table and data,
-- builds the following statements
-- -- CREATE temp table with structure matching original table
-- -- INSERT statements based on actual data
--
-- Note: May not work for very wide tables due to limitations on
-- PRINT statements
*/ ---------------------------------------
DECLARE #tableName NVARCHAR(MAX) = 'testTable', -- original table name HERE
#recordCount INT = 5, -- top number of records to insert to temp table
#buildStmt NVARCHAR(MAX),
#insertStmt NVARCHAR(MAX),
#valuesStmt NVARCHAR(MAX),
#insertCol NVARCHAR(MAX),
#strAgg NVARCHAR(MAX),
#insertOutput NVARCHAR(MAX)
IF (EXISTS (SELECT 1 FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = #tableName))
BEGIN
-- build DROP and CREATE statements for temp table from original table
SET #buildStmt = 'IF OBJECT_ID(''tempdb..#' + #tableName + ''') IS NOT NULL DROP TABLE #' + #tableName + CHAR(10) + CHAR(10) +
'CREATE TABLE #' + #tableName + ' (' + CHAR(10)
SELECT #buildStmt = #buildStmt + ' ' + C.[Name] + ' ' +
T.[Name] +
CASE WHEN T.[Name] IN ('varchar','varchar','char','nchar') THEN '(' + CAST(C.[Length] AS VARCHAR) + ') ' ELSE ' ' END +
'NULL,' + CHAR(10)
FROM sysobjects O
JOIN syscolumns C ON C.id = O.id
JOIN systypes T ON T.xusertype = C.xusertype
WHERE O.[name] = #TableName
ORDER BY C.ColID
SET #buildStmt = SUBSTRING(#buildStmt,1,LEN(#buildStmt) - 2) + CHAR(10) + ')' + CHAR(10)
PRINT #buildStmt
-- build INSERT INTO statement from original table
SELECT #insertStmt = 'INSERT INTO #' + #tableName + ' (' +
STUFF ((
SELECT ', [' + C.[Name] + ']'
FROM sysobjects O
JOIN syscolumns C ON C.id = O.id
WHERE O.[name] = #TableName
ORDER BY C.ColID
FOR XML PATH('')), 1, 1, '')
+')'
PRINT #insertStmt
-- build VALUES portion of INSERT from data in original table
SELECT #insertCol = STUFF ((
SELECT '''''''''+CONVERT(NVARCHAR(200),' +
'[' + C.[Name] + ']' +
')+'''''',''+'
FROM sysobjects O
JOIN syscolumns C ON C.id = O.id
JOIN systypes T ON T.xusertype = C.xusertype
WHERE O.[name] = #TableName
ORDER BY C.ColID
FOR XML PATH('')), 1, 1, '')
SET #insertCol = SUBSTRING(#insertCol,1,LEN(#insertCol) - 1)
SELECT #strAgg = ';WITH CTE AS (SELECT TOP(' + CONVERT(VARCHAR,#recordCount) + ') * FROM ' + #tableName + ') ' +
' SELECT #valuesStmt = STRING_AGG(CAST(''' + #insertCol + ' AS NVARCHAR(MAX)),''), ('') ' +
' FROM CTE'
EXEC sp_executesql #strAgg,N'#valuesStmt NVARCHAR(MAX) OUTPUT', #valuesStmt OUTPUT
PRINT 'VALUES (' +REPLACE(SUBSTRING(#valuesStmt,1,LEN(#valuesStmt) - 1),',)',')') + ')'
END
ELSE
BEGIN
PRINT 'Table does NOT exist'
END
I am hoping someone could help or provide insight. I am working on automating the way we audit our database views. The goal is to quickly see which columns are empty in which views. I started to work on a script but ran into different issues. All of the examples with this script run, but produce results that I did not intended. Right now some column headers have titles with a space in between.
Since I am fairly new to this, I am unsure what I am doing wrong or even how to obtain the results I am looking for.
Thank you in advance for your help!
Example 1 - Runs but produces Nulls
Example 2 - Runs but produces 0s,
Example 3 – Runs and produces counts for the entire view rather than
for the column itself (i.e. it gave the max amount of rows in the
view).
------------------------------------
-- EXAMPLE 1:
-- Did not produce the results expected.
-- Issue is it returns all as NULL
---------------------------------------\
DROP TABLE IF EXISTS #tempColumnCount;
CREATE TABLE #tempColumnCount
(
Name VARCHAR(100),
Row_Count INT
);
Declare #SQL VARCHAR(MAX)
SET #SQL = ''
SELECT #SQL = #SQL + 'INSERT INTO #tempColumnCount SELECT ''' + c.name + ''' as Name, SUM (CASE WHEN ''' + c.name +
''' IS NULL THEN 1 END) FROM ' + schema_name(v.schema_id) + '.' + OBJECT_NAME(c.object_id) +
CHAR(13)
FROM sys.columns c
JOIN sys.views v
ON v.object_id = c.object_id AND SCHEMA_NAME(v.schema_id)='analytics'
exec (#SQL)
SELECT Name, Row_Count
FROM #tempColumnCount
---------------------------------------\
-- Example 2: Issue is it returns all as 0
---------------------------------------\
DROP TABLE IF EXISTS #tempColumnCount;
CREATE TABLE #tempColumnCount
(
Name VARCHAR(100),
Row_Count INT
);
Declare #SQL VARCHAR(MAX)
SET #SQL = ''
SELECT #SQL = #SQL + 'INSERT INTO #tempColumnCount SELECT ''' + c.name + ''' as Name, COUNT(1) - COUNT(''' + c.name +
''' ) FROM ' + schema_name(v.schema_id) + '.' + OBJECT_NAME(c.object_id) +
CHAR(13)
FROM sys.columns c
JOIN sys.views v
ON v.object_id = c.object_id AND SCHEMA_NAME(v.schema_id)='analytics'
exec (#SQL)
SELECT Name, Row_Count
FROM #tempColumnCount
---------------------------------------\
-- Example 3: Issue is it returns the the max amount of rows for each column. Which just means it returns the row count for the whole view and not the column it self.
---------------------------------------\
DROP TABLE IF EXISTS #tempColumnCount;
CREATE TABLE #tempColumnCount
(
Name VARCHAR(100),
Row_Count INT
);
Declare #SQL VARCHAR(MAX)
SET #SQL = ''
SELECT #SQL = #SQL + 'INSERT INTO #tempColumnCount SELECT ''' + c.name + ''' as Name, COUNT(''' + c.name +
''' ) FROM ' + schema_name(v.schema_id) + '.' + OBJECT_NAME(c.object_id) +
CHAR(13)
FROM sys.columns c
JOIN sys.views v
ON v.object_id = c.object_id AND SCHEMA_NAME(v.schema_id)='analytics'
exec (#SQL)
SELECT Name, Row_Count
FROM #tempColumnCount
I have a table which has more than 30 columns(all are varchar). I need to list out all the columns which contains blank i.e.' ' values.
I tried using 'coalesce' but it is only for NULL.
The following query will give you all the columns in a table that might have null or '' values.
It is written so that you can run it for all tables in your database but you can limit it to a single table, as I have done for this specific example, checking a table called testingNulls:
--two variables needed for table name and column name, when looping through all tables
declare #table varchar(255), #col varchar(255), #sql varchar(max)
--this will be used to store the result, to have one result set instead of one row per each cursor cycle
if object_id('tempdb..#nullcolumns') is not null drop table #nullcolumns
create table #nullcolumns (tablename varchar(255), columnname varchar(255))
declare getinfo cursor for
select t.name tablename, c.name
from sys.tables t join sys.columns c on t.object_id = c.object_id
where t.name = 'testingnulls' --here the condition for the table name
open getinfo
fetch next from getinfo into #table, #col
while ##fetch_status = 0
begin
select #sql = 'if exists (select top 1 * from [' + #table + '] where [' + #col + '] is null or [' + #col + '] like '''' ) begin insert into #nullcolumns select ''' + #table + ''' as tablename, ''' + #col + ''' as all_nulls end'
print(#sql)
exec(#sql)
fetch next from getinfo into #table, #col
end
close getinfo
deallocate getinfo
--this should be the result you need:
select * from #nullcolumns
You can see a working example here. I hope this is what you need.
List all columns that contain a blank in some record? You'd use a query per column and collect the results with UNION ALL:
select 'COL1' where exists (select * from mytable where col1 like '% %')
union all
select 'COL2' where exists (select * from mytable where col2 like '% %')
union all
...
union all
select 'COL30' where exists (select * from mytable where col30 like '% %');
If you want like select * from [your_table_name] where [col1] = '' and [col2] = ''....., then use dynamic sql query like below.
Query
declare #sql as varchar(max);
select #sql = 'select * from [your_table_name] where '
+ stuff((
select ' and [' + [column_name] + '] = ' + char(39) + char(39)
from information_schema.columns
where table_name = 'your_table_name'
for xml path('')
)
, 1, 5, ''
);
exec(#sql);
Update
Or else if you want to list the column names which have a blank value, then you can use the below dynamic sql query.
Query
declare #sql as varchar(max);
select #sql = stuff((
select ' union all select ' + [column_name] + ' as [col1], '
+ char(39) + [column_name] + char(39) + ' as [col2]'
+ ' from your_table_name'
from information_schema.columns
where table_name = 'your_table_name'
for xml path('')
)
, 1, 11, ''
);
set #sql = 'select distinct t.col2 as [blank_cols] from(' + #sql
+ ')t
where coalesce(ltrim(rtrim(t.col1)), ' + char(39) + char(39) + ') = '
+ char(39) + char(39) + ';';
exec(#sql);
Find a demo here
But still I'm not sure that this is what you are looking out for.
you have not many choices but to specify all the columns in your where clause
WHERE COL1 = '' AND COL2 = '' AND COL3 = '' AND . . .
or you can use Dynamic SQL to form your query, but that is not an easy path to go
If you want to count number of columns having '' value in a table (not for each row) then use the following
SELECT max(CASE WHEN col1 = '' THEN 1 ELSE 0 END) +
max(CASE WHEN col2 = '' THEN 1 ELSE 0 END) +
max(CASE WHEN col3 = '' THEN 1 ELSE 0 END) +
...
FROM t
demo
I created a dynamic SQL script that you can use by providing the table name only
Here it is
declare #sql nvarchar(max)
declare #table sysname = 'ProductAttributes'
select #sql =
'select * from ' + #table + ' where ' +
string_agg('[' + name + '] = '' '' ', ' and ')
from sys.columns
where object_id = OBJECT_ID(#table)
select #sql
exec sp_executesql #sql
Unfortunately, for SQL string concatenation String_Agg function is new with SQL Server 2017
But it is also possible to use SQL XML Path to concatenate WHERE clause fragments
SELECT #sql = 'select * from ' + #table + ' where ' +
STUFF(
(
SELECT
' and ' + '[' + [name] + '] = '' '' '
from sys.columns
where object_id = OBJECT_ID(#table)
FOR XML PATH(''),TYPE
).value('.','VARCHAR(MAX)'
), 1, 5, ''
)
select #sql as sqlscript
exec sp_executesql #sql
I have table name as #Table_Name
I have column value as #Value but don't have the column name (but that exist at 1st position and can be Seek_id or prov_id ...I have to compare my value with this id )
How can I compare that table column name value ?
I want something like
SELECT * FROM #Table_Name
WHERE Table.Column[1].Value = #Value
for example #Table_Name = bb_match and #Value = 6
Possible this be helpful for you -
Query:
IF OBJECT_ID (N'dbo.bb_match') IS NOT NULL
DROP TABLE dbo.bb_match
CREATE TABLE dbo.bb_match (seek_id INT, prov_id INT)
INSERT INTO dbo.bb_match (seek_id, prov_id)
VALUES (6, 1), (2, 6)
DECLARE
#ColumnID TINYINT
, #Value INT
, #TableName SYSNAME
, #SQL NVARCHAR(500)
SELECT
#ColumnID = 1
, #Value = 6
, #TableName = 'dbo.bb_match'
SELECT #SQL = 'SELECT * FROM ' + #TableName + ' WHERE [' + c.name + '] = ' + CAST(#Value AS NVARCHAR(MAX))
FROM sys.objects o WITH (NOWAIT)
JOIN sys.schemas s WITH (NOWAIT) ON o.[schema_id] = s.[schema_id]
JOIN sys.columns c WITH (NOWAIT) ON o.[object_id] = c.[object_id]
WHERE o.[type] = 'U' -- <-- only for tables columns
AND s.name + '.' + o.name = #TableName
AND c.column_id = #ColumnID
PRINT #SQL
EXEC sp_executesql #SQL
Shorter, but unsafe (sys.columns contains column_name for tables, views, procedures, ...):
SELECT #SQL = 'SELECT * FROM ' + #TableName + ' WHERE [' + c.name + '] = ' + CAST(#Value AS NVARCHAR(MAX))
FROM sys.columns c WITH (NOWAIT)
WHERE c.[object_id] = OBJECT_ID(#TableName)
AND c.column_id = #ColumnID
EXEC sys.sp_executesql #SQL
Output:
SELECT * FROM dbo.bb_match WHERE [seek_id] = 6
Results:
seek_id prov_id
----------- -----------
6 1
declare #sql varchar(MAX)
declare #tablename varchar(100) = 'MyTable' --add your table name here
declare #value varchar(100) = 'SomeValue' -- add your desired value hree
select #sql = 'SELECT * FROM ' + #tablename + ' WHERE '
+ name
+ ' = ''' + #value + ''''
from sys.columns where object_id = object_id(#tablename) and column_id = 1
exec (#sql)
There are three parts to this. First I'm declaring three strings. #sql is where I will build up the query, #tablename and #value are the table and search value to look in/for. I've put in the dummy values MyTable and SomeValue to show what I'm talking about
Next I build up the sql statement. The first line sets the string as SELECT * FROM MyTable WHERE
I then add in the column name by selecting Name from the SQL SERver system table sys.columns, filtering on the first column (column_id = 1) and the table name
The next step is to add the value we want to search for in the column.
Finally, EXEC(#sql) interprets the string as a command and runs it.
I want to be able to insert data from a table with an identity column into a temporary table in SQL Server 2005.
The TSQL looks something like:
-- Create empty temp table
SELECT *
INTO #Tmp_MyTable
FROM MyTable
WHERE 1=0
...
WHILE ...
BEGIN
...
INSERT INTO #Tmp_MyTable
SELECT TOP (#n) *
FROM MyTable
...
END
The above code created #Tmp_Table with an identity column, and the insert subsequently fails with an error "An explicit value for the identity column in table '#Tmp_MyTable' can only be specified when a column list is used and IDENTITY_INSERT is ON."
Is there a way in TSQL to drop the identity property of the column in the temporary table without listing all the columns explicitly? I specifically want to use "SELECT *" so that the code will continue to work if new columns are added to MyTable.
I believe dropping and recreating the column will change its position, making it impossible to use SELECT *.
Update:
I've tried using IDENTITY_INSERT as suggested in one response. It's not working - see the repro below. What am I doing wrong?
-- Create test table
CREATE TABLE [dbo].[TestTable](
[ID] [numeric](18, 0) IDENTITY(1,1) NOT NULL,
[Name] [varchar](50) NULL,
CONSTRAINT [PK_TestTable] PRIMARY KEY CLUSTERED
(
[ID] ASC
)
)
GO
-- Insert some data
INSERT INTO TestTable
(Name)
SELECT 'One'
UNION ALL
SELECT 'Two'
UNION ALL
SELECT 'Three'
GO
-- Create empty temp table
SELECT *
INTO #Tmp
FROM TestTable
WHERE 1=0
SET IDENTITY_INSERT #Tmp ON -- I also tried OFF / ON
INSERT INTO #Tmp
SELECT TOP 1 * FROM TestTable
SET IDENTITY_INSERT #Tmp OFF
GO
-- Drop test table
DROP TABLE [dbo].[TestTable]
GO
Note that the error message "An explicit value for the identity column in table '#TmpMyTable' can only be specified when a column list is used and IDENTITY_INSERT is ON." - I specifically don't want to use a column list as explained above.
Update 2
Tried the suggestion from Mike but this gave the same error:
-- Create empty temp table
SELECT *
INTO #Tmp
FROM (SELECT
m1.*
FROM TestTable m1
LEFT OUTER JOIN TestTable m2 ON m1.ID=m2.ID
WHERE 1=0
) dt
INSERT INTO #Tmp
SELECT TOP 1 * FROM TestTable
As for why I want to do this: MyTable is a staging table which can contain a large number of rows to be merged into another table. I want to process the rows from the staging table, insert/update my main table, and delete them from the staging table in a loop that processes N rows per transaction. I realize there are other ways to achieve this.
Update 3
I couldn't get Mike's solution to work, however it suggested the following solution which does work: prefix with a non-identity column and drop the identity column:
SELECT CAST(1 AS NUMERIC(18,0)) AS ID2, *
INTO #Tmp
FROM TestTable
WHERE 1=0
ALTER TABLE #Tmp DROP COLUMN ID
INSERT INTO #Tmp
SELECT TOP 1 * FROM TestTable
Mike's suggestion to store only the keys in the temporary table is also a good one, though in this specific case there are reasons I prefer to have all columns in the temporary table.
You could try
SET IDENTITY_INSERT #Tmp_MyTable ON
-- ... do stuff
SET IDENTITY_INSERT #Tmp_MyTable OFF
This will allow you to select into #Tmp_MyTable even though it has an identity column.
But this will not work:
-- Create empty temp table
SELECT *
INTO #Tmp_MyTable
FROM MyTable
WHERE 1=0
...
WHILE ...
BEGIN
...
SET IDENTITY_INSERT #Tmp_MyTable ON
INSERT INTO #Tmp_MyTable
SELECT TOP (#n) *
FROM MyTable
SET IDENTITY_INSERT #Tmp_MyTable OFF
...
END
(results in the error "An explicit value for the identity column in table '#Tmp' can only be specified when a column list is used and IDENTITY_INSERT is ON.")
It seems there is no way without actually dropping the column - but that would change the order of columns as OP mentioned. Ugly hack: Create a new table based on #Tmp_MyTable ...
I suggest you write a stored procedure that creates a temporary table based on a table name (MyTable) with the same columns (in order), but with the identity property missing.
You could use following code:
select t.name as tablename, typ.name as typename, c.*
from sys.columns c inner join
sys.tables t on c.object_id = t.[object_id] inner join
sys.types typ on c.system_type_id = typ.system_type_id
order by t.name, c.column_id
to get a glimpse on how reflection works in TSQL. I believe you will have to loop over the columns for the table in question and execute dynamic (hand-crafted, stored in strings and then evaluated) alter statements to the generated table.
Would you mind posting such a stored procedure for the rest of the world? This question seems to come up quite a lot in other forums as well...
IF you are just processing rows as you describe, wouldn't it be better to just select the top N primary key values into a temp table like:
CREATE TABLE #KeysToProcess
(
TempID int not null primary key identity(1,1)
,YourKey1 int not null
,YourKey2 int not null
)
INSERT INTO #KeysToProcess (YourKey1,YourKey2)
SELECT TOP n YourKey1,YourKey2 FROM MyTable
The keys should not change very often (I hope) but other columns can with no harm to doing it this way.
get the ##ROWCOUNT of the insert and you can do a easy loop on TempID where it will be from 1 to ##ROWCOUNT
and/or
just join #KeysToProcess to your MyKeys table and be on your way, with no need to duplicate all the data.
This runs fine on my SQL Server 2005, where MyTable.MyKey is an identity column.
-- Create empty temp table
SELECT *
INTO #TmpMikeMike
FROM (SELECT
m1.*
FROM MyTable m1
LEFT OUTER JOIN MyTable m2 ON m1.MyKey=m2.MyKey
WHERE 1=0
) dt
INSERT INTO #TmpMike
SELECT TOP 1 * FROM MyTable
SELECT * from #TmpMike
EDIT
THIS WORKS, with no errors...
-- Create empty temp table
SELECT *
INTO #Tmp_MyTable
FROM (SELECT
m1.*
FROM MyTable m1
LEFT OUTER JOIN MyTable m2 ON m1.KeyValue=m2.KeyValue
WHERE 1=0
) dt
...
WHILE ...
BEGIN
...
INSERT INTO #Tmp_MyTable
SELECT TOP (#n) *
FROM MyTable
...
END
however, what is your real problem? Why do you need to loop while inserting "*" into this temp table? You may be able to shift strategy and come up with a much better algorithm overall.
EDIT Toggling IDENTITY_INSERT as suggested by Daren is certainly the more elegant approach, in my case I needed to eliminate the identity column so that I could reinsert selected data into the source table
The way that I addressed this was to create the temp table just as you do, explicitly drop the identity column, and then dynamically build the sql so that I have a column list that excludes the identity column (as in your case so the proc would still work if there were changes to the schema) and then execute the sql here's a sample
declare #ret int
Select * into #sometemp from sometable
Where
id = #SomeVariable
Alter Table #sometemp Drop column SomeIdentity
Select #SelectList = ''
Select #SelectList = #SelectList
+ Coalesce( '[' + Column_name + ']' + ', ' ,'')
from information_schema.columns
where table_name = 'sometable'
and Column_Name <> 'SomeIdentity'
Set #SelectList = 'Insert into sometable ('
+ Left(#SelectList, Len(#SelectList) -1) + ')'
Set #SelectList = #SelectList
+ ' Select * from #sometemp '
exec #ret = sp_executesql #selectlist
I have wrote this procedure as compilation of many answers to automatically and fast drop column identity:
CREATE PROCEDURE dbo.sp_drop_table_identity #tableName VARCHAR(256) AS
BEGIN
DECLARE #sql VARCHAR (4096);
DECLARE #sqlTableConstraints VARCHAR (4096);
DECLARE #tmpTableName VARCHAR(256) = #tableName + '_noident_temp';
BEGIN TRANSACTION
-- 1) Create temporary table with edentical structure except identity
-- Idea borrowed from https://stackoverflow.com/questions/21547/in-sql-server-how-do-i-generate-a-create-table-statement-for-a-given-table
-- modified to ommit Identity and honor all constraints, not primary key only!
SELECT
#sql = 'CREATE TABLE [' + so.name + '_noident_temp] (' + o.list + ')'
+ ' ' + j.list
FROM sysobjects so
CROSS APPLY (
SELECT
' [' + column_name + '] '
+ data_type
+ CASE data_type
WHEN 'sql_variant' THEN ''
WHEN 'text' THEN ''
WHEN 'ntext' THEN ''
WHEN 'xml' THEN ''
WHEN 'decimal' THEN '(' + CAST(numeric_precision as VARCHAR) + ', ' + CAST(numeric_scale as VARCHAR) + ')'
ELSE COALESCE('(' + CASE WHEN character_maximum_length = -1 THEN 'MAX' ELSE CAST(character_maximum_length as VARCHAR) END + ')', '')
END
+ ' '
/* + case when exists ( -- Identity skip
select id from syscolumns
where object_name(id)=so.name
and name=column_name
and columnproperty(id,name,'IsIdentity') = 1
) then
'IDENTITY(' +
cast(ident_seed(so.name) as varchar) + ',' +
cast(ident_incr(so.name) as varchar) + ')'
else ''
end + ' ' */
+ CASE WHEN IS_NULLABLE = 'No' THEN 'NOT ' ELSE '' END
+ 'NULL'
+ CASE WHEN information_schema.columns.column_default IS NOT NULL THEN ' DEFAULT ' + information_schema.columns.column_default ELSE '' END
+ ','
FROM
INFORMATION_SCHEMA.COLUMNS
WHERE table_name = so.name
ORDER BY ordinal_position
FOR XML PATH('')
) o (list)
CROSS APPLY(
SELECT
CHAR(10) + 'ALTER TABLE ' + #tableName + '_noident_temp ADD ' + LEFT(alt, LEN(alt)-1)
FROM(
SELECT
CHAR(10)
+ ' CONSTRAINT ' + tc.constraint_name + '_ni ' + tc.constraint_type + ' (' + LEFT(c.list, LEN(c.list)-1) + ')'
+ COALESCE(CHAR(10) + r.list, ', ')
FROM
information_schema.table_constraints tc
CROSS APPLY(
SELECT
'[' + kcu.column_name + '], '
FROM
information_schema.key_column_usage kcu
WHERE
kcu.constraint_name = tc.constraint_name
ORDER BY
kcu.ordinal_position
FOR XML PATH('')
) c (list)
OUTER APPLY(
-- https://stackoverflow.com/questions/3907879/sql-server-howto-get-foreign-key-reference-from-information-schema
SELECT
' REFERENCES [' + kcu1.constraint_schema + '].' + '[' + kcu2.table_name + ']' + '([' + kcu2.column_name + ']) '
+ CHAR(10)
+ ' ON DELETE ' + rc.delete_rule
+ CHAR(10)
+ ' ON UPDATE ' + rc.update_rule + ', '
FROM information_schema.referential_constraints as rc
JOIN information_schema.key_column_usage as kcu1 ON (kcu1.constraint_catalog = rc.constraint_catalog AND kcu1.constraint_schema = rc.constraint_schema AND kcu1.constraint_name = rc.constraint_name)
JOIN information_schema.key_column_usage as kcu2 ON (kcu2.constraint_catalog = rc.unique_constraint_catalog AND kcu2.constraint_schema = rc.unique_constraint_schema AND kcu2.constraint_name = rc.unique_constraint_name AND kcu2.ordinal_position = KCU1.ordinal_position)
WHERE
kcu1.constraint_catalog = tc.constraint_catalog AND kcu1.constraint_schema = tc.constraint_schema AND kcu1.constraint_name = tc.constraint_name
) r (list)
WHERE tc.table_name = #tableName
FOR XML PATH('')
) a (alt)
) j (list)
WHERE
xtype = 'U'
AND name NOT IN ('dtproperties')
AND so.name = #tableName
SELECT #sql as '1) #sql';
EXECUTE(#sql);
-- 2) Obtain current back references on our table from others to reenable it later
-- https://stackoverflow.com/questions/3907879/sql-server-howto-get-foreign-key-reference-from-information-schema
SELECT
#sqlTableConstraints = (
SELECT
'ALTER TABLE [' + kcu1.constraint_schema + '].' + '[' + kcu1.table_name + ']'
+ ' ADD CONSTRAINT ' + kcu1.constraint_name + '_ni FOREIGN KEY ([' + kcu1.column_name + '])'
+ CHAR(10)
+ ' REFERENCES [' + kcu2.table_schema + '].[' + kcu2.table_name + ']([' + kcu2.column_name + '])'
+ CHAR(10)
+ ' ON DELETE ' + rc.delete_rule
+ CHAR(10)
+ ' ON UPDATE ' + rc.update_rule + ' '
FROM information_schema.referential_constraints as rc
JOIN information_schema.key_column_usage as kcu1 ON (kcu1.constraint_catalog = rc.constraint_catalog AND kcu1.constraint_schema = rc.constraint_schema AND kcu1.constraint_name = rc.constraint_name)
JOIN information_schema.key_column_usage as kcu2 ON (kcu2.constraint_catalog = rc.unique_constraint_catalog AND kcu2.constraint_schema = rc.unique_constraint_schema AND kcu2.constraint_name = rc.unique_constraint_name AND kcu2.ordinal_position = KCU1.ordinal_position)
WHERE
kcu2.table_name = 'department'
FOR XML PATH('')
);
SELECT #sqlTableConstraints as '8) #sqlTableConstraints';
-- Execute at end
-- 3) Drop outer references for switch (structure must be identical: http://msdn.microsoft.com/en-gb/library/ms191160.aspx) and rename table
SELECT
#sql = (
SELECT
' ALTER TABLE [' + kcu1.constraint_schema + '].' + '[' + kcu1.table_name + '] DROP CONSTRAINT ' + kcu1.constraint_name
FROM information_schema.referential_constraints as rc
JOIN information_schema.key_column_usage as kcu1 ON (kcu1.constraint_catalog = rc.constraint_catalog AND kcu1.constraint_schema = rc.constraint_schema AND kcu1.constraint_name = rc.constraint_name)
JOIN information_schema.key_column_usage as kcu2 ON (kcu2.constraint_catalog = rc.unique_constraint_catalog AND kcu2.constraint_schema = rc.unique_constraint_schema AND kcu2.constraint_name = rc.unique_constraint_name AND kcu2.ordinal_position = KCU1.ordinal_position)
WHERE
kcu2.table_name = #tableName
FOR XML PATH('')
);
SELECT #sql as '3) #sql'
EXECUTE (#sql);
-- 4) Switch partition
-- http://www.calsql.com/2012/05/removing-identity-property-taking-more.html
SET #sql = 'ALTER TABLE ' + #tableName + ' switch partition 1 to ' + #tmpTableName;
SELECT #sql as '4) #sql';
EXECUTE(#sql);
-- 5) Rename real old table to bak
SET #sql = 'EXEC sp_rename ' + #tableName + ', ' + #tableName + '_bak';
SELECT #sql as '5) #sql';
EXECUTE(#sql);
-- 6) Rename temp table to real
SET #sql = 'EXEC sp_rename ' + #tmpTableName + ', ' + #tableName;
SELECT #sql as '6) #sql';
EXECUTE(#sql);
-- 7) Drop bak table
SET #sql = 'DROP TABLE ' + #tableName + '_bak';
SELECT #sql as '7) #sql';
EXECUTE(#sql);
-- 8) Create again doped early constraints
SELECT #sqlTableConstraints as '8) #sqlTableConstraints';
EXECUTE(#sqlTableConstraints);
-- It still may fail if there references from objects with WITH CHECKOPTION
-- it may be recreated - https://stackoverflow.com/questions/1540988/sql-2005-force-table-rename-that-has-dependencies
COMMIT
END
Use is pretty simple:
EXEC sp_drop_table_identity #tableName = 'some_very_big_table'
Benefits and limitations:
It uses switch partition (applicable to not partitioned tables too) statement for fast move without full data copy. It also apply some conditions for applicability.
It make on the fly table copy without identity. Such solution I also post separately and it also may need tuning on not so trivial structures like compound fields (it cover my needs).
If table included in objects with schema bound by CHECKOUPTION (sp, views) it prevent do switching (see last comment in code). It may be additionally scripted to temporary drop such binding. I had not do that yet.
All feedback welcome.
Most efficient way to drop identity columns (especially for large databases) on SQL Server is to modify DDL metadata directly, on SQL Server older than 2005 this can be done with:
sp_configure 'allow update', 1
go
reconfigure with override
go
update syscolumns set colstat = 0 --turn off bit 1 which indicates identity column
where id = object_id('table_name') and name = 'column_name'
go
exec sp_configure 'allow update', 0
go
reconfigure with override
go
SQL Server 2005+ doesn't support reconfigure with override, but you can execute Ad Hoc Queries when SQL Server instance is started in single-user mode (start db instance with -m flag, i.e. "C:\Program Files\Microsoft SQL Server\MSSQL10.MSSQLSERVER\MSSQL\Binn\sqlservr.exe -m", make sure to run as Administrator) with Dedicated Admin Console (from SQL Management Studio connect with ADMIN: prefix, i.e. ADMIN:MyDatabase). Column metdata is stored in sys.sysschobjs internal table (not shown without DAC):
use myDatabase
update sys.syscolpars set status = 1, idtval = null -- status=1 - primary key, idtval=null - remove identity data
where id = object_id('table_name') AND name = 'column_name'
More on this approach on this blog