Dropping unique constraints in sql server
0 likes1,765 views
The document discusses how to drop unique constraints in SQL Server using a stored procedure that queries the data dictionary for unique constraints on a specified table and column. It outlines a method for executing the drop action while noting a limitation that only applies to single-column unique constraints. Feedback from SQL procedure experts is encouraged to improve the method's functionality.
![Generation 5 » Dropping Unique Constraints in SQL Server
Subscribe to our RSS Feed | About Us
Dropping Unique Constraints in SQL Server
Search for:
The problem
Search
I got started with relational databases with mysql, so I’m in the habit of making
database changes with SQL scripts, rather than using a GUI. Microsoft SQL Server
requires that we specify the name of a unique constraint when we want to drop it. If
you’re thinking ahead, you can specify a name when you create the constraint; if
you don’t, SQL Server will make up an unpredictable name, so you can’t write a
simple script to drop the constraint.
A Solution
In the spirit of “How To Drop A Primary Key in SQL Server“, here’s a stored
procedure that queries the data dictionary to find the names of any unique constraint
on a specific table and column and drop them:
CREATE PROCEDURE [dbo].[DropUniqueConstraint]
@tableName NVarchar(255),
@columnName NVarchar(255)
AS
DECLARE @IdxNames CURSOR
SET @IdxNames = CURSOR FOR
select sysindexes.name from sysindexkeys,syscolumns,sysindexes
WHERE
syscolumns.[id] = OBJECT_ID(N'[dbo].['+@tableName+N']')
AND sysindexkeys.[id] = OBJECT_ID(N'[dbo].['+@tableName+N']')
AND sysindexes.[id] = OBJECT_ID(N'[dbo].['+@tableName+N']')
AND syscolumns.name=@columnName
AND sysindexkeys.colid=syscolumns.colid
AND sysindexes.[indid]=sysindexkeys.[indid]
AND (
SELECT COUNT(*) FROM sysindexkeys AS si2
WHERE si2.id=sysindexes.id
AND si2.indid=sysindexes.indid
)=1
OPEN @IdxNames
DECLARE @IdxName Nvarchar(255)
FETCH NEXT FROM @IdxNames INTO @IdxName
WHILE @@FETCH_STATUS = 0 BEGIN
DECLARE @dropSql Nvarchar(4000)
SET @dropSql=
N'ALTER TABLE ['+@tableName+ N']
DROP CONSTRAINT ['+@IdxName+ N']'
EXEC(@dropSql)
FETCH NEXT FROM @IdxNames
INTO @IdxName
END
CLOSE @IdxNames
DEALLOCATE @IdxNames
Usage is straightforward:
EXEC [dbo].[DropUniqueConstraint]
@tableName='TargetTable',
@columnName='TargetColumn'
This script has a limitation: it only drops unique constraints that act on a single
column, not constraints that act on multiple columns. It is smart enough, however,
to not drop multiple-column constraints in case one of them involves @columnName .
Feedback from SQL stored procedure wizards would be mostly certainly welcome.
Paul Houle on June 26th 2008 in SQL
Comments
http://gen5.info/q/2008/06/26/dropping-unique-constraints-in-sql-server/[1/16/2014 3:58:30 PM]
Comments (0)
Login
Archives
June 2012 (1)
August 2010 (1)
May 2010 (1)
June 2009 (2)
April 2009 (1)
March 2009 (1)
February 2009 (3)
January 2009 (3)
November 2008 (1)
August 2008 (2)
July 2008 (5)
June 2008 (5)
May 2008 (2)
April 2008 (6)
March 2008 (8)
June 2006 (1)
February 2006 (1)
Categories
AJAX (2)
Asynchronous Communications (16)
Biology (1)
Books (1)
Design (1)
Distributed (1)
Exceptions (2)
Functional Programming (1)
GIS (1)
Ithaca (1)
Japan (1)
Math (1)
Media (3)
Nature (1)
Semantic Web (3)
Tools (28)
CRUD (1)
Dot Net (17)
Freebase (2)
GWT (9)
Java (7)
Linq (2)
PHP (6)
Server Frameworks (1)
Silverlight (12)
SQL (5)
Uncategorized (1)
Web (2)
Analytics (1)](https://image.slidesharecdn.com/droppinguniqueconstraintsinsqlserver-140116145941-phpapp02/85/Dropping-unique-constraints-in-sql-server-1-320.jpg)
![Generation 5 » Dropping Unique Constraints in SQL Server
There are no comments posted yet. Be the first one!
Post a new comment
Enter text right here!
Comment as a Guest, or login:
Name
Email
Website (optional)
Displayed next to your comments.
Not displayed publicly.
If you have a website, link to it here.
None
Subscribe to None
Submit Comment
Copyright © 2013 Generation 5.
WordPress Theme design.
http://gen5.info/q/2008/06/26/dropping-unique-constraints-in-sql-server/[1/16/2014 3:58:30 PM]](https://image.slidesharecdn.com/droppinguniqueconstraintsinsqlserver-140116145941-phpapp02/85/Dropping-unique-constraints-in-sql-server-2-320.jpg)
Dropping unique constraints in sql server
- 1. Generation 5 » Dropping Unique Constraints in SQL Server Subscribe to our RSS Feed | About Us Dropping Unique Constraints in SQL Server Search for: The problem Search I got started with relational databases with mysql, so I’m in the habit of making database changes with SQL scripts, rather than using a GUI. Microsoft SQL Server requires that we specify the name of a unique constraint when we want to drop it. If you’re thinking ahead, you can specify a name when you create the constraint; if you don’t, SQL Server will make up an unpredictable name, so you can’t write a simple script to drop the constraint. A Solution In the spirit of “How To Drop A Primary Key in SQL Server“, here’s a stored procedure that queries the data dictionary to find the names of any unique constraint on a specific table and column and drop them: CREATE PROCEDURE [dbo].[DropUniqueConstraint] @tableName NVarchar(255), @columnName NVarchar(255) AS DECLARE @IdxNames CURSOR SET @IdxNames = CURSOR FOR select sysindexes.name from sysindexkeys,syscolumns,sysindexes WHERE syscolumns.[id] = OBJECT_ID(N'[dbo].['+@tableName+N']') AND sysindexkeys.[id] = OBJECT_ID(N'[dbo].['+@tableName+N']') AND sysindexes.[id] = OBJECT_ID(N'[dbo].['+@tableName+N']') AND syscolumns.name=@columnName AND sysindexkeys.colid=syscolumns.colid AND sysindexes.[indid]=sysindexkeys.[indid] AND ( SELECT COUNT(*) FROM sysindexkeys AS si2 WHERE si2.id=sysindexes.id AND si2.indid=sysindexes.indid )=1 OPEN @IdxNames DECLARE @IdxName Nvarchar(255) FETCH NEXT FROM @IdxNames INTO @IdxName WHILE @@FETCH_STATUS = 0 BEGIN DECLARE @dropSql Nvarchar(4000) SET @dropSql= N'ALTER TABLE ['+@tableName+ N'] DROP CONSTRAINT ['+@IdxName+ N']' EXEC(@dropSql) FETCH NEXT FROM @IdxNames INTO @IdxName END CLOSE @IdxNames DEALLOCATE @IdxNames Usage is straightforward: EXEC [dbo].[DropUniqueConstraint] @tableName='TargetTable', @columnName='TargetColumn' This script has a limitation: it only drops unique constraints that act on a single column, not constraints that act on multiple columns. It is smart enough, however, to not drop multiple-column constraints in case one of them involves @columnName . Feedback from SQL stored procedure wizards would be mostly certainly welcome. Paul Houle on June 26th 2008 in SQL Comments http://gen5.info/q/2008/06/26/dropping-unique-constraints-in-sql-server/[1/16/2014 3:58:30 PM] Comments (0) Login Archives June 2012 (1) August 2010 (1) May 2010 (1) June 2009 (2) April 2009 (1) March 2009 (1) February 2009 (3) January 2009 (3) November 2008 (1) August 2008 (2) July 2008 (5) June 2008 (5) May 2008 (2) April 2008 (6) March 2008 (8) June 2006 (1) February 2006 (1) Categories AJAX (2) Asynchronous Communications (16) Biology (1) Books (1) Design (1) Distributed (1) Exceptions (2) Functional Programming (1) GIS (1) Ithaca (1) Japan (1) Math (1) Media (3) Nature (1) Semantic Web (3) Tools (28) CRUD (1) Dot Net (17) Freebase (2) GWT (9) Java (7) Linq (2) PHP (6) Server Frameworks (1) Silverlight (12) SQL (5) Uncategorized (1) Web (2) Analytics (1)
- 2. Generation 5 » Dropping Unique Constraints in SQL Server There are no comments posted yet. Be the first one! Post a new comment Enter text right here! Comment as a Guest, or login: Name Email Website (optional) Displayed next to your comments. Not displayed publicly. If you have a website, link to it here. None Subscribe to None Submit Comment Copyright © 2013 Generation 5. WordPress Theme design. http://gen5.info/q/2008/06/26/dropping-unique-constraints-in-sql-server/[1/16/2014 3:58:30 PM]