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Delete column having default constraint in SQL server


It's one of the common question while deleting column from a table. How we will delete a column having default constraint. If we try to delete a column having Default constraint, then it will raise error. 
Looking for Answer, here we go:

Declare two variables as:

DECLARE @ConstraintName NVARCHAR(200), @sql  NVARCHAR(MAX)

Now set the value of @ConstraintName as Default constraint name:

SET @ConstraintName = (SELECT NAME AS DEFAULT_CONSTRAINT_NAME
FROM SYS.DEFAULT_CONSTRAINTS
WHERE OBJECT_NAME(PARENT_OBJECT_ID) = '<Table_Name>')

After this create run-time query to delete constraint and set it to @sql:

SET @sql = N'ALTER TABLE <Table_Name> DROP CONSTRAINT ' + @ConstraintName

And with the help of sp_executesql drop the constraint as:

EXEC sp_executesql @sql

And as constraint is deleted so finally delete the column without any error.

ALTER TABLE <Table_Name> DROP COLUMN <Column_Name>

Here is complete script for copy paste champs..;)

DECLARE @ConstraintName NVARCHAR(200), @sql  NVARCHAR(MAX)
SET @ConstraintName = (SELECT NAME AS DEFAULT_CONSTRAINT_NAME
FROM SYS.DEFAULT_CONSTRAINTS
WHERE OBJECT_NAME(PARENT_OBJECT_ID) = '<Table_Name>')
SET @sql = N'ALTER TABLE <Table_Name> DROP CONSTRAINT ' + @ConstraintName
EXEC sp_executesql @sql
ALTER TABLE <Table_Name> DROP COLUMN <Column_Name>

Cheers friends...:)
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Comments

  1. sandyNovember 26, 2012 at 6:04 PM

    If a default constraint is applied on more then one column, then how can we make sure that only the required column's default constraint will get deleted.

    ReplyDelete

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