1DECLARE @tableName VARCHAR(MAX) = '<MYTABLENAME>'
2DECLARE @columnName VARCHAR(MAX) = '<MYCOLUMNAME>'
3DECLARE @ConstraintName nvarchar(200)
4SELECT @ConstraintName = Name
5FROM SYS.DEFAULT_CONSTRAINTS
6WHERE PARENT_OBJECT_ID = OBJECT_ID(@tableName)
7AND PARENT_COLUMN_ID = (
8 SELECT column_id FROM sys.columns
9 WHERE NAME = @columnName AND object_id = OBJECT_ID(@tableName))
10IF @ConstraintName IS NOT NULL
11 EXEC('ALTER TABLE '+@tableName+' DROP CONSTRAINT ' + @ConstraintName)
12
13-- Just replace <MYTABLENAME> and <MYCOLUMNNAME>