How to drop a SQL Server constraint when you don’t know its name
If you are looking after a database that has been haphazardly maintained in the past, you might come across inconsistent naming of things such as constraints. When you come to delete the existing one, it might be tricky if it doesn’t have the same name across environments.
That’s when you need to do a lookup to get the name, so you can drop the constraint. You can use this to target constraints by column and table names. In the future, never let anyone except a human name your constraints.
DECLARE @constraint NVARCHAR(200), @command NVARCHAR(300) SELECT @constraint = default_constraints.name FROM sys.all_columns INNER JOIN sys.tables ON all_columns.object_id = tables.object_id INNER JOIN sys.schemas ON tables.schema_id = schemas.schema_id INNER JOIN sys.default_constraints ON all_columns.default_object_id = default_constraints.object_id WHERE schemas.name = 'dbo' AND tables.name = 'MyTableName' AND all_columns.name = 'MyFieldName' IF @constraint IS NOT NULL BEGIN SELECT @command = 'ALTER TABLE MyTableName DROP CONSTRAINT ' + @constraint; EXECUTE(@command) END GO