Msg 3717, Level 16, State 1, Line 1
Cannot drop a default constraint by DROP DEFAULT statement. Use ALTER TABLE to drop a constraint default.
This error message appears when you try to DROP a column-level DEFAULT constraint with a DROP DEFAULT statement.
The T-SQL statement can be parsed, but causes the error at runtime.
Error of the Severity Level 16 are generated by the user and can be fixed by the SQL Server user. You must use the ALTER TABLE statement to drop a column-level DEFAULT constraint.
This error message was introduced with SQL Server 2005.
CREATE TABLE t
c1 INT NOT NULL CONSTRAINT DF_c1 DEFAULT 0
DROP DEFAULT DF_c1
DROP TABLE t
There are two “types” of DEFAULTs. One, that are explictly created for a column of a table und one that are create on the database level via CREATE DEFAULT. You should refrain from using the CREATE/DROP DEFAULT statements. They will be removed in a future version of SQL Server.