DROP CONSTRAINT ConstraintName;
-- removing CHECK constraint named amountCK
ALTER TABLE Orders
DROP CONSTRAINT amountCK;
/*To Drop Check Constraint*/
ALTER TABLE (Table_Name)
DROP CONSTRAINT (Constraint_Name)
ALTER TABLE (TABLE_NAME)
DROP CONSTRAINT (TABLENAME)_(COLUMNNAME)_CK;
ALTER TABLE TABLENAME
DROP CONSTRAINT TBNAME_COLNAME_CK;