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Now Dropping the Not Null constraints SQL> alter table emp drop constraint SYS_C00541121 Drop Not null or check constraints SQL> desc emp If you omit CASCADE, then Oracle Database does not drop the primary key or unique constraint if any foreign key references it. To drop the referenced key and the foreign key together, use the CASCADE clause. You cannot drop a primary key or unique key constraint that is part of a referential integrity constraint without also dropping the foreign key. We just need to first find all the constraints on the table and then drop them according to the need. We can drop primary key constraint, unique key constraint, foreign key constraint, check constraint and non null constraint using the same command given above. Here we have created two tables and created constraints for primary key, foreign key ,check constraint.Now that we have created the constraints,lets see how we can drop the constraint in oracleĭrop the constraint can be simply done by alter table drop constraint
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New 1: select CONSTRAINT_NAME,INDEX_NAME,CONSTRAINT_TYPE from user_constraints where TABLE_NAME='EMP' Old 1: select CONSTRAINT_NAME,INDEX_NAME,CONSTRAINT_TYPE from user_constraints where TABLE_NAME='&1' SQL> select CONSTRAINT_NAME,INDEX_NAME,CONSTRAINT_TYPE from user_constraints where TABLE_NAME='&1' Oracle Table creation and Constraint creation SQL> CREATE TABLE "DEPT"ĬONSTRAINT "PK_DEPT" PRIMARY KEY ("DEPTNO")ĬONSTRAINT "PK_EMP" PRIMARY KEY ("EMPNO"),ĬONSTRAINT "FK_DEPTNO" FOREIGN KEY ("DEPTNO") Lets check with the addition of constraint and then dropping them If we dont require constraint at any point of time, we can drop constraint in Oracle using the alter table command. Constraints are the ways to enforce data integrity rules in the Oracle database.