How to disable primary key constraint of an existing table?

Oracle database constraints include but not limited to :

• Primary key
• Foreign key
• Unique key
• NOT NULL
• Check

on oracle, it is possible to disable constraints without re-creating and dropping them.

Here below is an example on how to add primary key constraints to an existing database table.

Example:

SQL> desc emp_sal;
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 EMP_ID                                             NUMBER
 SALARY                                             NUMBER
 JOBTITLE                                           VARCHAR2(12)
 SQL> alter table emp_sal add constraint pk_impID PRIMARY KEY(EMP_ID);
 Table altered.
 SQL>

Here is also an example on how to disable primary key constraint to an existing table.

SQL> alter table emp_sal disable constraint pk_impid;
 Table altered.
 SQL>

We can also enable primary key constraint of existing table using the below SQL command:

SQL> alter table emp_sal enable constraint pk_impid;
 Table altered.
 SQL>