Enabling a Constraint : Constraint « Table « Oracle PL/SQL Tutorial

You can enable an existing constraint using the ENABLE CONSTRAINT clause of ALTER TABLE.
To enable a constraint, all the rows in the table must satisfy the constraint.

SQL> -- create demo table
SQL> create table myTable(
  2    id           NUMBER(2),
  3    value        NUMBER(6,2)
  4  )
  5  /

Table created.

SQL>
SQL>
SQL>
SQL> ALTER TABLE myTable
  2  ADD CONSTRAINT uq UNIQUE (id) DISABLE;

Table altered.

SQL>
SQL>
SQL> ALTER TABLE myTable
  2  DISABLE CONSTRAINT uq;

Table altered.

SQL>
SQL>
SQL> ALTER TABLE myTable
  2  ENABLE CONSTRAINT uq;

Table altered.

SQL>
SQL>
SQL> drop table myTable
  2  /

Table dropped.
SQL>

6.10.Constraint
	6.10.1.	Adding a Constraint
	6.10.2.	Add constaint for a date type column: larger than a certain date
	6.10.3.	Adding a 'NOT NULL' Constraint
	6.10.4.	The database automatically assigns a name to the constraint
	6.10.5.	Dropping a Constraint
	6.10.6.	Disabling a Constraint
	6.10.7.	Add CASCADE to the end of a DISABLE CONSTRAINT clause
	6.10.8.	Enabling a Constraint
	6.10.9.	You can also choose to apply a constraint to new data only by specifying ENABLE NOVALIDATE.
	6.10.10.	Deferred Constraints
	6.10.11.	How to drop a constaint
	6.10.12.	Violate a constraint
	6.10.13.	Cascade constraints