An Oracle PL/SQL constraint is a rule that must be followed by the data in a database table. PL/SQL constraints can be used to enforce data integrity, prevent duplicate data, and ensure that data is valid.
Benefits of using PL/SQL constraints on a table include:
– Enforcing data integrity
– Preventing duplicate data
– Ensuring that data is valid
PL/SQL constraints can be added to a table in Oracle database using the following commands:
add primary key to a table, add constraint foreign key, drop constraint, enable and disable a foreign key.
Add primary key
ALTER TABLE table_name ADD CONSTRAINT constraint_name PRIMARY KEY (column_name);
Example how to Add primary key
Add foreign key
ALTER TABLE table_name ADD CONSTRAINT constraint_name FOREIGN KEY (column_name) REFERENCES table_name (column_name);
Example how to Add constraint foreign key
ALTER TABLE table_name DROP CONSTRAINT constraint_name;
Example how to Drop constraint key
Enable a foreign key
ALTER TABLE table_name ENABLE CONSTRAINT constraint_name;
Example how to Enable a foreign key
Disable a foreign key
ALTER TABLE table_name DISABLE CONSTRAINT constraint_name;
Example how to Disable a foreign key
Constraints can also be used to check multiple conditions. For example, a unique constraint can be used to ensure that no two rows in a table have the same values for a certain column.
Oracle PL/SQL constraints are an important part of ensuring data integrity in a database. By using constraints, you can prevent duplicate data, ensure data is valid, and enforce data integrity.