DROP CONSTRAINT

The DROP CONSTRAINT data description statement deletes the definition of a referential constraint from the dictionary. It is also a CA IDMS extension of the SQL standard.
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The DROP CONSTRAINT data description statement deletes the definition of a referential constraint from the dictionary. It is also a CA IDMS extension of the SQL standard.
Authorization
To issue a DROP CONSTRAINT statement, you must own or have the ALTER privilege on the referencing table in the constraint named in the statement.
Syntax
  ►►─── DROP CONSTRAINT 
constraint-name
 ────────────────────────────────────────►  ►─── FROM ──┬────────────────┬── 
table-identifier
 ───────────────────────────►◄              └─ 
schema-name
. ─┘  
Parameters
  • constraint-name
    Specifies the name of the referential constraint being dropped.
    Constraint-name
    must identify a referential constraint defined in the dictionary.
  • table-identifier
    Specifies the referencing table in the constraint to be dropped.
  • schema-name
    Identifies the schema with which the table is associated.
    If you do not specify a
    schema-name
    , the default value is:
    • The current schema associated with your SQL session, if the statement is entered through the Command Facility or executed dynamically
    • The schema associated with the access module used at runtime, if the statement is embedded in an application program
Usage
Referential Constraints Involving SYSTEM Tables
You cannot delete a constraint involving a table in the SYSTEM schema.
Implicitly Dropped Constraints
When you issue a DROP TABLE statement with the CASCADE parameter, CA IDMS deletes the definitions of all referential constraints in which the table being dropped is the referencing table or the referenced table.
Linked Constraints
When dropping a linked constraint, CA IDMS updates every row in the referenced and referencing tables to remove the physical links between the two tables.
Example
Dropping a Referential Constraint
The following DROP CONSTRAINT statement deletes the definition of the OFFICE_POOL_EMP constraint from the dictionary:
drop constraint office_pool_emp;
More Information
  • For more information about defining referential constraints, see CREATE CONSTRAINT.
  • For more information about implicitly dropping referential constraints, see DROP TABLE.