ApsaraDB for OceanBase:Modify, drop, and add constraints

Syntax

constraint_clauses:
{ ADD { { out_of_line_constraint }...
      | out_of_line_REF_constraint
      }
| MODIFY { CONSTRAINT constraint_name
         | PRIMARY KEY
         | UNIQUE (column [, column ]...)
         } constraint_state [ CASCADE ]
| RENAME CONSTRAINT old_name TO new_name
| { drop_constraint_clause }...
}

out_of_line_constraint:
[ CONSTRAINT constraint_name ]
{ UNIQUE (column [, column ]...)
| PRIMARY KEY (column [, column ]...)
| FOREIGN KEY (column [, column ]...) references_clause
| CHECK (condition)
} [ constraint_state ]

out_of_line_REF_constraint:
{ SCOPE FOR ({ ref_col | ref_attr })
    IS [ schema. ] scope_table
| REF ({ ref_col | ref_attr }) WITH ROWID
| [ CONSTRAINT constraint_name ] FOREIGN KEY
    ( { ref_col [, ref_col ] | ref_attr [, ref_attr ] } ) references_clause
    [ constraint_state ]
}

drop_constraint_clause:
(
  DROP ( ( PRIMARY KEY
         | UNIQUE "(" (column)... ")"  
         | CONSTRAINT constraint_name ) 
		 [ CASCADE ] [( KEEP | DROP ) INDEX ]
	   ) 
	   [ ONLINE ]
)

Supported operations

Dropping a constraint by specifying CONSTRAINT constraint_name in the drop_constraint_clause clause is supported. Only one constraint can be dropped at a time. Sample code:

ALTER TABLE T DROP CONSTRAINT CST;

Unsupported operations

• Dropping the primary key or unique key is not supported. An error will be returned when you perform this operation.

• Adding new constraints is not supported. An error will be returned when you perform this operation.

• Modifying constraints is not supported. An error will be returned when you perform this operation.

• Renaming constraints is not supported. An error will be returned when you perform this operation.

Ignored clauses and options

• The CASCADE clause.

• The KEEP | DROP INDEX clause for specifying whether to keep or drop indexes.

• The ONLINE option for allowing table DML operations when dropping a constraint.