DROP
- PRIMARY KEY
- Drops the definition of the primary key and all referential constraints
in which the primary key is a parent key. The table must have a primary key.
- FOREIGN KEY constraint-name
- Drops the referential constraint constraint-name. The constraint-name must identify a referential constraint in which the table
is a dependent.
- UNIQUE constraint-name
- Drops the unique constraint constraint-name and
all referential constraints dependent on this unique constraint. The constraint-name must identify a unique constraint on the table. DROP
UNIQUE will not drop a PRIMARY KEY unique constraint.
- CHECK constraint-name
- Drops the check constraint constraint-name.
The constraint-name must identify a check constraint
on the table.
- CONSTRAINT constraint-name
- Drops the constraint constraint-name. The constraint-name must identify a unique, referential, or check constraint on the table.
If the constraint is a PRIMARY KEY or UNIQUE constraint, all referential constraints
in which the primary key or unique key is a parent are also dropped.
- CASCADE
- Specifies for unique constraints that any referential constraints that
are dependent on the constraint being dropped are also dropped.
- RESTRICT
- Specifies for unique constraints that the constraint cannot be dropped
if any referential constraints are dependent on the constraint.
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