You can delete table properties by specifying a DROP definition in the
ALTER TABLE statement.Syntax
<drop_definition> ::= DROP <column_name>,... [<cascade_option>] [RELEASE SPACE]
| DROP (<column_name>,...) [<cascade_option>] [RELEASE SPACE]
| DROP CONSTRAINT <constraint_name> | DROP PRIMARY KEY
Explanation
Dropping a column: DROP <column_name>
Each column name must be a column of the table identified by the ALTER TABLE statement. The column must be neither a key column nor a foreign key column of a
referential CONSTRAINT definition of the table.The columns are marked as dropped in the metadata of the table. A DROP definition does not automatically reduce the memory requirements of the underlying table.
RELEASE SPACE forces the column values of the dropped columns to be dropped in every row in the table. With large tables, in particular, this may take more time, since extensive copy operations have to be carried out.Any privileges and comments for the columns to be dropped are dropped as well.
If one of the columns to be dropped occurs as a
selected column in a view definition, the specified column in the view table is dropped.Existing indexes referring to columns to be dropped are also dropped. The storage locations for the dropped indexes are released.
All
CONSTRAINT definitions that contain one of the dropped columns are dropped.Dropping a constraint: DROP CONSTRAINT <constraint_name>
The constraint name must identify a CONSTRAINT definition in the table. The latter is then removed from the metadata of the table.
Dropping a key: DROP PRIMARY KEY
The key is replaced by the key column SYSKEY generated by the database system. With large tables, in particular, this may take more time, since extensive copy operations have to be carried out.