An ALTER TABLE statement changes the properties of a base table (see Table).
<alter_table_statement>
::=
ALTER TABLE <table_name> <add_definition>
| ALTER TABLE <table_name> <drop_definition>
| ALTER TABLE <table_name> <alter_definition>
| ALTER TABLE <table_name> <column_change_definition>
| ALTER TABLE <table_name> <modify_definition>
| ALTER TABLE <table_name>
<referential_constraint_definition>
| ALTER TABLE <table_name> DROP FOREIGN KEY
<referential_constraint_name>
| ALTER TABLE <table_name>
<sample_definition>
table_name, add_definition, drop_definition, alter_definition, column_change_definition, modify_definition, referential_constraint_definition, referential_constraint_name, sample_definition
The table name must be the name of an existing base table. The table must not be a temporary base table. The current user must have the ALTER privilege for the specified table.
· If a referential CONSTRAINT definition was specified, a new referential constraint is defined for the base table. The rules described in the referential CONSTRAINT definition apply.
· If DROP FOREIGN KEY was specified, the referential CONSTRAINT definition identified by the name of the referential constraint is dropped.
· If a SAMPLE definition is specified, a new number of rows is defined and is taken into account by the database system when the table statistics are calculated.