variable_declaration ::=
variable_name datatype [ [ NOT NULL] {:= | DEFAULT} expression ] ;
datatype ::=
{ collection_name %TYPE
| collection_type_name
| cursor_name %ROWTYPE>
| cursor_variable_name %TYPE
| db_table_name { %ROWTYPE | .column_name %TYPE }
| object_name %TYPE
| [REF] object_type_name
| record_name %TYPE
| record_type_name
| ref_cursor_type_name
| scalar_datatype_name
| variable_name %TYPE
}