| alter_table_statement::= ALTER TABLE [ IF EXISTS ] table_name alter_table_instruction |
| alter_table_instruction::= ADD [ IF NOT EXISTS ] column_definition ( ',' column_definition)* |
| | DROP [ IF EXISTS ] column_name ( ',' column_name )* |
| | RENAME [ IF EXISTS ] column_name to column_name (AND column_name to column_name)* |
| | ALTER [ IF EXISTS ] column_name ( column_mask | DROP MASKED ) |
| | WITH options |
| column_definition::= column_name cql_type [ column_mask] |
| column_mask::= MASKED WITH ( DEFAULT | function_name '(' term ( ',' term )* ')' ) |
