语句如下：

explain_stmt:
      explain_key table_name [column_name]
    | explain_key [explain_type] explainable_stmt
explain_key:
    {EXPLAIN | DESCRIBE | DESC}
explain_type:
      BASIC
    | OUTLINE
    | EXTENDED
    | EXTENDED_NOADDR
    | PLANREGRESS
    | PARTITIONS
    | FORMAT = {TRADITIONAL | JSON}
explainable_stmt:
      select_stmt
    | insert_stmt
    | update_stmt
    | delete_stmt
    | replace_stmt