MySQL 中编写一个 SQL 语句，将某一字段的值修改为与 id 字段的值相同

  1. UPDATE md_documents SET identify = CONCAT(document_id, '.html') WHERE
  2. document_id > 2270 ;
  4. UPDATE md_documents SET order_sort = document_id WHERE document_id > 2270 ;
  6. UPDATE md_documents SET is_free_read = 2 WHERE document_id > 2270 ;
  8. SELECT * FROM md_documents ORDER BY document_id DESC LIMIT 10;