MySql动态生成SQL并执行

场景：由于一些表中设计了一些冗余字段，因此在主表修改了该冗余字段的值得时候，需要动态更新在其他表中冗余字段的值

BEGIN
    #Routine body goes here...
   
  /*SQL语句变量*/
  DECLARE vstrSql VARCHAR(3000) DEFAULT ''; 
  /*映射表字段*/
  DECLARE vSourceTableName VARCHAR(50);
  DECLARE vSourceIdFieldName VARCHAR(50);
  DECLARE vSourceNameFieldName VARCHAR(50);
  DECLARE vTargetTableName VARCHAR(50);
  DECLARE vTargetIdFieldName VARCHAR(50);
  DECLARE vTargetNameFieldName VARCHAR(50); 

  /*更新数据*/
  DECLARE vnewValue VARCHAR(100);
  DECLARE vSourceIdFieldValue VARCHAR(100);

  DECLARE Done INT DEFAULT 0;
  /*声明游标*/
  DECLARE curRow CURSOR FOR 
  SELECT SourceTableName,SourceIdFieldName,SourceNameFieldName,TargetTableName,TargetIdFieldName,TargetNameFieldName
  FROM db_redundancy.TableFieldMap;
  /*设置终止标记*/
  DECLARE CONTINUE HANDLER FOR SQLSTATE '02000' SET Done = 1;
  /*打开游标*/
  OPEN curRow;
    /*循环取出数据*/
    FETCH NEXT FROM curRow INTO vSourceTableName,vSourceIdFieldName,vSourceNameFieldName,vTargetTableName,vTargetIdFieldName,vTargetNameFieldName;
    WHILE Done<>1 DO
       #获取需要更新的数据
       SELECT SourceNameFieldNewValue,SourceIdFieldValue INTO vnewValue,vSourceIdFieldValue FROM db_redundancy.TableFieldValueModifyLog 
       WHERE  IsProcess=0 AND SourceTableName=vSourceTableName AND SourceIdFieldName=vSourceIdFieldName AND SourceNameFieldName=vSourceNameFieldName
       ORDER BY CreateDate DESC  limit 1;
       IF ISNULL(vnewValue) <> NULL || LENGTH(trim(vnewValue))>1 THEN
         #拼接语句
         SET vstrSql=CONCAT(' UPDATE ',vTargetTableName,' SET ', vTargetNameFieldName ,' = "',vnewValue,'" WHERE ', vTargetIdFieldName ,' = ', vSourceIdFieldValue,';');
         #注意很重要，将连成成的字符串赋值给一个变量（可以之前没有定义，但要以@开头）
         SET @vSql= vstrSql;
         #预处理需要执行的动态SQL，其中stmt是一个变量
         PREPARE stmt  FROM @vSql;
         #执行语句
         EXECUTE stmt ;
         #释放语句
         DEALLOCATE PREPARE  stmt;
         #更新历史表中状态标记
         UPDATE db_redundancy.TableFieldValueModifyLog SET IsProcess=1 WHERE IsProcess=0 AND SourceTableName=vSourceTableName AND SourceIdFieldName=vSourceIdFieldName AND SourceIdFieldValue=vSourceIdFieldValue;
       END IF;
       #重置数据
       SET vnewValue='';
       SET vstrSql='';
      FETCH NEXT FROM curRow INTO vSourceTableName,vSourceIdFieldName,vSourceNameFieldName,vTargetTableName,vTargetIdFieldName,vTargetNameFieldName;
    END WHILE;
  /*关闭游标*/
  CLOSE curRow;
END

在此记录一下，方便以后查询以及他人参照。