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 '' 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。