MySql動態生成SQL並執行

場景：由於一些表中設計了一些冗余字段，因此在主表修改了該冗余字段的值得時候，需要動態更新在其他表中冗余字段的值

BEGIN
    #Routine body goes here...
   
  /*SQL語句變量*/
  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); 

  /*更新數據*/
  DECLARE vnewValue VARCHAR(100);
  DECLARE vSourceIdFieldValue VARCHAR(100);

  DECLARE Done INT DEFAULT 0;
  /*聲明游標*/
  DECLARE curRow CURSOR FOR 
  SELECT SourceTableName,SourceIdFieldName,SourceNameFieldName,TargetTableName,TargetIdFieldName,TargetNameFieldName
  FROM db_redundancy.TableFieldMap;
  /*設置終止標記*/
  DECLARE CONTINUE HANDLER FOR SQLSTATE '02000' SET Done = 1;
  /*打開游標*/
  OPEN curRow;
    /*循環取出數據*/
    FETCH NEXT FROM curRow INTO vSourceTableName,vSourceIdFieldName,vSourceNameFieldName,vTargetTableName,vTargetIdFieldName,vTargetNameFieldName;
    WHILE Done<>1 DO
       #獲取需要更新的數據
       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
         #拼接語句
         SET vstrSql=CONCAT(' UPDATE ',vTargetTableName,' SET ', vTargetNameFieldName ,' = "',vnewValue,'" WHERE ', vTargetIdFieldName ,' = ', vSourceIdFieldValue,';');
         #注意很重要，將連成成的字符串賦值給一個變量（可以之前沒有定義，但要以@開頭）
         SET @vSql= vstrSql;
         #預處理需要執行的動態SQL，其中stmt是一個變量
         PREPARE stmt  FROM @vSql;
         #執行語句
         EXECUTE stmt ;
         #釋放語句
         DEALLOCATE PREPARE  stmt;
         #更新歷史表中狀態標記
         UPDATE db_redundancy.TableFieldValueModifyLog SET IsProcess=1 WHERE IsProcess=0 AND SourceTableName=vSourceTableName AND SourceIdFieldName=vSourceIdFieldName AND SourceIdFieldValue=vSourceIdFieldValue;
       END IF;
       #重置數據
       SET vnewValue='';
       SET vstrSql='';
      FETCH NEXT FROM curRow INTO vSourceTableName,vSourceIdFieldName,vSourceNameFieldName,vTargetTableName,vTargetIdFieldName,vTargetNameFieldName;
    END WHILE;
  /*關閉游標*/
  CLOSE curRow;
END

在此記錄一下，方便以后查詢以及他人參照。