实现清除Mysql数据库的特定表无用数据的存储过程

第一次玩存储过程，遇到好多问题，记录一下供日后参考。

说明：其中 logtable 是一个临时表用来调试用的，有“index,log1，log2，log3，log4，log5，log6，log7，log8”九个字段。

#定义存储过程
DROP PROCEDURE IF EXISTS ClearUnusefulData;
CREATE PROCEDURE ClearUnusefulData()

BEGIN

       DECLARE tablesNameVar VARCHAR (100);
       DECLARE done INT DEFAULT 0;
       DECLARE datatime VARCHAR (15) DEFAULT '201910010000';
       DECLARE columnVar VARCHAR (100) DEFAULT '0';
       DECLARE loginfo VARCHAR (100) DEFAULT '0';
       #SET datatime ='201910010000';

    #查出要清理数据的特定表
       DECLARE tableName CURSOR FOR SELECT   table_name FROM information_schema.TABLES
         WHERE table_schema = '联网'
              AND table_name NOT LIKE '%设定表'
      #        AND table_name LIKE '%日统计%';
               AND table_name NOT LIKE '%实时%'
               AND table_name NOT LIKE '%巡检%';

DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;

#打开游标
OPEN tableName;

       group_loop :LOOP
           FETCH tableName INTO tablesNameVar;
           IF done = 1 THEN
        #日志
        INSERT INTO logtable(log1) SELECT 'done==1 so leave loop';
               LEAVE group_loop;
           END IF;

           #拼接sql 查询需要的数据复制到×_copy表
      #日志
      INSERT INTO logtable(log1) SELECT tablesNameVar;

      #判断该表中是否有datatime列
      SET @columnVar1 = 0;
      SET @var_sql = concat(
                   'SELECT count(*) into @columnVar1 ',
          " FROM information_schema.columns WHERE table_schema = DATABASE() AND table_name = '",
                   tablesNameVar,
                   "' AND column_name = 'datatime'"
               );

           PREPARE s FROM @var_sql;
           EXECUTE s;
           DEALLOCATE PREPARE s;

#日志
UPDATE logtable SET log5 = @columnVar1 WHERE log1 = tablesNameVar;

      IF @columnVar1=1 THEN
               SET @var_sql1 = concat(
                       'CREATE TABLE ',
                       tablesNameVar,
                       '_COPY ',
                       'SELECT * FROM ',
                       tablesNameVar,
                       ' WHERE DATATIME > ',
                       datatime
                   );

               SET @var_sql1_count = concat(
                       'SELECT count(*) into @columnVar1_count FROM ',
                       tablesNameVar,
                       ' WHERE DATATIME > ',
                       datatime
                   );
           ELSE
               SET @var_sql1 = concat(
                       'CREATE TABLE ',
                       tablesNameVar,
                       '_COPY ',
                       'SELECT * FROM ',
                       tablesNameVar,
                       ' WHERE 统计日期 > ',
                       LEFT(datatime,8)
                   );

          SET @var_sql1_count = concat(
                       'SELECT count(*) into @columnVar1_count FROM ',
                       tablesNameVar,
                       ' WHERE 统计日期 > ',
                       LEFT(datatime,8)
                   );
      END IF;

           PREPARE s1_count FROM @var_sql1_count;
           EXECUTE s1_count;
           DEALLOCATE PREPARE s1_count;

           UPDATE logtable SET log7 = @columnVar1_count WHERE log1 = tablesNameVar;

      #判断该表是否有要备份的数据，没有要备份的数据直接清空该表，进入下一个循环，
           IF @columnVar1_count<1 THEN
               SET @clear_sql = concat(
                   'TRUNCATE TABLE ',
                   tablesNameVar
               );
               PREPARE s_clear FROM @clear_sql;
               EXECUTE s_clear;
               DEALLOCATE PREPARE s_clear;
        #日志
        UPDATE logtable SET log7 = CONCAT(@columnVar1_count,': no userful data,so continue next loop') WHERE log1 = tablesNameVar;
        ITERATE group_loop;
      END IF;

      #把要保留的数据拷贝到新表 ×_copy 中
           PREPARE s1 FROM @var_sql1;
           EXECUTE s1;
           DEALLOCATE PREPARE s1;
      #日志
      SET loginfo = CONCAT('Copy useful data from ',tablesNameVar,' successful!');
      UPDATE logtable SET log2 = loginfo WHERE log1 = tablesNameVar;

           #删除原有表
           SET @var_sql2 = concat(
               'DROP TABLE ',
               tablesNameVar
           );

           PREPARE s2 FROM @var_sql2;
           EXECUTE s2;
           DEALLOCATE PREPARE s2;
      #日志
           SET loginfo = CONCAT('drop the old table：',tablesNameVar);
      UPDATE logtable SET log3 = loginfo WHERE log1 = tablesNameVar;

      #把×_copy表重命名为原表
           SET @var_sql3 = concat(
               'RENAME TABLE ',
               tablesNameVar,
               '_COPY ',
               'TO ',
               tablesNameVar
           );

           PREPARE s3 FROM @var_sql3;
           EXECUTE s3;
           DEALLOCATE PREPARE s3;
      #日志
      SET loginfo = CONCAT('rename the copy table：',tablesNameVar,'_copy to original name');
      UPDATE logtable SET log4 = loginfo WHERE log1 = tablesNameVar;

END LOOP group_loop;

CLOSE tableName;

END

其中遇到的坑：

1.当在游标循环过程中select的结果集如果为空，就会触发游标continue handler for not found 提前将done置为1，导致提前退出游标。
2.游标循环中出现 select into 赋值为 null 的时候，循环也会提前退出。

来源：oschina

链接：https://my.oschina.net/u/267603/blog/4514087

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mysql