如果删除小表,不担心效率,可以用下面方式删除,
http://jimmy9495.iteye.com/admin/blogs/2072785
但是用上面的sql如果想在大表操作删除,肯定是不行的。
查看表中imsi除了空以外重复的数目。
SELECT COUNT(t.`imsi`),t.`imsi` FROM `boss_t_tour` t WHERE t.imsi <> '' GROUP BY t.`imsi` HAVING COUNT(t.`imsi`) >1
mysql大数据表中的快速删除部分数据办法:
1.创建删除重复的存储过程
DELIMITER $$ USE `bossdb` $$ DROP PROCEDURE IF EXISTS `del` $$ CREATE DEFINER = `root` @`localhost` PROCEDURE `del` () BEGIN /** 定义后面循环用到的变量*/ DECLARE coun1 INT ; DECLARE count2 INT ; DROP TABLE IF EXISTS tmp_imsi; DROP TABLE IF EXISTS tmp_all; DROP TABLE IF EXISTS tmp_keep; DROP TABLE IF EXISTS tmp_delete; /** 创建临时表*/ CREATE TABLE tmp_imsi AS SELECT t.imsi AS imsi FROM boss_t_tour t WHERE t.imsi <> '' GROUP BY t.imsi HAVING COUNT(t.imsi) >1; CREATE TABLE tmp_all AS SELECT t.id,t.imsi AS imsi FROM boss_t_tour t WHERE t.imsi IN (SELECT imsi FROM tmp_imsi); CREATE TABLE tmp_keep AS SELECT MIN(a.id) AS id FROM tmp_all a GROUP BY a.imsi; CREATE TABLE tmp_delete AS SELECT a.id AS id FROM tmp_all a WHERE a.id NOT IN (SELECT id FROM tmp_keep) ; /** 先删除索引提高删除速度*/ ALTER TABLE `bossdb`.`boss_t_tour` DROP INDEX `imsi_index`, DROP INDEX `syncstatusInded`; /** 循环删除开始*/ /** 原计划用此子查询删除,DELETE FROM boss_t_tour WHERE EXISTS (SELECT 1 FROM tmp_delete WHERE boss_t_tour.id = tmp_delete.id);*/ /** 但是发现mysql子查询删除效率奇慢,本机测试主表150W数据 临时表8000条数据 删除3000条用了一个小时,效率太差不敢在生产环境使用。*/ /** 用下面的循环删除效率高很多,删除8000多条数据5分钟 */ SELECT COUNT(*) INTO coun1 FROM tmp_delete; WHILE coun1 > 0 DO SELECT id INTO count2 FROM tmp_delete LIMIT 1 ; DELETE FROM boss_t_tour WHERE id = count2 ; DELETE FROM tmp_delete WHERE id = count2 ; COMMIT ; SET coun1 = coun1 - 1 ; END WHILE ; /** 循环删除结束*/ /** 重建索引*/ ALTER TABLE `bossdb`.`boss_t_tour` ADD INDEX `imsi_index` (`imsi`), ADD INDEX `syncstatusInded` (`sync_status`); /** 删除临时表*/ DROP TABLE IF EXISTS tmp_imsi; DROP TABLE IF EXISTS tmp_all; DROP TABLE IF EXISTS tmp_keep; DROP TABLE IF EXISTS tmp_delete; END $$ DELIMITER ;
2.执行存储过程
CALL del();
本机执行5分钟完成。
写的过程中还发现个问题mysql的delete操作居然不能给 表定义别名。。。
MYSQL delete语句不支持别名? http://blog.chinaunix.net/uid-20639775-id-3167446.html