前言 某天,突然被问到 MySQL 的 next-key lock,我瞬间的反应就是: 这都是啥啥啥??? 这一个截图我啥也看不出来呀? 仔细一看,好像似曾相识,这不是<MySQL 45 讲>里面的内容么? 什么是 next-key lock A next-key lock is a combination of a record lock on the index record and a gap lock on the gap before the index record. 官网的解释大
mysql select column default value if is null SELECT `w`.`city` AS `city`, `w`.`city_en` AS `city_en`, `w`.`date_y` AS `date_y`, `w`.`week` AS `week`, `w`.`cityid` AS `cityid`, `w`.`temp1` AS `temp1`, `w`.`temp2` AS `temp2`, `w`.`temp3` AS `temp3`, `w
问题说明: 最近遇到一个问题,多个WORKER同时向MYSQL数据库请求任务,如何实现互斥?例如: SELECT * FROM student WHERE id > 10 LIMIT 100; UPDATE student SET status = 1 WHERE id > 10 LIMIT 100; 当有多个WORKER执行上面两条语句,那么很可能都执行同样的数据,造成线上问题,比如WORDER1执行SELECT之后,还没有执行UPDATE之前,WORDER2也执行了SELECT语句,造成问
mysql select自增变量(包括读取当前第几行) SET @rownum =0;select id,@rownum := @rownum +1 as i from ceshi order by dd desc,id desc; 变量是直接输出在结果集的 SET @rownum =0; @rownum :=1 这2个个是变量赋值的方式 SET @rownum =0;select i from(select id,dd,@rownum := @rownum +1 as i from ceshi