MySQL删除所有记录未选中

Question

我试图删除除最近25个基于时间戳的所有条目。我尝试这样做：

DELETE FROM `chat` WHERE `IndexNo` NOT IN(SELECT `IndexNo` FROM `chat` ORDER BY `Timestamp` DESC LIMIT 25) 

生成此错误：

#1235 - This version of MySQL doesn't yet support 'LIMIT & IN/ALL/ANY/SOME subquery' 

有没有办法做到这一点？

Answer 1

你不能依靠LIMIT在IN/ALL/ANY/SOME子查询，而是可以使用多删除语法：

DELETE 
    `chat` 
FROM 
    `chat` 
    LEFT JOIN (SELECT `IndexNo` FROM `chat` ORDER BY `Timestamp` DESC LIMIT 25) AS `selected` 
     ON `chat`.`IndexNo`=`selected`.`IndexNo` 
WHERE 
    `selected`.`IndexNo` IS NULL; 

- 根据manual，这将因为MySQL 5.0中工作

Answer 2

这是一个有关子查询我猜的更一般的问题。尝试看看这里：Problem with LIMIT & IN/ALL/ANY/SOME subquery