mysql - 按 RAND() LIMIT 100 更新订单

Question

我想为一个字段设置一个不同的文本我正在尝试那种代码

SET  @rand = 100;
UPDATE myTable SET  name = 'a'  ORDER BY RAND() LIMIT @rand;
UPDATE myTable SET  name = 'b'  ORDER BY RAND() LIMIT @rand;
UPDATE myTable SET  name = 'c'  ORDER BY RAND() LIMIT @rand;

我遇到了一个错误

1221 - Incorrect usage of UPDATE and ORDER BY

感谢帮助

Answer 1

你为什么要用 RAND() 更新。它会减慢您的更新速度吗？按索引列(如主键)排序。这是一个性能 killer 。

当您确切知道要一次更新多少条记录时，设置 @rand = 100 有什么意义？

我假设您有一个名为 id

的主键

update myTable set  name = 'a'  order by id desc limit 100;
update myTable set  name = 'b'  order by id desc limit 100;
update myTable set  name = 'c'  order by id desc limit 100;