optimizer_switch=derived_merge=off

[yehlu]

http://stackoverflow.com/questions/3773 ... -mysql-5-7

https://dev.mysql.com/doc/refman/5.7/en ... tions.html

As can be read in the comments, @wchiquito has suggested to look at the optimizer_switch. In here I found that the switch derived_merge could be set to off, to fix this new, and in this specific case undesired, behaviour.

set session optimizer_switch='derived_merge=off'; fixes the problem.
(This can also be done with set global ... or be put in the my.cnf / my.ini)


https://read01.com/RR5gBM.html
在5.7中，由於採用了新的優化方式，我們需要使用 set optimizer_switch=』derived_merge=off』來禁止derived table合併到外層的Query中。
原文網址：https://read01.com/RR5gBM.html