mysql or语句的优化

Question

问题遇到的现象和发生背景

MySQL 如何修改SQL语句，去掉语句中的or，因为有or导致索引失效

问题相关代码，请勿粘贴截图

select bid from book a ,querybook b where ( b.bname in (a.bname) or b.bname = "" ) and
(b.bauthor in (a.bauthor) or b.bauthor = "" ) and
(b.barea in (a.barea) or b.barea = "" )

SQL作用是当查询条件为空时默认查询全部数据，不为空是则按照条件进行查询

Answer 1

首先，or 条件是同一个索引字段，走索引，不同才不走。
然后，题主的写法很奇怪，那我就在奇怪的基础上做改动，把or去掉：
select bid from book a ,querybook b where b.bname in (a.bname, "") and
(b.bauthor in (a.bauthor, "")) and
(b.barea in (a.barea, ""))