怎样加快like 的速度?
20~30张表,每张表50~60万行记录,表结构都相同。其中有4个字段,假设是a1,a2,a3,a4,类型都是nvarchar(30)。
我的问题是:
select * from table1 where a1 like '%str%' or a2 like %str%' or a3 like %str% or a4 like %str% union all
select * from table2 where a1 like '%str%' or a2 like %str%' or a3 like %str% or a4 like %str% union all
select * from table3 where a1 like '%str%' or a2 like %str%' or a3 like %str% or a4 like %str% union all
.........
select * from table30 where a1 like '%str%' or a2 like %str%' or a3 like %str% or a4 like %str%
str: 一个给定的字符串
怎样利用索引或者其它方法加快查询速度?