1 or (to be confirmed), in (to be confirmed)
2 like '%abc' 或者 like‘%abc%’
3 where num / 2 = 100 or subString (a, 1,3) = 'ab'
4 where id !=2 或者 where id <> 2
5 where name is null
6 composite index abc, a used, b less than, less than C, ab effective, BA active, inactive, a or b, ac effective, bc invalid, ABC effective
https://blog.csdn.net/Abysscarry/article/details/80792876
7 Mysql composite index used when the condition has not https://blog.csdn.net/u010002184/article/details/85195328 or
Original: https: //blog.csdn.net/u010002184/article/details/89388600