如何建立索引

Question

如何建立索引
1 select * from a  where  email='[email protected]' order by name
2 select * from a  where  email='[email protected]' group by firstname, secondname order by name
3  select * from a  where email='[email protected]' group by firstname, secondname
这里email有重复的  ， name  firstname, secondname  等都有大量重复

Answer 1

1 select * from a  where  email='[email protected]' order by name
(email,name)

2 select * from a  where  email='[email protected]' group by firstname, secondname order by name
(email,firstname,secondname,name)

3 select * from a  where  email='[email protected]' group by firstname, secondname
(email,firstname,secondname)所以建议创建索引
(email,name)
(email,firstname,secondname,name)
这两个索引。