当获取多行作为结果时，Mysql查询返回NULL值

Question

Below is my query

 SELECT `months`,SUM(`price`) AS price 
 FROM `billing` 
 WHERE months='January' AND months='Feb'

I am trying to get result but this query is returning value NULL

Answer 1

finally I got answer of my question ans is: SELECT months,sum(price) as price FROM billing GROUP BY months