詳解mysql函數拼接查詢concat函數的使用方法

//查询表managefee_managefee的年year 和 month ,用concat函数拼成year-month。例如将2017和1 拼成2017-01。.
select CONCAT(a.year,&#39;-&#39;,if(a.month<=9,CONCAT(&#39;0&#39;,a.month),a.month))as date,a.* from managefee_managefee as a;

//查询managefee_managefee中时间段为2017-01到2017-07的数据
select * from
(
select CONCAT(a.year,&#39;-&#39;,if(a.month<=9,CONCAT(&#39;0&#39;,a.month),a.month))as date,a.* from managefee_managefee as a
) b
where b.date between &#39;2017-01&#39; and &#39;2017-07&#39;;