如何使用MySql获得某个字段的前几位
1、select substr(datetime,1,7) from ticket
获得ticket表中datetime字段,从第一位开始的6位。如“2014-07-30”,查询结果是“2014-07”
2、select substr(datetime,3) from ticket
获得ticket表中datetime字段,从第三位开始的后几位。如“2014-07-30”,查询结果是“14-07-30”
4、select productName, sum(quantity) AS totalQuantity,substr(datetime,5,2) AS Month from ticket group by productId,substr(datetime,1,6);
两次分组