SQL学习第5次
摘要:
1、GROUP BY ,分组。很有用SELECT LastName,SUM(gongzi) FROM person GROUP BY LastName;#按LastName分组, 查看每组的工资。2、HAVING,where无法和合计函数一起用。前面提过,合计函数就是输入多个值,输出1个值。如SUM(),COUNT(),MAX(),AVG()等。SELECT LastName,SUM(gongzi... 阅读全文
posted @ 2013-04-18 17:36 百舸争流info 阅读(131) 评论(0) 推荐(0) 编辑