mysql查询语句

各种查询条件：

 join condition where condition having

having查询条件的用法：

SELECT column_name, aggregate_function(column_name)FROM table_nameWHERE column_name operator valueGROUP BY column_nameHAVING aggregate_function(column_name) operator value

查询语句的执行顺序参考：

http://www.cnblogs.com/rollenholt/p/3776923.html