今天发现一个奇怪的问题，先看如下SQL语句：

SELECT
	a.num,
	b.num,
	a.depart
FROM
	(
		(
			SELECT
				count(depart_Id) AS num,
				depart_Id AS depart
			FROM
				tiku_class			
			GROUP BY
				depart_id
		) a
		JOIN (
			SELECT
				count(depart_id) AS num,
				depart_id AS depart
			FROM
				tiku_news			
			GROUP BY
				depart_id
		) b ON a.depart = b.depart
	)
ORDER BY
	b.num DESC

?直接在MySQL中运行返回如下结果：

?再看在程序中使用Hibernate的：

  SQLQuery query = session.createSQLQuery(sql);
  return query.list();

?的结果：

?可以发现b.num的值等于a.num

太奇怪了吧，打开Hibernate的show_sql选项，将打印的SQL在mysql中执行依然没问题，崩溃。。难道是Hibernate的Bug，没可能啊 ，网上搜索也没发现类似情况。

?

就在百思不得其解的时候，突然看见了这个：

我的SQL代码中明明写的是a.num 和b.num，怎么结果显示的是num 和num1呢？

难道是num 别名相同的原因？

将SQL语句改成这样：

SELECT
	a.numa,
	b.numb AS numb,
	a.depart
FROM
	(
		(
			SELECT
				count(depart_Id) AS numa,
				depart_Id AS depart
			FROM
				tiku_class			
			GROUP BY
				depart_id
		) a
		JOIN (
			SELECT
				count(depart_id) AS numb,
				depart_id AS depart
			FROM
				tiku_news			
			GROUP BY
				depart_id
		) b ON a.depart = b.depart
	)
ORDER BY
	numb DESC

?
?再次运行程序，Oh Yes！这次结果终于正确了！

?

具体原因目前还说不清楚，但是以后写SQL语句起别名还是要注意些啊，尽量不要起一样的别名啊
?