多表删除问题
输入命令： SELECT a.goods_id,a.goods_name FROM tdb_goods AS a LEFT JOIN (SELECT goods_id,goods_name FROM tdb_goods GROUP BY goods_name HAVING COUNT(goods_name)>1) AS b ON a.goods_name = b.goods_name ;
显示的是tdb_goods 的所有选项
但是在后面加上WHERE a.goods_id > b.goods_id，就只显示两条结果
命令：SELECT a.goods_id,a.goods_name FROM tdb_goods AS a LEFT JOIN (SELECT goods_id,goods_name FROM tdb_goods GROUP BY goods_name HAVING COUNT(goods_name)>1) AS b ON a.goods_name = b.goods_name WHERE a.goods_id > b.goods_id;
结果：
+----------+-------------------------+
| goods_id | goods_name |
+----------+-------------------------+
| 26 | HMZ-T3W 头戴显示设备
| 27 | 玄龙精英版 笔记本散热器
+----------+-------------------------+
2 rows in set (0.00 sec)
前后只是差了一个条件，如果把LEFT JION 改成RIGHT JION 或者 INNER JION 我都可以理解，就是LEFT JION 不明白，求各位大神指点迷津。
