有的數據庫不支持intersect，except，所以交集，和差集使用嵌套查詢來做比較靠譜。 a表和b表具有完全一樣的結構 mysql> desc a; +-------+-------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------+-------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | tel | varchar(11) | YES | | NULL | | +-------+-------------+------+-----+---------+----------------+ 2 rows in set (0.00 sec)mysql> desc b; +-------+-------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------+-------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | tel | varchar(11) | YES | | NULL | | +-------+-------------+------+-----+---------+----------------+ 2 rows in set (0.01 sec)

a表和b表中的數據不同，現在要查詢a表和b表的電話號碼的交，并，差集：

mysql> select * from a; +----+------+ | id | tel | +----+------+ | 1 | 1 | | 2 | 2 | +----+------+ 2 rows in set (0.00 sec)mysql> select * from b; +----+------+ | id | tel | +----+------+ | 1 | 2 | | 2 | 3 | +----+------+ 2 rows in set (0.01 sec)

交集

//聯合查詢
mysql> select a.tel from a,b where a.tel = b.tel; +------+ | tel | +------+ | 2 | +------+ 1 row in set (0.00 sec)

//也可以使用嵌套查詢
mysql> select a.tel from a where a.tel in (select b.tel from b);
+------+
| tel? |
+------+
| 2??? |
+------+
1 row in set (0.00 sec)

//也可以
mysql> select a.tel from a where exists (select * from b where a.tel = b.tel);
+------+
| tel? |
+------+
| 2??? |
+------+

//當然intersect有可能是不支持的
mysql> select a.tel from a intersect select b.tel from b;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'select b.tel from b' at line

并集

//MySQL從4.0以后是支持union，union all的，其實實現union是非常復雜的 mysql> select a.tel from a union select b.tel from b; +------+ | tel | +------+ | 1 | | 2 | | 3 | +------+ 3 rows in set (0.00 sec)

//

差集

except所代表的差集，是在a中出現但是不在b中出現的記錄；

mysql> select a.tel from a where a.tel not in ( select b.tel from b); +------+ | tel | +------+ | 1 | +------+ 1 row in set (0.00 sec)
//同樣，except也不一定支持
mysql> select a.tel from a except select b.tel form b;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'select b.tel form b' at line

轉載于:https://www.cnblogs.com/fangpengchengbupter/p/9356070.html

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