SQL實現交,並,差操做

有的數據庫不支持intersect,except,因此交集,和差集使用嵌套查詢來作比較靠譜。
a表和b表具備徹底同樣的結構
 
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表中的數據不一樣,如今要查詢a表和b表的電話號碼的交,並,差集:mysql

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sql

//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)

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

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

//固然intersect有多是不支持的
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

並集數據庫

//MySQL從4.0之後是支持union,union all的,其實實現union是很是複雜的
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spa

except所表明的差集,是在a中出現可是不在b中出現的記錄;code

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)//一樣,except也不必定支持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 
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