MySQL连接实例

mysql> use test
Database changed
mysql> show tables;
Empty set (0.00 sec)


mysql> create table person( id smallint unsigned NOT NULL AUTO_INCREMENT, name v
archar(30), primary key(id));
Query OK, 0 rows affected (0.12 sec)


mysql> create table score(id smallint unsigned NOT NULL, score int);
Query OK, 0 rows affected (0.14 sec)


mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| person         |
| score          |
+----------------+
2 rows in set (0.00 sec)


mysql> insert into person(name) values ('zrx'),('genius'),('stupid');
Query OK, 3 rows affected (0.11 sec)
Records: 3  Duplicates: 0  Warnings: 0


mysql> select * from person;
+----+--------+
| id | name   |
+----+--------+
|  1 | zrx    |
|  2 | genius |
|  3 | stupid |
+----+--------+
3 rows in set (0.00 sec)


mysql> insert into score values (1, 9),(2, 100);
Query OK, 2 rows affected (0.11 sec)
Records: 2  Duplicates: 0  Warnings: 0


mysql> insert into score values (4,20);
Query OK, 1 row affected (0.11 sec)


mysql> insert into score values (1,1);
Query OK, 1 row affected (0.11 sec)


mysql> select * from score;
+----+-------+
| id | score |
+----+-------+
|  1 |     9 |
|  2 |   100 |
|  4 |    20 |
|  1 |     1 |
+----+-------+
4 rows in set (0.00 sec)


mysql> select * from person inner join score ;
+----+--------+----+-------+
| id | name   | id | score |
+----+--------+----+-------+
|  1 | zrx    |  1 |     9 |
|  2 | genius |  1 |     9 |
|  3 | stupid |  1 |     9 |
|  1 | zrx    |  2 |   100 |
|  2 | genius |  2 |   100 |
|  3 | stupid |  2 |   100 |
|  1 | zrx    |  4 |    20 |
|  2 | genius |  4 |    20 |
|  3 | stupid |  4 |    20 |
|  1 | zrx    |  1 |     1 |
|  2 | genius |  1 |     1 |
|  3 | stupid |  1 |     1 |
+----+--------+----+-------+
12 rows in set (0.00 sec)


mysql> select * from person inner join score where person.id=score.id;
+----+--------+----+-------+
| id | name   | id | score |
+----+--------+----+-------+
|  1 | zrx    |  1 |     9 |
|  2 | genius |  2 |   100 |
|  1 | zrx    |  1 |     1 |
+----+--------+----+-------+
3 rows in set (0.00 sec)


mysql> select * from (person, score);
+----+--------+----+-------+
| id | name   | id | score |
+----+--------+----+-------+
|  1 | zrx    |  1 |     9 |
|  2 | genius |  1 |     9 |
|  3 | stupid |  1 |     9 |
|  1 | zrx    |  2 |   100 |
|  2 | genius |  2 |   100 |
|  3 | stupid |  2 |   100 |
|  1 | zrx    |  4 |    20 |
|  2 | genius |  4 |    20 |
|  3 | stupid |  4 |    20 |
|  1 | zrx    |  1 |     1 |
|  2 | genius |  1 |     1 |
|  3 | stupid |  1 |     1 |
+----+--------+----+-------+
12 rows in set (0.00 sec)


mysql> select * from (person, score) using (id);
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 'using
 (id)' at line 1
mysql> select * from (person, score) where person.id=score.id;
+----+--------+----+-------+
| id | name   | id | score |
+----+--------+----+-------+
|  1 | zrx    |  1 |     9 |
|  2 | genius |  2 |   100 |
|  1 | zrx    |  1 |     1 |
+----+--------+----+-------+
3 rows in set (0.00 sec)


mysql> select * from person inner join score using (id);
+----+--------+-------+
| id | name   | score |
+----+--------+-------+
|  1 | zrx    |     9 |
|  2 | genius |   100 |
|  1 | zrx    |     1 |
+----+--------+-------+
3 rows in set (0.00 sec)


mysql> select * from person natural join score;
+----+--------+-------+
| id | name   | score |
+----+--------+-------+
|  1 | zrx    |     9 |
|  2 | genius |   100 |
|  1 | zrx    |     1 |
+----+--------+-------+
3 rows in set (0.00 sec)


mysql> select * from person left join score;
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 '' at
line 1
mysql> select * from person left join score where person.id=score.id;
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 'where
 person.id=score.id' at line 1
mysql> select * from person left join score using(id);
+----+--------+-------+
| id | name   | score |
+----+--------+-------+
|  1 | zrx    |     9 |
|  1 | zrx    |     1 |
|  2 | genius |   100 |
|  3 | stupid |  NULL |
+----+--------+-------+
4 rows in set (0.00 sec)


mysql> select * from person left join score on person.id=score.id;
+----+--------+------+-------+
| id | name   | id   | score |
+----+--------+------+-------+
|  1 | zrx    |    1 |     9 |
|  1 | zrx    |    1 |     1 |
|  2 | genius |    2 |   100 |
|  3 | stupid | NULL |  NULL |
+----+--------+------+-------+
4 rows in set (0.00 sec)


mysql> select * from person right join score on person.id=score.id;
+------+--------+----+-------+
| id   | name   | id | score |
+------+--------+----+-------+
|    1 | zrx    |  1 |     9 |
|    2 | genius |  2 |   100 |
| NULL | NULL   |  4 |    20 |
|    1 | zrx    |  1 |     1 |
+------+--------+----+-------+
4 rows in set (0.00 sec)


mysql> select * from person full outer join score on person.id=score.id;
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 'outer
 join score on person.id=score.id' at line 1
mysql> select * from person full join score on person.id=score.id;
ERROR 1054 (42S22): Unknown column 'person.id' in 'on clause'
mysql> select * from person full join score using(id);
+----+--------+-------+
| id | name   | score |
+----+--------+-------+
|  1 | zrx    |     9 |
|  2 | genius |   100 |
|  1 | zrx    |     1 |
+----+--------+-------+
3 rows in set (0.00 sec)


mysql> select * from person full join score on person.id=score.id;
ERROR 1054 (42S22): Unknown column 'person.id' in 'on clause'
mysql> select * from person p full join score s on p.id=s.id;
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 'full
join score s on p.id=s.id' at line 1
mysql> select * from person full outer join score using(id);
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 'outer
 join score using(id)' at line 1
mysql> select * from person left join score using(id) union select * from person
 right join score using (id);
+----+--------+--------+
| id | name   | score  |
+----+--------+--------+
|  1 | zrx    | 9      |
|  1 | zrx    | 1      |
|  2 | genius | 100    |
|  3 | stupid | NULL   |
|  1 | 9      | zrx    |
|  2 | 100    | genius |
|  4 | 20     | NULL   |
|  1 | 1      | zrx    |
+----+--------+--------+
8 rows in set (0.00 sec)


mysql> select * from person left join score on person.id=score.id union select *
 from person right join score on person.id=score.id;
+------+--------+------+-------+
| id   | name   | id   | score |
+------+--------+------+-------+
|    1 | zrx    |    1 |     9 |
|    1 | zrx    |    1 |     1 |
|    2 | genius |    2 |   100 |
|    3 | stupid | NULL |  NULL |
| NULL | NULL   |    4 |    20 |
+------+--------+------+-------+
5 rows in set (0.00 sec)


mysql>

MySQL本身不支持full join（全连接），但可以通过union来实现。