連線包括內連線和外連線。
通過連線運算子可以實現多個表查詢。
1 內連線查詢
mysql> select * from students;
+----+--------+-------+------+------+
| id | number | name | *** | age |
+----+--------+-------+------+------+
| 1 | 1111 | lily | w | 12 |
| 2 | 1112 | lucy | w | 11 |
| 3 | 1113 | lilei | m | 13 |
| 4 | 1114 | bird | null | 33 |
+----+--------+-------+------+------+
4 rows in set (0.00 sec)
mysql> select * from scores;
+----+--------+---------+---------+
| id | number | chinese | english |
+----+--------+---------+---------+
| 1 | 1111 | 99 | 87 |
| 2 | 1112 | 66 | 87 |
| 3 | 1113 | 55 | 100 |
| 4 | 1116 | 55 | 77 |
+----+--------+---------+---------+
4 rows in set (0.00 sec)
mysql> select name,age,scores.chinese,scores.english from students inner join scores on students.number=scores.number;
+-------+------+---------+---------+
| name | age | chinese | english |
+-------+------+---------+---------+
| lily | 12 | 99 | 87 |
| lucy | 11 | 66 | 87 |
| lilei | 13 | 55 | 100 |
+-------+------+---------+---------+
3 rows in set (0.00 sec)
外連線又分為左外連線和右外連線。
left join： 會返還左邊表中所有資料和 與右表中與連線字段匹配的資料。 right join與之相似。
2.1 左連線示例
mysql> select name,age,scores.chinese,scores.english from students left outer join scores on students.number=scores.number;
+-------+------+---------+---------+
| name | age | chinese | english |
+-------+------+---------+---------+
| lily | 12 | 99 | 87 |
| lucy | 11 | 66 | 87 |
| lilei | 13 | 55 | 100 |
| bird | 33 | null | null |
+-------+------+---------+---------+
4 rows in set (0.00 sec)
mysql> select name,age,scores.chinese from students right outer join scores on students.number=scores.number;
+-------+------+---------+
| name | age | chinese |
+-------+------+---------+
| lily | 12 | 99 |
| lucy | 11 | 66 |
| lilei | 13 | 55 |
| null | null | 55 |
+-------+------+---------+
4 rows in set (0.00 sec)
mysql連線查詢例項 MySQL連線查詢例項詳解
建立表suppliers create table suppliers s id int not null auto increment,s name char 50 not null,s city char 50 null,s zip char 10 null,s call char 50 not...
mysql連線查詢例項 MySQL連線查詢例項詳解
建立表suppliers create table suppliers s id int not null auto increment,s name char 50 not null,s city char 50 null,s zip char 10 null,s call char 50 not...
mysql連線查詢on MySQL連線查詢例項詳解
建立表suppliers create table suppliers s id int not null auto increment,s name char 50 not null,s city char 50 null,s zip char 10 null,s call char 50 not...