Question

如果我有两个这样的数据库表：

+-----------------+
| dog             |
+-----------------+
| id              |
| name            |
| size            |
+-----------------+

+-----------------+
| dog_color       |
+-----------------+
| id              |
| dog_id          |
| color           |
+-----------------+

我如何编写一个查询，以便结果返回所有具有黑色和白色的狗？狗也可以有其他颜色，但需要有黑色和白色。

Answer 1

select dog.*, count(dog_color.color) as num_colors from dog
inner join dog_color on dog_color.dog_id = dog.id
where color in ('black', 'white')
group by dog.id
HAVING COUNT(DISTINCT dog_color.color) = 2;

应该这样做。

样本数据和测试：

mysql> select * from dog; 
+------+-------+------+
| id   | name  | size |
+------+-------+------+
|    1 | fido  |    0 |
|    2 | ruff  |    0 |
|    3 | rover |    0 |
+------+-------+------+
3 rows in set (0.00 sec)

mysql> select * from dog_color;
+------+--------+-------+
| id   | dog_id | color |
+------+--------+-------+
|    1 |      1 | black |
|    2 |      1 | white |
|    3 |      1 | brown |
|    4 |      2 | black |
|    5 |      3 | white |
+------+--------+-------+
5 rows in set (0.00 sec)

mysql> select dog.*, count(dog_color.color) as num_colors from dog
    -> inner join dog_color on dog_color.dog_id = dog.id
    -> where color in ('black', 'white')
    -> group by dog.id
    -> having num_colors = 2;
+------+------+------+------------+
| id   | name | size | num_colors |
+------+------+------+------------+
|    1 | fido |    0 |          2 |
+------+------+------+------------+
1 row in set (0.00 sec)

Answer 2

使用MySQL 5.1.x在下面测试的解决方案，返回至少具有白色和黑色颜色的所有狗：

SELECT dog.*,
       group_concat(dc_all.color) AS colors
FROM dog
JOIN dog_color as dc_white on (dog.id = dc_white.dog_id AND dc_white.color = 'white')
JOIN dog_color as dc_black on (dog.id = dc_black.dog_id AND dc_black.color = 'black')
LEFT JOIN dog_color as dc_all on (dog.id = dc_all.dog_id);

Answer 3

select distinct
  d.id
  , d.name
  , d.size
from
  dog d
  inner join dog_color c1
    on d.id = c1.dog_id 
    and c1.color in ('white')
  inner join dog_color c2
    on d.id = c2.dog_id 
    and c2.color in ('black')

SQL：根据另一个具有多个匹配的表的连接查询一个表

3 个答案: