1

我有一个看起来像这样的表：

---------------------------
|housing_id | facility_id |
---------------------------
|    1      |      7      |
|    1      |      4      |
|    2      |      7      |
---------------------------

现在我想要做的是获取所有 Housing_id 的设施 ID 为 7 和 4。所以在这种情况下查询应该只返回 Housing_id 1。数据库是mysql。

4

3 回答 3

7

另一种方法是 -

SELECT housing_id
FROM mytable
WHERE facility_id IN (4,7)
GROUP BY housing_id
HAVING COUNT(DISTINCT facility_id) = 2

更新- 受 Josvic 评论的启发，我决定进行更多测试，并认为我会包括我的发现。

使用此查询的好处之一是很容易修改以包含更多设施 ID。如果您想查找所有具有 facility_ids 1、3、4 和 7 的 Housing_id，您只需执行以下操作 -

SELECT housing_id
FROM mytable
WHERE facility_id IN (1,3,4,7)
GROUP BY housing_id
HAVING COUNT(DISTINCT facility_id) = 4

所有这三个查询的性能因所采用的索引策略而有很大差异。无论使用何种索引，我都无法在我的测试数据集上从依赖子查询版本中获得合理的性能。

Tim 提供的自联接解决方案在给定两列上单独的单列索引的情况下表现非常好，但随着条件数量的增加，表现并不那么好。

这是我的测试表上的一些基本统计数据 - 500k 行 - 147963 个 Housing_ids，facility_id 的潜在值在 1 到 9 之间。

以下是用于运行所有这些测试的索引 -

SHOW INDEXES FROM mytable;
+---------+------------+---------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+
| Table   | Non_unique | Key_name            | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type |
+---------+------------+---------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+
| mytable |          0 | UQ_housing_facility |            1 | housing_id  | A         |      500537 |     NULL | NULL   |      | BTREE      |
| mytable |          0 | UQ_housing_facility |            2 | facility_id | A         |      500537 |     NULL | NULL   |      | BTREE      |
| mytable |          0 | UQ_facility_housing |            1 | facility_id | A         |          12 |     NULL | NULL   |      | BTREE      |
| mytable |          0 | UQ_facility_housing |            2 | housing_id  | A         |      500537 |     NULL | NULL   |      | BTREE      |
| mytable |          1 | IX_housing          |            1 | housing_id  | A         |      500537 |     NULL | NULL   |      | BTREE      |
| mytable |          1 | IX_facility         |            1 | facility_id | A         |          12 |     NULL | NULL   |      | BTREE      |
+---------+------------+---------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+

测试的第一个查询是依赖子查询 -

SELECT SQL_NO_CACHE DISTINCT housing_id
FROM mytable
WHERE housing_id IN (SELECT housing_id FROM mytable WHERE facility_id=4)
AND housing_id IN (SELECT housing_id FROM mytable WHERE facility_id=7);

17321 rows in set (9.15 sec)

+----+--------------------+---------+-----------------+----------------------------------------------------------------+---------------------+---------+------------+--------+---------------------------------------+
| id | select_type        | table   | type            | possible_keys                                                  | key                 | key_len | ref        | rows   | Extra                                 |
+----+--------------------+---------+-----------------+----------------------------------------------------------------+---------------------+---------+------------+--------+---------------------------------------+
|  1 | PRIMARY            | mytable | range           | NULL                                                           | IX_housing          | 4       | NULL       | 500538 | Using where; Using index for group-by |
|  3 | DEPENDENT SUBQUERY | mytable | unique_subquery | UQ_housing_facility,UQ_facility_housing,IX_housing,IX_facility | UQ_housing_facility | 8       | func,const |      1 | Using index; Using where              |
|  2 | DEPENDENT SUBQUERY | mytable | unique_subquery | UQ_housing_facility,UQ_facility_housing,IX_housing,IX_facility | UQ_housing_facility | 8       | func,const |      1 | Using index; Using where              |
+----+--------------------+---------+-----------------+----------------------------------------------------------------+---------------------+---------+------------+--------+---------------------------------------+

SELECT SQL_NO_CACHE DISTINCT housing_id
FROM mytable
WHERE housing_id IN (SELECT housing_id FROM mytable WHERE facility_id=1)
AND housing_id IN (SELECT housing_id FROM mytable WHERE facility_id=3)
AND housing_id IN (SELECT housing_id FROM mytable WHERE facility_id=4)
AND housing_id IN (SELECT housing_id FROM mytable WHERE facility_id=7);

567 rows in set (9.30 sec)

+----+--------------------+---------+-----------------+----------------------------------------------------------------+---------------------+---------+------------+--------+---------------------------------------+
| id | select_type        | table   | type            | possible_keys                                                  | key                 | key_len | ref        | rows   | Extra                                 |
+----+--------------------+---------+-----------------+----------------------------------------------------------------+---------------------+---------+------------+--------+---------------------------------------+
|  1 | PRIMARY            | mytable | range           | NULL                                                           | IX_housing          | 4       | NULL       | 500538 | Using where; Using index for group-by |
|  5 | DEPENDENT SUBQUERY | mytable | unique_subquery | UQ_housing_facility,UQ_facility_housing,IX_housing,IX_facility | UQ_housing_facility | 8       | func,const |      1 | Using index; Using where              |
|  4 | DEPENDENT SUBQUERY | mytable | unique_subquery | UQ_housing_facility,UQ_facility_housing,IX_housing,IX_facility | UQ_housing_facility | 8       | func,const |      1 | Using index; Using where              |
|  3 | DEPENDENT SUBQUERY | mytable | unique_subquery | UQ_housing_facility,UQ_facility_housing,IX_housing,IX_facility | UQ_housing_facility | 8       | func,const |      1 | Using index; Using where              |
|  2 | DEPENDENT SUBQUERY | mytable | unique_subquery | UQ_housing_facility,UQ_facility_housing,IX_housing,IX_facility | UQ_housing_facility | 8       | func,const |      1 | Using index; Using where              |
+----+--------------------+---------+-----------------+----------------------------------------------------------------+---------------------+---------+------------+--------+---------------------------------------+

接下来是我使用 GROUP BY ... HAVING COUNT ... 的版本

SELECT SQL_NO_CACHE housing_id
FROM mytable
WHERE facility_id IN (4,7)
GROUP BY housing_id
HAVING COUNT(DISTINCT facility_id) = 2;

17321 rows in set (0.79 sec)

+----+-------------+---------+-------+---------------------------------+-------------+---------+------+--------+------------------------------------------+
| id | select_type | table   | type  | possible_keys                   | key         | key_len | ref  | rows   | Extra                                    |
+----+-------------+---------+-------+---------------------------------+-------------+---------+------+--------+------------------------------------------+
|  1 | SIMPLE      | mytable | range | UQ_facility_housing,IX_facility | IX_facility | 4       | NULL | 198646 | Using where; Using index; Using filesort |
+----+-------------+---------+-------+---------------------------------+-------------+---------+------+--------+------------------------------------------+

SELECT SQL_NO_CACHE housing_id
FROM mytable
WHERE facility_id IN (1,3,4,7)
GROUP BY housing_id
HAVING COUNT(DISTINCT facility_id) = 4;

567 rows in set (1.25 sec)

+----+-------------+---------+-------+---------------------------------+-------------+---------+------+--------+------------------------------------------+
| id | select_type | table   | type  | possible_keys                   | key         | key_len | ref  | rows   | Extra                                    |
+----+-------------+---------+-------+---------------------------------+-------------+---------+------+--------+------------------------------------------+
|  1 | SIMPLE      | mytable | range | UQ_facility_housing,IX_facility | IX_facility | 4       | NULL | 407160 | Using where; Using index; Using filesort |
+----+-------------+---------+-------+---------------------------------+-------------+---------+------+--------+------------------------------------------+

最后但并非最不重要的自我加入 -

SELECT SQL_NO_CACHE a.housing_id
FROM mytable a
INNER JOIN mytable b
    ON a.housing_id = b.housing_id
WHERE a.facility_id = 4 AND b.facility_id = 7;

17321 rows in set (1.37 sec)

+----+-------------+-------+--------+----------------------------------------------------------------+---------------------+---------+-------------------------+-------+-------------+
| id | select_type | table | type   | possible_keys                                                  | key                 | key_len | ref                     | rows  | Extra       |
+----+-------------+-------+--------+----------------------------------------------------------------+---------------------+---------+-------------------------+-------+-------------+
|  1 | SIMPLE      | b     | ref    | UQ_housing_facility,UQ_facility_housing,IX_housing,IX_facility | IX_facility         | 4       | const                   | 94598 | Using index |
|  1 | SIMPLE      | a     | eq_ref | UQ_housing_facility,UQ_facility_housing,IX_housing,IX_facility | UQ_housing_facility | 8       | test.b.housing_id,const |     1 | Using index |
+----+-------------+-------+--------+----------------------------------------------------------------+---------------------+---------+-------------------------+-------+-------------+

SELECT SQL_NO_CACHE a.housing_id
FROM mytable a
INNER JOIN mytable b
    ON a.housing_id = b.housing_id
INNER JOIN mytable c
    ON a.housing_id = c.housing_id
INNER JOIN mytable d
    ON a.housing_id = d.housing_id
WHERE a.facility_id = 1
AND b.facility_id = 3
AND c.facility_id = 4
AND d.facility_id = 7;

567 rows in set (1.64 sec)

+----+-------------+-------+--------+----------------------------------------------------------------+---------------------+---------+-------------------------+-------+--------------------------+
| id | select_type | table | type   | possible_keys                                                  | key                 | key_len | ref                     | rows  | Extra                    |
+----+-------------+-------+--------+----------------------------------------------------------------+---------------------+---------+-------------------------+-------+--------------------------+
|  1 | SIMPLE      | b     | ref    | UQ_housing_facility,UQ_facility_housing,IX_housing,IX_facility | IX_facility         | 4       | const                   | 93782 | Using index              |
|  1 | SIMPLE      | d     | eq_ref | UQ_housing_facility,UQ_facility_housing,IX_housing,IX_facility | UQ_housing_facility | 8       | test.b.housing_id,const |     1 | Using index              |
|  1 | SIMPLE      | c     | eq_ref | UQ_housing_facility,UQ_facility_housing,IX_housing,IX_facility | UQ_housing_facility | 8       | test.b.housing_id,const |     1 | Using index              |
|  1 | SIMPLE      | a     | eq_ref | UQ_housing_facility,UQ_facility_housing,IX_housing,IX_facility | UQ_housing_facility | 8       | test.d.housing_id,const |     1 | Using where; Using index |
+----+-------------+-------+--------+----------------------------------------------------------------+---------------------+---------+-------------------------+-------+--------------------------+
于 2012-04-12T10:26:54.750 回答
4 
SELECT housing_id
FROM mytable
WHERE housing_id IN (SELECT housing_id FROM mytable WHERE facility_id=4)
AND housing_id IN (SELECT housing_id FROM mytable WHERE facility_id=7)
于 2012-04-12T10:23:13.520 回答
3

您也可以进行自我 JOIN，最快的一个将在很大程度上取决于您的表中有多少数据。

SELECT a.housing_id
FROM mytable a
INNER JOIN mytable b
ON a.housing_id = b.housing_id AND a.facility_id <> b.facility_id
WHERE a.facility_id = 4 AND b.facility_id = 7
于 2012-04-12T10:35:56.370 回答