我需要创建一个人的数据库，人可以有一个或多个属性，每个人的属性都有一个特定的值，听起来很简单吧？好吧，继续阅读，因为问题有点不可能(5 天处理它:s)。

所以我创建了这 3 个表:

CREATE TABLE guy (
  id int(11),
  name varchar(255)
);

CREATE TABLE attribute (
  id int(11),
  name varchar(255)
);

-- each value references one guy and one attribute
CREATE TABLE _value (
  id int(11),
  guy_id int(11),
  attribute_id int(11),
  _value varchar(255)
);

使用此示例数据:

INSERT INTO attribute VALUES (1, 'age'), (2, 'dollars'), (3, 'candies');
INSERT INTO guy VALUES (1, 'John'), (2, 'Bob');
INSERT INTO _value VALUES (1, 1, 1, 12), (2, 1, 2, 15), (3, 1, 3, 3);
INSERT INTO _value VALUES (4, 2, 1, 15), (5, 2, 2, 20), (6, 2, 3, 6);

并创建这个查询:

SELECT g.name 'guy', a.name 'attribute', v._value 'value' 
FROM guy g 
JOIN _value v ON g.id = v.guy_id 
JOIN attribute a ON a.id = v.attribute_id;

这给了我这个结果:

+------+-----------+-------+
| guy  | attribute | value |
+------+-----------+-------+
| John | age       | 12    |
| John | dollars   | 15    |
| John | candies   | 3     |
| Bob  | age       | 15    |
| Bob  | dollars   | 20    |
| Bob  | candies   | 6     |
+------+-----------+-------+

这是真正的问题:

后来，我的老板告诉我他想使用尽可能多的条件来过滤数据，并且能够用“ands”和“ors”对这些条件进行分组，例如，他可能想做这个疯狂的条件:

获取年龄大于 10 岁、少于 18 美元、拥有多于 2 颗糖果且少于 10 颗糖果的人，但无论如何，也包括年龄恰好为 15 岁的人。 这将转化为这个过滤器:

-- should return both John and Bob
(age > 10 and dollars < 18 and candies > 2 and candies < 10) or (age = 15)

我创建过滤器没问题(我为此使用 jqgrid)，问题是属性不是列，而是行，因此我不知道如何将查询与过滤器混合，我尝试过这样的事情:

SELECT g.name 'guy', a.name 'attribute', v._value 'value' 
FROM guy g 
JOIN _value v ON g.id = v.guy_id 
JOIN attribute a ON a.id = v.attribute_id
GROUP BY guy
HAVING (
    (attribute = 'age' and value > 10) AND
    (attribute = 'dollars' and value < 18) AND
    (attribute = 'candies' and value > 2) AND
    (attribute = 'candies' and value < 10)
       )
OR
       (
     (attribute = 'age' and value = 15)
       )

但只返回 Bob :( 我应该得到 John 和 Bob。

那么，我应该如何混合使用过滤器和查询？

请记住，每个人拥有的属性数量对所有人来说都是相同的，但是可以随时添加更多属性和更多人，例如，如果我想添加“马里奥”这个人，我会这样做:

-- we insert the guy Mario
INSERT INTO guy VALUES (3, 'Mario');
-- with age = 5, dollars = 100 and candies = 1
INSERT INTO _value VALUES (7, 3, 1, 5), (8, 3, 2, 100), (9, 3, 3, 1);

如果我想创建“apples”属性，我会这样做:

-- we insert the attribute apples
INSERT INTO attribute VALUES (4, 'apples');
-- we create a value for each guy's new attribute, John as 7 apples, Bob has 3 and Mario has 8
INSERT INTO _value VALUES (10, 1, 4, 7), (11, 2, 4, 2), (12, 3, 4, 8);

现在我应该能够在我的查询中包含有关苹果的条件。

我希望我让自己明白了，谢谢你所有的时间:)

注意:也许如果有一种方法可以将每个人的所有属性都放在一行中，就像这样:

+------+-----------+-------+------+------------+--------+------+------------+--------+------+------------+--------+
| guy  | attribute | value | guy  | attribute  | value  | guy  | attribute  | value  | guy  | attribute  | value  |
+------+-----------+-------+------+------------+--------+------+------------+--------+------+------------+--------+
| John | age       |    12 | John | dollars    |     15 | John | candies    |      3 | John | apples     |      7 |
| Bob  | age       |    15 | Bob  | dollars    |     20 | Bob  | candies    |      6 | Bob  | apples     |      2 |
| Mario| age       |    5  | Mario| dollars    |     100| Mario| candies    |      1 | Mario| apples     |      8 |
+------+-----------+-------+------+------------+--------+------+------------+--------+------+------------+--------+

注意 2:@iim 建议(在这个问题中:How to search in grouped columns in MySQL? (also in Hibernate if possible))我可以为每个属性做一个自连接，是的，这可能会解决问题，但是当人们拥有大量属性时可能会出现性能问题(比如 30 个或更多)。

注意 3:我无法更改数据库架构 :(

最佳答案

像这样的东西怎么样？

SELECT g.name 'guy', a.name 'attribute', v._value 'value' 
FROM guy g 
JOIN _value v1 ON g.id = v1.guy_id 
  JOIN attribute a1 ON a1.id = v1.attribute_id
JOIN _value v2 ON g.id = v2.guy_id 
  JOIN attribute a2 ON a2.id = v2.attribute_id
JOIN _value v3 ON g.id = v3.guy_id 
  JOIN attribute a3 ON a3.id = v3.attribute_id
JOIN _value v4 ON g.id = v4.guy_id 
  JOIN attribute a4 ON a4.id = v4.attribute_id
JOIN _value v5 ON g.id = v5.guy_id 
  JOIN attribute a5 ON a5.id = v5.attribute_id
WHERE (
    (a1 = 'age' and v1 > 10) AND
    (a2 = 'dollars' and v2 < 18) AND
    (a3 = 'candies' and v3 > 2) AND
    (a4 = 'candies' and v4 < 10)
  ) OR (a5 = 'age' and v5 = 15)

编辑修复一些愚蠢的错误:

SELECT DISTINCT g.id, g.name 'guy'
FROM guy g 
JOIN _value v1 ON g.id = v1.guy_id 
  JOIN attribute a1 ON a1.id = v1.attribute_id
JOIN _value v2 ON g.id = v2.guy_id 
  JOIN attribute a2 ON a2.id = v2.attribute_id
JOIN _value v3 ON g.id = v3.guy_id 
  JOIN attribute a3 ON a3.id = v3.attribute_id
JOIN _value v4 ON g.id = v4.guy_id 
  JOIN attribute a4 ON a4.id = v4.attribute_id
JOIN _value v5 ON g.id = v5.guy_id 
  JOIN attribute a5 ON a5.id = v5.attribute_id
WHERE (
    (a1.name = 'age' and v1._value > 10) AND
    (a2.name = 'dollars' and v2._value < 18) AND
    (a3.name = 'candies' and v3._value > 2) AND
    (a4.name = 'candies' and v4._value < 10)
  ) OR (a5.name = 'age' and v5._value = 15)

具体来说，我忘记了 WHERE 子句中的字段名，只选择“guy”字段，并添加了 DISTINCT 以便每个人只获得一行。

关于mysql - 在 MySQL 中搜索分组列？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/7815323/