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SQL-基于多行按条件选择

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SQL-基于多行按条件选择,sql,Sql,我有两张桌子： actions action_data action\u data属于actions，并具有以下列：action\u id，name，value 内容可能如下所示： SELECT DISTINCT actions.* FROM actions INNER JOIN action_data ON actions.id = action_data.action_id WHERE (action_data.name = 'planet'

我有两张桌子：

actions 
action_data

action\u data
属于actions，并具有以下列：
action\u id
，
name
，
value

内容可能如下所示：

SELECT DISTINCT 
    actions.* 
FROM 
    actions 
INNER JOIN 
    action_data ON actions.id = action_data.action_id 
WHERE 
    (action_data.name = 'planet' AND action_data.value = 'earth');

    declare @t TABLE(id int, name NVARCHAR(MAX), value NVARCHAR(MAX))

    INSERT INTO @t VALUES(1, 'planet', 'earth')
    INSERT INTO @t VALUES(1, 'object', 'spaceship_a')
    INSERT INTO @t VALUES(1, 'destination', 'mars')

    SELECT * FROM @t t1
    JOIN @t t2 ON t1.ID = t2.id
    WHERE t1.name = 'planet' AND t1.value = 'earth' 
    AND t2.name = 'object' AND t2.value = 'spaceship_a'

SELECT DISTINCT action_id
FROM action_data a1 JOIN action_data a2 USING(action_id)
WHERE 
    a1.name = 'planet' AND a1.value = 'earth' AND
    a2.name = 'object' AND a2.value = 'spaceship_a';

操作
：

id | 
-----
178| 
179|

操作\u数据
：

action_id |   name   | value
-------------------------------------
178       |  planet  | earth
178       |  object  | spaceship_a
179       |  planet  | earth
179       |  object  | building
现在我想选择动作，动作中有
planet=earth和object=spaceship\u a
数据

如何使用SQL实现这一点？如果您只有一个条件，它的工作方式如下：

SELECT DISTINCT 
    actions.* 
FROM 
    actions 
INNER JOIN 
    action_data ON actions.id = action_data.action_id 
WHERE 
    (action_data.name = 'planet' AND action_data.value = 'earth');

    declare @t TABLE(id int, name NVARCHAR(MAX), value NVARCHAR(MAX))

    INSERT INTO @t VALUES(1, 'planet', 'earth')
    INSERT INTO @t VALUES(1, 'object', 'spaceship_a')
    INSERT INTO @t VALUES(1, 'destination', 'mars')

    SELECT * FROM @t t1
    JOIN @t t2 ON t1.ID = t2.id
    WHERE t1.name = 'planet' AND t1.value = 'earth' 
    AND t2.name = 'object' AND t2.value = 'spaceship_a'

SELECT DISTINCT action_id
FROM action_data a1 JOIN action_data a2 USING(action_id)
WHERE 
    a1.name = 'planet' AND a1.value = 'earth' AND
    a2.name = 'object' AND a2.value = 'spaceship_a';
但是我需要来自
操作\u数据的两个或多个条件


有什么想法吗？
我使用
分组方法和
拥有方法来解决这些问题，因为这是一种非常通用的方法，适用于许多情况

就你而言：


select ad.action_id
from action_data ad
group by ad.action_id
having sum(case when name = 'planet' and value = 'earth' then 1 else 0 end) > 0 and
       sum(case when name = 'object' and value = 'spaceship_a' then 1 else 0 end) > 0;



having
子句中的每个条件统计匹配的行数。
>0
表示至少有一个


您可以
join
返回到
actions
表，以获取更多列（如果需要）。
如果条件数量不变，可以使用join，这将比使用总和和大小写分组快得多

如果有两个条件，您可以这样加入：


SELECT DISTINCT 
    actions.* 
FROM 
    actions 
INNER JOIN 
    action_data ON actions.id = action_data.action_id 
WHERE 
    (action_data.name = 'planet' AND action_data.value = 'earth');



    declare @t TABLE(id int, name NVARCHAR(MAX), value NVARCHAR(MAX))

    INSERT INTO @t VALUES(1, 'planet', 'earth')
    INSERT INTO @t VALUES(1, 'object', 'spaceship_a')
    INSERT INTO @t VALUES(1, 'destination', 'mars')

    SELECT * FROM @t t1
    JOIN @t t2 ON t1.ID = t2.id
    WHERE t1.name = 'planet' AND t1.value = 'earth' 
    AND t2.name = 'object' AND t2.value = 'spaceship_a'



SELECT DISTINCT action_id
FROM action_data a1 JOIN action_data a2 USING(action_id)
WHERE 
    a1.name = 'planet' AND a1.value = 'earth' AND
    a2.name = 'object' AND a2.value = 'spaceship_a';


当然，如果您有3个条件，则需要加入2次并添加新筛选器：


    SELECT * FROM @t t1
    JOIN @t t2 ON t1.ID = t2.id
    JOIN @t t3 ON t1.ID = t3.id
    WHERE t1.name = 'planet' AND t1.value = 'earth' 
    AND t2.name = 'object' AND t2.value = 'spaceship_a'
    AND t3.name = 'destination' AND t3.value = 'mars'



如果不需要特定于DBMS的语法，可以使用自动联接

我会这样做：


SELECT DISTINCT 
    actions.* 
FROM 
    actions 
INNER JOIN 
    action_data ON actions.id = action_data.action_id 
WHERE 
    (action_data.name = 'planet' AND action_data.value = 'earth');



    declare @t TABLE(id int, name NVARCHAR(MAX), value NVARCHAR(MAX))

    INSERT INTO @t VALUES(1, 'planet', 'earth')
    INSERT INTO @t VALUES(1, 'object', 'spaceship_a')
    INSERT INTO @t VALUES(1, 'destination', 'mars')

    SELECT * FROM @t t1
    JOIN @t t2 ON t1.ID = t2.id
    WHERE t1.name = 'planet' AND t1.value = 'earth' 
    AND t2.name = 'object' AND t2.value = 'spaceship_a'



SELECT DISTINCT action_id
FROM action_data a1 JOIN action_data a2 USING(action_id)
WHERE 
    a1.name = 'planet' AND a1.value = 'earth' AND
    a2.name = 'object' AND a2.value = 'spaceship_a';


这适用于2个条件，但可以扩展到3个或更多，使用
FROM
子句中数据表的多个副本以及相应的比较条件

在这种情况下，
a1
复制品用于第一种情况（行星-地球），而
a2
复制品用于第二种情况（物体-宇宙飞船a）


JOIN
允许我们在所有可能的组合中搜索匹配项（N行给出N^2个组合）

这可能不是最好、最有效的方法，但它是可靠的，不依赖于平台

演示如下：


mysql> select * from action_data;
+-----------+--------+-------------+
| action_id | name   | value       |
+-----------+--------+-------------+
|       178 | planet | earth       |
|       178 | object | spaceship_a |
|       179 | planet | earth       |
|       179 | object | building    |
+-----------+--------+-------------+
4 rows in set (0.02 sec)

mysql> SELECT DISTINCT action_id
    -> FROM action_data a1 JOIN action_data a2 USING (action_id)
    -> WHERE 
    ->     a1.name = 'planet' AND a1.value = 'earth' AND
    ->     a2.name = 'object' AND a2.value = 'spaceship_a';
+-----------+
| action_id |
+-----------+
|       178 |
+-----------+
1 row in set (0.00 sec)


还有一些选择：

1） 使用
存在


select *
from actions a
where exists (select 1 from action_data ad 
    where ad.action_id = a.id and ad.name = 'planet' and ad.value = 'earth')
and exists (select 1 from action_data ad 
    where ad.action_id = a.id and ad.name = 'object' and ad.value = 'spaceship_a');


2） 将
与


with q1 as (
    select action_id
    from action_data
    where name = 'planet' and value = 'earth'
),
q2 as (
    select action_id
    from action_data
    where name = 'object' and value = 'spaceship_a'
)
select *
from q1 inner join q2 on q1.action_id = q2.action_id;



因为您不知道要搜索的元数据的数量，所以我不建议使用未知/无限数量的
连接

改为使用组串联
：


select * from actions 
  join (
    select action_id,
      group_concat(name,'=',value order by name separator ',') as csv // MySQL
//    string_agg(name || '=' || value, ',' order by name) as csv // PostgreSQL
    from meta 
    where name in ('planet', 'object') 
    group by action_id
  ) meta 
  on actions.id = meta.action_id 
  where csv = 'object=building,planet=earth'



我很高兴听到SQL关于性能的建议，我想，如果要找到3+以上的值，性能会更好。
数据透视表会工作吗？以什么方式工作？我认为数据透视表不起作用如果你提前知道你的“名字”，数据透视表最终会看起来像一个普通的表：where planet=earth and object=spaceship\u a你在用哪个数据库管理系统？博士后？神谕