在多对多关系中查找具有完全匹配的记录

Question

我有三个看起来像这样的表:

PROD

Prod_ID|Desc
------------
P1|Foo1
P2|Foo2
P3|Foo3
P4|Foo4
...

内存

Ram_ID|Desc
------------
R1|Bar1
R2|Bar2
R3|Bar3
R4|Bar4
...

PROD_RAM

Prod_ID|Ram_ID
------------
P1|R1
P2|R2
P3|R1
P3|R2
P3|R3
P4|R3
P5|R1
P5|R2
...

在PROD和RAM之间,PROD_RAM表描述了多对多关系.

给定一个Ram_ID像(R1,R3)我想要找到的所有PROD具有给定集合中的一个或全部的RAM集合.

给定(R1,R3)应该返回例如P1,P4和P5; P3不应该被返回,因为有R1和R3也R2.

什么是让所有的最快的查询PROD具有正是ONE或全部的Ram_ID给定的RAM一组？

编辑:
该PROD_RAM表可能包含大于1-> 3的关系,因此,"硬编码"检查count = 1 OR = 2不是一个可行的解决方案.

Answer 1

您可以尝试提高速度的另一种解决方案是这样的

;WITH CANDIDATES AS (
    SELECT  pr1.Prod_ID
            , pr2.Ram_ID
    FROM    PROD_RAM pr1
            INNER JOIN PROD_RAM pr2 ON pr2.Prod_ID = pr1.Prod_ID
    WHERE   pr1.Ram_ID IN ('R1', 'R3')
)
SELECT  *
FROM    CANDIDATES
WHERE   CANDIDATES.Prod_ID NOT IN (
            SELECT  Prod_ID
            FROM    CANDIDATES
            WHERE   Ram_ID NOT IN ('R1', 'R3')
        )           

或者如果您不喜欢重复设定的条件

;WITH SUBSET (Ram_ID) AS (
    SELECT  'R1'
    UNION ALL SELECT 'R3'
)   
, CANDIDATES AS (
    SELECT  pr1.Prod_ID
            , pr2.Ram_ID
    FROM    PROD_RAM pr1
            INNER JOIN PROD_RAM pr2 ON pr2.Prod_ID = pr1.Prod_ID
            INNER JOIN SUBSET s ON s.Ram_ID = pr1.Ram_ID    
)
, EXCLUDES AS (
    SELECT  Prod_ID
    FROM    CANDIDATES
            LEFT OUTER JOIN SUBSET s ON s.Ram_ID = CANDIDATES.Ram_ID
    WHERE   s.Ram_ID IS NULL
)
SELECT  *
FROM    CANDIDATES
        LEFT OUTER JOIN EXCLUDES ON EXCLUDES.Prod_ID = CANDIDATES.Prod_ID
WHERE   EXCLUDES.Prod_ID IS NULL