Question

给定父表'父'

╔═══════════╦══════════╗
║ PARENT_ID ║   NAME   ║
╠═══════════╬══════════╣
║         1 ║ bob      ║
║         2 ║ carol    ║
║         3 ║ stew     ║
╚═══════════╩══════════╝

和父和一个（这里未指定的）属性表之间的多对多关系表'rel'

╔═══════════╦═══════════╗
║ PARENT_ID ║  PROP_ID  ║
╠═══════════╬═══════════╣
║         1 ║         5 ║
║         1 ║         1 ║
║         2 ║         5 ║
║         2 ║         4 ║
║         2 ║         1 ║
║         3 ║         1 ║
║         3 ║         3 ║
╚═══════════╩═══════════╝

如何选择所有所有指定关系的父母？例如。使用样本数据，我如何找到同时具有属性5和1的父母？

编辑：同样的问题，但要求完全匹配： SQL Select only rows where exact multiple relationships exist

Answer 1

这称为 Relational Division

SELECT  a.name
FROM    parent a
        INNER JOIN rel b
            ON a.parent_ID = b.parent_ID
WHERE   b.prop_id IN (1,5)
GROUP BY a.name
HAVING COUNT(*) = 2

SQLFiddle Demo Link

更新1

如果prop_id对每个parent_id强制执行唯一约束，则此案例需要DISTINCT。

SELECT  a.name
FROM    parent a
        INNER JOIN rel b
            ON a.parent_ID = b.parent_ID
WHERE   b.prop_id IN (1,5)
GROUP BY a.name
HAVING COUNT(DISTINCT b.prop_id) = 2

Answer 2

为您的第一个表a命名，第二个表b

SELECT parent_id FROM prop b1 
WHERE prop_id=1 and 
EXISTS (SELECT parent_id FROM prop b2 
        WHERE b2.parent_id=b1.parent_id AND b2.prop_id=5)

Answer 3

我刚看到这个问题solution似乎适合这种情况：

 SELECT distinct parent_id
 FROM rel as T1
 INNER JOIN rel as T2
 ON T1.parent_id = T2.parent_id
 WHERE T1.prop_id = '1' and T2.prop_id = '5'

Answer 4

我已将您的表格写入CTE，如果您需要协助调整代码以便达到目的，请告知我们。

;WITH MyTable AS
(
    SELECT   parent_id = 1
            ,prop_id = 5    UNION ALL
    SELECT 1,1              UNION ALL
    SELECT 2,5              UNION ALL
    SELECT 2,4              UNION ALL
    SELECT 2,1              UNION ALL
    SELECT 3,1              UNION ALL
    SELECT 3,3              
)
,Eval AS
(
    SELECT   parent_id
            ,PropEval   = SUM(CASE WHEN prop_id IN (1,5) THEN 1 ELSE 0 END)
    FROM MyTable
    GROUP BY parent_id
)
SELECT parent_id
FROM Eval
WHERE PropEval = 2

SQL仅选择存在多个关系的行

4 个答案: