Postgresql：检查列是否同时等于多个值的最佳方法

Question

如果我想检查一列是否等于一个值或其他值，我写：

where col1 in (1, 4, 9);

但是如果我想同时检查一列是否等于这些值，我应该写：

where col1 = 1 and col1 = 4 and col1 = 9;

SQL 中是否有任何缩写形式，例如 in？

示例：

c1  |  c2
----------- 
1   |  1
1   |  2
1   |  3

Select 来自表名的 c1，其中 c2 = 1 且 c2 = 2；

在结果集中我想要1

Answer 1

PostgreSQL 已将 <operator> ALL 语法扩展到数组，因此您可以使用：

WHERE col1 = ALL (ARRAY[1, 4, 9])

Answer 2

关系划分：

CREATE TABLE ztable
        ( c1 integer not NULL
        , c2 integer not null
        , PRIMARY KEY (c1,c2)
        );
INSERT INTO ztable(c1,c2) values
 (1   ,  1) -- [c1=1] should match
,(1   ,  2)
,(1   ,  3)
,(2   ,  3) -- [c1=2] should NOT match
,(2   ,  4)
        ;

WITH musthave (val) AS (VALUES (1), (2))
SELECT distinct c1
FROM ztable zt
WHERE NOT EXISTS ( -- we DONT WANT the records
        SELECT * FROM musthave mh
        WHERE NOT EXISTS ( -- for which one of the musthaves is missing
                SELECT * FROM ztable nx
                WHERE nx.c1 = zt.c1
                AND nx.c2 = mh.val
                )
        )
        ;

-- 对于较小的问题（有限的必须具备的值）你可以这样做：

SELECT distinct c1
FROM ztable zt
WHERE zt.c2 = 1
AND EXISTS (
        SELECT *
        FROM ztable t2
        WHERE t2.c1 = zt.c1
        AND t2.c2 = 2
        );

-- 还有另一种方法，计算匹配的 c2 值：

SELECT DISTINCT zt.c1
FROM ztable zt
JOIN    (
        SELECT c1, COUNT(DISTINCT c2) AS cnt
        FROM ztable t2
        WHERE t2.c2 IN (1, 2)
        GROUP BY c1
        ) zzz ON zzz.c1= zt.c1
WHERE zzz.cnt = 2
    ;

Postgresql：检查列是否同时等于多个值的最佳方法

Postgresql: the best way to check if column is equal to multiple values simultaneously

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postgresql

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