mysql - 如何从连接查询中获取一列的 DISTINCT 值

Question

我有一个类似的查询

SELECT DISTINCT table_1.id_1,
    table_1.id_2,
    table_1_id_3
FROM table_1
INNER JOIN table_2
    ON table_1.id_1 = table_2.id_1
        AND table_1.id_2 = table_2.id_2
INNER JOIN table_3
    ON table_2.id_1 = table_3.id_2
        AND table_2.id_2 = table_3.id_2
WHERE table_2.code = 'Y'
    AND table_2.site = 'N'
    AND table_3.code = 'Q'

这给了我满足条件的 id_1、id_2 和 id_3 的不同组合。查询应该如何获取仅匹配所有条件的 id_1 的不同值。

我不会发布表格内容，因为它们有大量列，而且这个问题是一个特定于查询的问题。

Answer 1

您可以从查询中删除第二个和第三个字段。

SELECT DISTINCT 
    table_1.id_1    
FROM table_1
INNER JOIN table_2
    ON table_1.id_1 = table_2.id_1
        AND table_1.id_2 = table_2.id_2
INNER JOIN table_3
    ON table_2.id_1 = table_3.id_2
        AND table_2.id_2 = table_3.id_2
WHERE table_2.code = 'Y'
    AND table_2.site = 'N'
    AND table_3.code = 'Q'