如何從聯接查詢中獲取一列的DISINCT值

Question

我正在查詢

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'

這給了我滿足條件的id_1，id_2和id_3的獨特組合。 查詢應如何獲取僅滿足所有條件的id_1的不同值。

我不發布表內容，因為它們具有大量列，並且此問題是查詢特定的。

Answer 1

您可以從查詢中刪除第二和第三字段。

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'