Question

假设我有一个对PostgreSQL数据库进行的SQL查询。如您所见，我在重复相同的子查询只是为了获得另一列。我坚信这是无效的。您认为执行sql查询的最佳方法是什么？

SELECT
    TABLE_A.COLUMN_1,
    TABLE_A.COLUMN_2,
    (
        SELECT
            TABLE_B.COLUMN_A,
        FROM 
            TABLE_B
        WHERE 
            TABLE_B.COLUMN_Z ILIKE CONCAT('%', TABLE_A.COLUMN_2, '%')
    ) AS COLUMN_3,
    (
        SELECT
            TABLE_B.COLUMN_B,
        FROM 
            TABLE_B
        WHERE 
            TABLE_B.COLUMN_Z ILIKE CONCAT('%', TABLE_A.COLUMN_2, '%')
    ) AS COLUMN_4,
FROM
    TABLE_A

Answer 1

使用加入

SELECT
    TABLE_A.COLUMN_1,
    TABLE_A.COLUMN_2, TABLE_B.COLUMN_A AS COLUMN_3, ABLE_B.COLUMN_B AS COLUMN_4
FROM
    TABLE_A 
JOIN
    TABLE_B ON TABLE_B.COLUMN_Z LIKE CONCAT('%', TABLE_A.COLUMN_2, '%')

Answer 2

使用横向连接：

SELECT a.COLUMN_1, a.COLUMN_2, b.*
FROM TABLE_A a LEFT JOIN LATERAL
     (SELECT b.COLUMN_A, b.COLUMN_B
      FROM TABLE_B b
      WHERE b.COLUMN_Z ILIKE CONCAT('%', a.COLUMN_2, '%')
    ) b
    ON 1=1;

如何正确地从PostgreSQL的子查询中获取多个列？

2 个答案: