Question

我从Postgress开始，我需要使用四个id作为参数进行查询，这些可以是NULL，只有第一个是必需的，所以我试图获取包含每个id的数据的数据列表。如何在WHERE条件中检查id参数是否为非NULL。我会给你一个例子（不工作）

CREATE OR REPLACE FUNCTION sp_lock(
    IN p_id_1 character varying, 
    IN p_id_2 character varying DEFAULT NULL, 
    IN p_id_3 character varying DEFAULT NULL, 
    IN p_id_4 character varying DEFAULT NULL)
RETURNS SETOF character varying AS
$BODY$
BEGIN 
    UPDATE stock
    SET lock = 1
    FROM  (
      SELECT s.id
      FROM  stock s
      WHERE
        (ls.id = p_id_1 or p_id_1 is null) OR
        (ls.id = p_id_2 or p_id_2 is null) OR
        (ls.id = p_id_3 or p_id_3 is null) OR
        (ls.id = p_id_4 or p_id_4 is null) AND
        ls.lock = 0
      FOR UPDATE OF s
    ) i
    WHERE i.id = stock.id;

这里我需要首先检查，如果param是非NULL，然后连接到条件，使用OR exp。

Answer 1

您可以在where条件

中使用in operator

WHERE 
    s.id in (p_id_1, p_id_2, p_id_3, p_id_4) AND
    s.lock = 0;

是的，你不需要子查询：

UPDATE stock
SET lock = 1
WHERE
    id in (p_id_1, p_id_2, p_id_3, p_id_4) AND
    lock = 0;

完全相同但更快。

如何在Postgres函数中进行条件查询

1 个答案: