Question

我在postgresql中创建一个函数，它将执行以下操作：

CREATE OR REPLACE FUNCTION check_label_id_exist(_labelid integer, OUT result text) AS
$BODY$
DECLARE
BEGIN
    SELECT pkid FROM table_1 WHERE label_id = _labelid;
    IF FOUND THEN
    result := 'true';
    RETURN;
    IF NOT FOUND THEN
    SELECT pkid FROM table_2 WHERE label_id = _labelid;
    IF FOUND THEN
    result := 'true';
    RETURN;
    IF NOT FOUND THEN
    SELECT pkid FROM table_3 WHERE label_id = _labelid;
    IF FOUND THEN
    result := 'true';
    RETURN;
    IF NOT FOUND THEN
    result := 'false';

    RETURN;
END
$BODY$ language plpgsql;

此处该函数首先在table_1中查找数据。如果没有数据，那么它将转到下一个表，依此类推。如果任何表有数据，它将破坏条件并返回true，否则最终将返回false。我认为我在这里写的代码不正确。请帮助实现我的目标。

Answer 1

这可能是一种更简单的方法，可以用较少的代码来完成您正在尝试的操作。

CREATE OR REPLACE FUNCTION check_label_id_exist(_labelid integer, OUT result text) as

$BODY$
 BEGIN

    IF EXISTS(SELECT 1 FROM table_1 WHERE label_id = _labelid limit 1) THEN

        result := 'true';

    ELSEIF EXISTS(SELECT 1 FROM table_2 WHERE label_id = _labelid limit 1) THEN

        result := 'true';

    ELSEIF EXISTS(SELECT 1 from table_3 WHERE label_id = _labelid limit 1) THEN

        result := 'true';

    ELSE

        result := 'false';
    END IF;

    RETURN;
END
$BODY$ language plpgsql;

Answer 2

CREATE OR REPLACE FUNCTION check_label_id_exist(_labelid integer,
    OUT result text) AS
$BODY$
DECLARE
BEGIN
    SELECT pkid FROM table_1 WHERE label_id = _labelid;
    IF FOUND THEN
        result := 'true';
        RETURN;
    end if;

    SELECT pkid FROM table_2 WHERE label_id = _labelid;
    IF FOUND THEN
        result := 'true';
        RETURN;
    end if;

    SELECT pkid FROM table_3 WHERE label_id = _labelid;
    IF FOUND THEN
        result := 'true';
        RETURN;
    end if;
    result := 'false';
    RETURN;
END
$BODY$ language plpgsql;

postgresql创建具有多个IF ELSE条件的函数

2 个答案: