函数中If语句的PGSQL错误

Question

我正在尝试为pgsql创建一个函数，如果报告厅中存在设备，我需要返回一个布尔值。我得到以下错误：

"ERROR: return type mismatch in function declared to return boolean"

"DETAIL: Function's final statement must be SELECT or INSERT/UPDATE/DELETE RETURNING."

CREATE FUNCTION hasProjector(int) RETURNS boolean AS $$
        DO
        $do$
        BEGIN
        IF EXISTS(SELECT * FROM LectureRoomEquipment WHERE LectureRoomID = $1 AND             EquipmentID = 1) THEN
            SELECT true AS hasProjector;
        ELSE
            SELECT false AS hasProjector;
        END IF;
        END
        $do$
    $$ LANGUAGE SQL;

有没有人建议我哪里做错了，以及我如何解决这个问题？谢谢。

Answer 1

您不需要plpgsql。使用纯SQL执行此操作

create function hasprojector(int) returns boolean as $$

    select exists (
        select *
        from lectureroomequipment
        where lectureroomid = $1 and equipmentid = 1
    );

$$ language sql;