MySQL:SELECT IF()语句中的SELECT

Question

我能有这样的东西吗？

SELECT IF((SELECT COUNT(id) FROM table WHERE id = 1) = 0, 1, <nothing_to_happen>) AS Available

我的目标是选择这个:

+---------+
|Available|
+---------+
|1        |
+---------+

仅当此查询中未选择任何行时:

SELECT id FROM table WHERE id = 1

如果表中存在id = 1的行,我希望我的查询返回零行!那可能吗？

Answer 1

SELECT  1
FROM    dual
WHERE   NOT EXISTS
        (
        SELECT  NULL
        FROM    mytable
        WHERE   id = 1
        )