如何在查询为空时显示某些内容？

Question

如果查询完成，我的代码显示“1”，查询为空时如何显示“0”。

SELECT  1 as 'access' 
FROM  `mytable` 
WHERE  `name` = 'Prophet Muhammad' and id = 1;

Answer 1

使用COUNT

SELECT  (COUNT(*) >= 1) as 'access' 
FROM    mytable
WHERE   name = 'Prophet Muhammad' and 
        id = 1;

• SQLFiddle Demo

Answer 2

你可以使用它，当查询返回至少一行时显示1，否则显示0：

SELECT EXISTS (SELECT Null
               FROM  `mytable` 
               WHERE  `name` = 'Prophet Muhammad' and id = 1) as Status