Question

我想根据以下需要在sql查询中使用if条件＆＃34;如果年份字段为空，则不计算年龄，如果已设置，则必须执行这是我的查询。问题出在哪里？请考虑这种情况＆＃39;如果有月份和日期，例如0000-03-12＆＃39;

SELECT id, name, birth_date, birth_time, 
            city_native, country_native, sex, 
            city_current, country_current, image,
            if(YEAR(birth_date)='','',YEAR(CURDATE()) - YEAR(birth_date) - 
              (RIGHT(CURDATE(),5) < RIGHT(birth_date,5)),'') AS age
        FROM birth_user u
        WHERE <condition>;

Answer 1

您可以使用IFNULL()检查birth_date是否为空

CASE WHEN IFNULL(birth_date,0)=0 THEN '' ELSE YEAR(CURDATE()) - YEAR(birth_date) END as age

Answer 2

如果您需要“如果它为空”，为什么要将它与零进行比较？

if(birth_date is null, 0, YEAR(CURDATE()) - ......) AS age

0有适当的“默认年龄”。

Answer 3

使用NULL而不是0000

SELECT id, name, birth_date, birth_time, 
city_native, country_native, sex, 
city_current, country_current, image,
if(birth_date is null,'',YEAR(CURDATE()) - YEAR(birth_date) - 
(RIGHT(CURDATE(),5) < RIGHT(birth_date,5)),'') AS age
FROM birth_user u
WHERE " . implode(' AND ', $where);

在sql查询中应用if条件

3 个答案: