mysql - 想在 SQL 列中使用数学，但它不是 INT

Question

我在“用户”表中有这一行：

id = 1; 
birthdate(date) = 1992-02-12; 
joined(int) = 2000;

我想创建这样的东西：

SELECT 
  CAST(birthdate as INT(4)) as birthyear, joined 
FROM 
  users 
WHERE 
  (birthyear - joined >= 20)

谁能给我一个提示/提示？提前致谢。

Answer 1

我想你想要这个功能year()：

select year(birthdate) as birthyear, joined
from users
where year(birthdate) - joined >= 20

Answer 2

您可以使用该YEAR()函数获取年份值。然后要获得您想要的结果，您可以使用以下内容：

select year(birthdate), joined
from users 
where (joined - year(birthdate)) >= 20

请参阅带有演示的 SQL Fiddle