mysql - MySQL以不同的方式使用Count

Question

我研究过这段代码：

select *,
  year(curdate())-year(dbirth) - (right(curdate(),5) < right(dbirth,5)) as age 
from       resident_info 
having age = 18;

但我想要的是在获得所有已经 18 的信息之后，我想计算它们。有什么办法可以同时输入两个查询或任何解决方案来解决我的问题？非常感谢

Answer 1

除非我遗漏了什么，如果你需要count这些，那么你可以使用：

select count(*)
from
(
  select *,
   year(curdate())-year(dbirth) - (right(curdate(),5) < right(dbirth,5)) as age 
  from       resident_info 
 having age = 18
) src

如果要从resident_info和中返回所有数据count，则可以使用CROSS JOIN：

select *, 
   year(curdate())-year(dbirth) - (right(curdate(),5) < right(dbirth,5)) as age,
   src.Total
from resident_info 
cross join
(
    select count(*) Total
    from
    (
        select year(curdate())-year(dbirth) - (right(curdate(),5) < right(dbirth,5)) as age 
        from  resident_info 
        having age = 18
    ) x
) src
having age = 18

Answer 2

这可能会有所帮助。

select temp.*,
   year(curdate())-year(dbirth) - (right(curdate(),5) < right(dbirth,5)) as age 
       FROM resident_info AS temp
       WHERE age = 18;