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 的信息后我想数一下它们。有什么方法可以同时输入两个查询或解决我的问题吗？非常感谢

Answer 1

除非我遗漏了一些东西，如果您需要这些的计数，那么您可以使用:

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

如果您想返回 resident_info 和 count 中的所有数据，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