mysql - 在使用 Min() 时是否要执行 Count()？

Question

下面的语句是从products表中获取所有不重复的ID。有什么方法可以获取此 sql 语句输出的总行数吗？

select min(product_id) from products 
where market_code = 'germany'
group by product_code

示例表数据:

product_id   market_code   product_code
   1            uk             AAA
   1            uk             AAA
   1            uk             AAA
   2           germany         BAA
   2           germany         BAA
   3            uk             BAA

谢谢

Answer 1

你可以简单地这样做:

SELECT COUNT(*)
FROM
(
    select min(product_id) from products 
    where market_code = 'germany'
    group by product_code
) AS t;