Question

我有这些表格：

tblCountry - country_number，country_name
tblDivingClub - club_number，country_number（FK）
tblDiver - diver_number，diver_name，startWorkingDate，endrtWorkingDate。
tblWorks_for -diver_number（FK），club_number（FK）

我需要编写一个没有视图或临时表的查询，这些查询会显示一些国家/地区：country_number，country_name，以及该国有25名或更多潜水员的潜水俱乐部数量（结束工作日期为IS NULL）。

这就是我到目前为止写的代码：

SELECT country_number, country_name,
(   SELECT count(distinct tblDivingClub.number) 
    FROM tblDivingClub 
    inner join tblCountry on tblDivingClub.country = tblCountry.country_number
     WHERE (
        (  SELECT count(tblWorks_for.diver_number) 
           FROM tblWorks_for 
           INNER JOIN tblDivingClub on  tblWorks_for.club_number = tblDivingClub.number 
           WHERE tblWorks_for.end_working_date IS null
                and tblDivingClub.number =   tblWorks_for.club_number) >25)
) as number_of_clubs
FROM tblCountry 
INNER JOIN tblDivingClub on tblCountry.country_number = tblDivingClub.country 
WHERE tblCountry.country_number = tblDivingClub.country 
GROUP by country_number, country_name

Answer 1

尝试这样的事情：

SELECT country_number, country_name, COUNT(DISTINCT club_number)
FROM
(
    SELECT tc.country_number, tc.country_name, tdc.club_number, count(*) as tot_cnt
    FROM tblCountry tc
    INNER JOIN tblDivingClub AS tdc   ON tdc.country_number = tc.country_number
    INNER JOIN tblWorks_for  AS tw    ON tw.club_number = tdc.club_number
    INNER JOIN tblDiver      AS td    ON td.diver_number = tw.diver_number
    WHERE endrtWorkingDate IS NULL
    GROUP BY tc.country_number, tc.country_name, tdc.club_number
    HAVING count(*) >= 25
) as der
GROUP BY country_number, country_name;

Answer 2

SQL预测聚合条件的需要是一件好事 - 如果你怀疑必须有一个更简单的方法，那你就是对的。我想你想要的东西：

SELECT country_number, country_name, count(distinct tblDivingClub.number) 
FROM tblCountry 
INNER JOIN tblDivingClub on tblCountry.country_number = tblDivingClub.country 
WHERE tblCountry.country_number = tblDivingClub.country 
GROUP by country_number, country_name
HAVING count(case when tblWorks_for.end_working_date IS null then 1 else null end) > 25

具有2个条件的SQL查询

2 个答案: