哪家商店注册的工人比实际能力多？

Question

哪家商店注册的工人比实际能力多？

我有三个表

Shop(shopid,shopname,shopcapacity) 
Workers(workerid,name,address) 
Registration(regid,workerid,shopid,fromdate,todate) 

我想下面的查询，它适用于具有比其身份登记的更多的工人一个店 - 但它不工作的每家商店，任何人都可以提出？

select shopname AS ShopName, 
shopcapacity AS ShopCapacity, 
count(r.shopid) AS RegisteredWorkers 
from shop f 
inner join registration r 
on f.shopid = r.shopid 
where f.shopcapacity < ANY (select count(shopid) 
from registration 
group by shopid) 
group by r.shopid; 

Answer 1

类似下面应该做的伎俩：

SELECT 
    shopname 
FROM 
    shop 
    LEFT OUTER JOIN registration reg on 
     shop.shopid = reg.shopid 
    LEFT OUTER JOIN workers on 
     reg.workerid = workers.workerid 
WHERE CURDATE() BETWEEN reg.fromdate and reg.todate 
HAVING count(distinct workerid) > shopcapacity 
GROUP BY shopname, shopcapacity 

我加了位与WHERE CURDATE()...，因为它看起来像你的registration表是对时间敏感的。

无论如何，这里的HAVING语句将检查是否当前注册工人的数量比shopcapacity更大。 GROUP BY确保数据库汇总在shopname和shopcapacity之间。