1

我有两个名为 country 和 city 的表，它们是关系表。

表结构：

Country : CountryID CountryName

City : CityID CountryID CityName

其中两个表都包含一些数据。我想要结果哪个国家的城市少于 3 个。

4

5 回答 5

1

试试这个

select c.CountryID
from country c
left join city ci on c.CountryID=ci.CountryID
group by c.CountryID
having COUNT(c.CountryID)<3
于 2013-10-01T06:41:13.047 回答
1 
 select c1.CountryName 
 from country c1 left join city c2 on c1.CountryID=c2.CountryID
 group by c2.CountryID,c1.CountryName,c1.CountryID having count(*)<3
于 2013-10-01T06:52:41.787 回答
0 
SELECT co.CountryID, co.CountryName, COUNT(ci.CityID) as NumberOfCities
FROM Country co
LEFT JOIN City ci
ON
co.CountryID = ci.CountryID
GROUP BY co.CountryID, co.CountryName
HAVING COUNT(ci.CityID) < 3
于 2013-10-01T07:02:56.570 回答
0 
SQL> select * from country;

CNID CNNAME
--- ----------
ind india
pak pakistan
usa amerika

SQL> select * from city;

      CTID CNID CTNAME
---------- --- ----------
        11 ind delhi
        22 ind mummbai
        55 pak lahore
        66 pak islamabad
        77 pak peshavar
       100 usa ny
       101 usa ams
       102 usa chi
       103 usa amaz

9 rows selected.


SQL> with ans as
  2  (select cn.cnname, cn.cnid, count(ctid)
  3  from country cn, city ct
  4  where cn.cnid = ct.cnid
  5  group by cn.cnid, cn.cnname
  6  having count(ctid)<3)
  7  select cnname from ans;

CNNAME
----------
india

SQL>
于 2015-09-22T18:11:45.407 回答
-2 
select * 
from country LEFT JOIN 
  (select CountryID, count(*) as cnt 
   from city 
   group by CountryID 
   having cnt<3) c ON country.CountryID =c.CountryID
于 2013-10-01T06:41:36.120 回答