Question

我有一张类似的表，

Class  City
01      xx
02      xx   
03      yy  
04      zz

我想要的结果是，（选择城市的类别和数量=城市= xx或城市= yy）

Class  Count
01      2 
02      2 
03      1
04      0

我无法理解的方法是将不匹配的行放入结果中。在这个例子中是Class 04的最后一行。

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Answer 1

您可以通过聚合来获取计数，然后加入结果：

select t.class, tc.cnt    
from table t join
     (select t.class, count(*) as cnt
      from table t
      group by class
     ) tc
     on tc.class = t.class;

Answer 2

尝试以下SQL：

SELECT t1.class, count(t2.class) AS COUNT FROM test t1
LEFT JOIN test t2 ON t1.city=t2.city AND t1.city in ('xx', 'yy')
GROUP BY t1.class, t1.city;

<强> SQL Fiddle

Answer 3

这可以帮到你：

create table #cc (class int ,city varchar(2))
insert into #cc values (1,'xx')
insert into #cc values (2,'xx')
insert into #cc values (3,'yy')
insert into #cc values (4,'zz')
--insert into #cc values (1,'xx')


select class,isnull(c.cnt,0)
from #cc cc
left join (select city ,count(city) as cnt 
            from #cc c where city in ('xx','yy') 
            group by city ) c on c.city = cc.city

Answer 4

这可能适合您的目的：

SELECT TableMain.Class，TableJoin.CityCount
来自TableMain JOIN（选择COUNT（*）作为CityCount，Class FROM TableMain GROUP BY City）TableJoin ON TableJoin.Class = TableMain.class;

在同一个表中加入两个sql语句

4 个答案: