Question

我有一个查询，我想显示车主和他们乘坐汽车，公共汽车或火车的次数。所以表格看起来应该是这样的;

Owner | Car | Bus | Train
-------------------------
Joe   | 1   | 2   | 4

这是我的查询;

Select owner, vehicle
From MyTable
    INNER JOIN(select  
  count(case when vehicle = 'Car' then 1 else 0 end) AS [Car],
  count(case when vehicle = 'Bus' then 1 else 0 end) AS [Bus],
  count(case when vehicle = 'Train' then 1 else 0 end) AS [Train]
from dbo.MyTable
where
     YEAR([CreatedOn]) = 2015
group by 
    vehicle)

我收到错误的语法错误

Answer 1

首先，使用sum()而不是count()。其次，您不需要子查询。第三，您需要按owner分组，而不是vehicle：

Select owner,
       sum(case when vehicle = 'Car' then 1 else 0 end) AS [Car],
       sum(case when vehicle = 'Bus' then 1 else 0 end) AS [Bus],
       sum(case when vehicle = 'Train' then 1 else 0 end) AS [Train]
From MyTable
where YEAR([CreatedOn]) = 2015
group by owner;

您可以使用count()，但它会计算非NULL值，因此会产生误导。例如，在您的情况下，条件逻辑被忽略。

编辑：

要完成剩下的工作，请使用相同的想法，只需更改条件：

       sum(case when vehicle not in ('Car', 'Bus', 'Train') then 1 else 0 end) AS Others

Answer 2

试试这个：

select owner
    ,count(case when vehicle = 'Car' then 1 end) as [Car]
    ,count(case when vehicle = 'Bus' then 1 end) as [Bus]
    ,count(case when vehicle = 'Train' then 1 end) as [Train]
from dbo.MyTable
where year([CreatedOn]) = 2015
group by owner

Answer 3

你不能使用ELSE 0，因为它会被计算在内。使用ELSE NULL或保留默认值。

Select owner,
     count(case when vehicle = 'Car' then 1 end) AS [Car],
     count(case when vehicle = 'Bus' then 1 end) AS [Bus],
     count(case when vehicle = 'Train' then 1 end) AS [Train],
     count(case when vehicle NOT IN ('Car', 'Bus', 'Train') 
                OR vehicle IS NULL THEN 1 END) AS [Others]
from dbo.MyTable
where YEAR([CreatedOn]) = 2015
group by owner;

Sql - 计数表查询错误

3 个答案: