计数同一表上具有不同值的记录可能没有SQL Server 2008

Question

我有一个清单表，其中包含一个条件，即新的，使用过的，其他条件，我正在查询一小部分该数据，并且所有记录集可能仅包含1个或所有条件。 我尝试使用case语句，但是如果未找到条件之一，则该条件没有返回，我需要它返回0

到目前为止，这是我尝试过的：

select(
case
    when new_used = 'N' then 'new'
    when new_used = 'U' then 'used'
    when new_used = 'O' then 'other'
    end
    )as conditions,
    count(*) as count
from myDB
where something = something
group by(
case 
    when New_Used = 'N' then 'new'
    when New_Used = 'U' then 'used'
    when New_Used = 'O' then 'other'
end
)

这将返回如下数据：

conditions | count
------------------
new           10
used          45

我试图使数据返回，如下所示：

conditions | count
------------------
new        | 10
used       | 45
other      | 0

提前致谢

Answer 1

;WITH constants(letter,word) AS 
(
  SELECT l,w FROM (VALUES('N','new'),('U','used'),('O','other')) AS x(l,w)
)
SELECT 
  conditions = c.word, 
  [count] = COUNT(x.new_used)
FROM constants AS c
LEFT OUTER JOIN dbo.myDB AS x
ON c.letter = x.new_used
AND something = something
GROUP BY c.word;

Answer 2

尝试这个 -

DECLARE @t TABLE (new_used CHAR(1))
INSERT INTO @t (new_used)
  SELECT t = 'N'
  UNION ALL 
  SELECT 'N'
  UNION ALL 
  SELECT 'U'

SELECT conditions, ISNULL(r.cnt, 0) AS [count]
FROM (
    VALUES('U', 'used'), ('N', 'new'), ('O', 'other')
) t(c, conditions)
LEFT JOIN (
    SELECT new_used, COUNT(1) AS cnt
    FROM @t
    --WHERE something = something
    GROUP BY new_used
) r ON r.new_used = t.c

在输出中-

new     2
used    1
other   0

Answer 3

您可以将其作为交叉表：

select
sum(case when new_used = 'N' then 1 else 0 end) as N,
sum(case when new_used = 'U' then 1 else 0 end) as U,
sum(case when new_used = 'O' then 1 else 0 end) as Other
from myDB
where something = something