sql server语言 - 帮助使用case和group进行sql查询

Question

我有一个DB表，有一个日期和一个名为posneg的字段，值是'pos'， ' new '或'neg'。

我需要一个结果集，其中posneg值被添加，然后按日期分组。这样的

2010-10-03    5   (on that date it could be 12 pos, 5 neu and 7 neg)
2010-10-04    -3  (on that date maybe 10 pos, 2 neu and 13 neg)
...and so on

基本不重要，如你所见

Answer 1

SELECT
  date,
  posneg = SUM(
    CASE posneg
      WHEN 'pos' THEN 1
      WHEN 'neg' THEN -1
      ELSE 0
    END
  )
FROM atable
GROUP BY date

Answer 2

试试这个:

SELECT date, SUM(IF(posneg='pos',1,IF(posneg='neg',-1,0))) as total
FROM table GROUP BY date

Answer 3

with tab as(
select cast('12/12/2010' as smalldatetime) as dt, 'neg' as posneg 
union all
select cast('12/12/2010' as smalldatetime) as dt, 'pos' as posneg 
union all
select cast('12/12/2010' as smalldatetime) as dt, 'pos' as posneg 
union all
select cast('12/12/2010' as smalldatetime) as dt, 'pos' as posneg 
union all
select cast('12/15/2010' as smalldatetime) as dt, 'neg' as posneg 
union all
select cast('12/15/2010' as smalldatetime) as dt, 'neg' as posneg 
union all
select cast('12/15/2010' as smalldatetime) as dt, 'pos' as posneg
)
select dt,
sum(case when posneg='pos' then 1
         when posneg='neg' then -1
         else 0 end) as total
         from tab
         group by dt