Multiple sub queries

问题

Is it possible to get the result as below from the same table date-wise records:

               Enrolled   Enrolled as Email  Enrolled as Text Deals Redeemed   
<First Date>   7          5                  2                6
<Next Date>    9          3                  6               14

Table structure look something like this:

Customer_id, field1, field2, responsecode, created_date

My current query is something like this:

Select 
   Created,
   Enroll = (Select COUNT(*) from tblCustomer where field1 <> '' group by created),
   Email = (Select COUNT(field1) from tblCustomer where field1 = 'E-mail' and field1     <>    '' group by created),
   Cell = (Select COUNT(*) from tblCustomer where field1 = 'Cell Phone' and field1 <> ''    group by created)
from tblCustomer 
group by created 
order by created

回答1:

Try:

select created_date,
       count(field1) Enrolled,
       count(case field1 when 'E-mail' then 1 end) Enrolled_as_Email,
       count(case field1 when 'Cell Phone' then 1 end) Enrolled_as_Cell,
       (Select COUNT(*)
        from tbl_TransactionDishout d
        where d.created = c.created_date and
              d.DishoutResponseCode = '0000') Deals_Redeemed
from tblCustomer c
group by created_date
order by created_date

回答2:

You don't want a COUNT(), but instead, a SUM( CASE/WHEN )

Select 
      Created, 
      count(*) TotalCnt,
      SUM( CASE WHEN Field1 = 'E-mail' then 1 else 0 END ) as EMailCnt,
      SUM( CASE WHEN Field1 = 'Cell Phone' then 1 else 0 END ) as CellCnt,
      SUM( CASE WHEN RedeamedCondition then 1 else 0 END ) as RedeamCnt
   from 
      tblCustomer  
   group by 
      created  
   order by 
      created 

Note... if created is a date/time you will need to have the group by based on the date portion ONLY of the "created", otherwise you would get different counts for every second... From another post, the following gets only the date portion of a date time by basically removing the hours:minutes:seconds portion

DATEADD(dd, 0, DATEDIFF(dd, 0, created)) 

or if that doesn't make sense, you could just do it by

datepart( yy, created) as GrpYear,
datepart( mm, created) as GrpMonth,
datepart( dd, created) as GrpDay,  ... rest of columns.....

来源：https://stackoverflow.com/questions/9497364/multiple-sub-queries