Doing multiple group bys in the same SQL query

  • Hi Gurus,

    Here is a simple question:

    I have a table like this

    StockId TransactionId Amount

    MSFT     1     500

    MSFT     1     2500

    MSFT     2    1000

    CSCO     1    2500

    CSCO      1 2500

    AMZN     1   4000

    AMZN     2   5000

    AMZN      2  4000

    I want to get a result set with rows like these(basically group by stock id, avg amount for each of the transactionids) in a single sql statement.

    StockId  AvgAmountforTransaction id1 AvgAmountforTransactionid2

    MSFT     1500                                     1000

    CSCO     2500                                        0

    AMZN    4000                                         4500

     

    How do I do it in a single sql statement?

    Thanks in advance ! This is my first post - pls. let me know if this is not the right forum to ask about sql server sql issues.

  • if the number of transactions isn't too great.

    SELECT StockTransactions.StockID

    ,ISNULL(Tran1.AvgAmount,0) AS AvgAmountforTransactionid1 ,ISNULL(Tran2.AvgAmount,0) AS AvgAmountforTransactionid2

    from ( /*All distinct StockIDs to join*/

    select distinct StockID

    from test.dbo.StockTransactions StockTransactions

    ) StockTransactions

    left join /*Calculate transaction 1 */

    (SELECT StockID,AVG(amount) AvgAmount

    from test.dbo.StockTransactions

    where TransactionID=1

    group by StockID

    )Tran1 on StockTransactions.StockID=Tran1.StockID

    left join

    (SELECT StockID,AVG(amount) AvgAmount

    from test.dbo.StockTransactions

    where TransactionID=2

    group by StockID

    )Tran2 on StockTransactions.StockID=Tran2.StockID

  • drop table StockTransaction

    create table StockTransaction (

    StockId varchar(10),

    TransactionId int,

    Amount money)

    insert into StockTransaction values ('MSFT',1,500)

    insert into StockTransaction values ('MSFT',1,2500)

    insert into StockTransaction values ('MSFT',2,1000)

    insert into StockTransaction values ('CSCO',1,2500)

    insert into StockTransaction values ('CSCO',1,2500)

    insert into StockTransaction values ('AMZN',1,4000)

    insert into StockTransaction values ('AMZN',2,5000)

    insert into StockTransaction values ('AMZN',2,4000)

    select StockId,

     avg(case TransactionId when 1 then Amount else null end) Transaction1Average,

     avg(case TransactionId when 2 then Amount else null end) Transaction2Average

    from StockTransaction

    group by StockId

  • Thank you so much. This is amazingly concise.Awesome.

    Thanks again guys.

    Newbie

  • These examples do not cope with > 2 transactions, which I believe (from the other thread which you posted) is the requirement?

    The absence of evidence is not evidence of absence
    - Martin Rees
    The absence of consumable DDL, sample data and desired results is, however, evidence of the absence of my response
    - Phil Parkin

  • The field is actually transactiontype which only has 2 values. So this should work.

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