How to achieve this output? - sql

Question

I have a table with data like this :
create table test (transferID int, customerNumber varchar(10), txnstatus int);
insert into test
values
(1, 1001, 1),
(2, 1001, 2),
(3, 1001, 1),
(4, 1002, 2),
(5, 1002, 1),
(6, 1002, 2),
(7, 1002, 1),
(8, 1002, 1),
(9, 1003, 2),
(10, 1003, 1),
(11, 1003, 1),
(12, 1003, 1),
(13, 1003, 1),
(14, ' ', 1),
(15, ' ', 2),
(16, NULL, 2);
and the excepted output is to display the fields with customer number, total number of txns for each customer, successfulTxns, failedTxns. Note that:
txnStatus 1 and 2 represent "success" and "fail" respectively.
customer number may be empty or NULL in some cases like last three rows
This is how I tried, but didn't get the excepted result
select customerNumber,
count(*) over (partition by 1) as TotalTxns,
case when txnstatus = 1 then count(txnstatus) else 0 end as successFulTrxn,
case when txnstatus = 2 then count(txnstatus) else 0 end as failedFulTrxn
from test
group by customerNumber, txnstatus
I expect the output to be:
CustNumber TotalTxns SuccessFulTxns FailedTxns
1001 3 2 1
1002 5 3 2
1003 5 4 1
2 1 1
NULL 1 0 1

Answer 1

Your logic is somewhat correct, you just need to put the CASE expression inside COUNT, not the other way round:
SELECT customerNumber
, COUNT(*) AS TotalTxns
, COUNT(CASE WHEN txnstatus = 1 THEN 1 END) AS SuccessFulTxns
, COUNT(CASE WHEN txnstatus = 2 THEN 1 END) AS FailedTxns
FROM test
GROUP BY customerNumber
Note that there is not such thing as empty INT. Empty strings/whitespace becomes 0 when converted to INT.

Answer 2

Instead of blank I inserted 0 as customerNumber is int. If you want the same order as expected result, If you need 0 and NULL at the end, you can use conditional orderby.
SELECT customerNumber
, COUNT(*) AS TotalTxns
, COUNT(CASE WHEN txnstatus = 1 THEN 1 END) AS successFulTrxn
, COUNT(CASE WHEN txnstatus = 2 THEN 1 END) AS failedFulTrxn
FROM test
GROUP BY customerNumber
ORDER BY CASE WHEN customerNumber IS NULL THEN 100000
WHEN customerNumber = 0 THEN 99999
ELSE customerNumber END

Answer 3

Conditional aggregation is the way to achieve this :
select customerNumber, count(transferID) as TotalTxns,
sum(case when txnstatus = 1 then 1 else 0 end) as successFulTrxn,
sum(case when txnstatus = 2 then 1 else 0 end) as failedFulTrxn
from test t
group by customerNumber;

Answer 4

If you have to do a grouping action on txnstatus, you obviously can't include that field in the grouping list.
Furthermore, you can't do the count inside the case, you have to do it outside, and you don't have to count the status, because if the status is '2', the result will be clearly uncorrect.
I would approach the problem as below.
select customerNumber, count(*) as TotalTxns,
sum(case when txnstatus = 1 then 1 else 0 end) as successFulTrxn,
sum(case when txnstatus = 2 then 1 else 0 end) as failedFulTrxn
from test
group by customerNumber
It gives to me the results you are looking for.