Using EXISTS within a GROUP BY clause - sql

Question

Is it possible to do the following:
I have a table that looks like this:
declare #tran_TABLE TABLE(
EOMONTH DATE,
AccountNumber INT,
CLASSIFICATION_NAME VARCHAR(50),
Value Float
)
INSERT INTO #tran_TABLE VALUES('2018-11-30','123','cat1',10)
INSERT INTO #tran_TABLE VALUES('2018-11-30','123','cat1',15)
INSERT INTO #tran_TABLE VALUES('2018-11-30','123','cat1',5 )
INSERT INTO #tran_TABLE VALUES('2018-11-30','123','cat2',10)
INSERT INTO #tran_TABLE VALUES('2018-11-30','123','cat3',12)
INSERT INTO #tran_TABLE VALUES('2019-01-31','123','cat1',5 )
INSERT INTO #tran_TABLE VALUES('2019-01-31','123','cat2',10)
INSERT INTO #tran_TABLE VALUES('2019-01-31','123','cat2',15)
INSERT INTO #tran_TABLE VALUES('2019-01-31','123','cat3',5 )
INSERT INTO #tran_TABLE VALUES('2019-01-31','123','cat3',2 )
INSERT INTO #tran_TABLE VALUES('2019-03-31','123','cat1',15)
EOMONTH AccountNumber CLASSIFICATION_NAME Value
2018-11-30 123 cat1 10
2018-11-30 123 cat1 15
2018-11-30 123 cat1 5
2018-11-30 123 cat2 10
2018-11-30 123 cat3 12
2019-01-31 123 cat1 5
2019-01-31 123 cat2 10
2019-01-31 123 cat2 15
2019-01-31 123 cat3 5
2019-01-31 123 cat3 2
2019-03-31 123 cat1 15
I want to produce a result where it will check whether in each month, for each AccountNumber (just one in this case) there exists a CLASSIFICATION_NAME cat1, cat2, cat3.
If all 3 exist for the month, then return 1 but if any are missing return 0.
The result should look like:
EOMONTH AccountNumber CLASSIFICATION_NAME
2018-11-30 123 1
2019-01-31 123 1
2019-03-31 123 0
But I want to do it as compactly as possible, without first creating a table that groups everything by CLASSIFICATION_NAME, EOMONTH and AccountNumber and then selects from that table.
For example, in the pseudo code below, is it possible to use maybe an EXISTS statement to do the group by?
SELECT
EOMONTH
,AccountNumber
,CASE WHEN EXISTS (CLASSIFICATION_NAME = 'cat1' AND 'cat2' AND 'cat3') THEN 1 ELSE 0 end
,SUM(Value) AS totalSpend
FROM #tran_TABLE
GROUP BY
EOMONTH
,AccountNumber

Answer 1

You could emulate this behavior by counting the distinct classifications that answer this condition (per group):
SELECT
EOMONTH
,AccountNumber
,CASE COUNT(DISTINCT CASE WHEN classification_name IN ('cat1', 'cat2', 'cat3') THEN classification_name END)
WHEN 3 THEN 1
ELSE 0
END
,SUM(Value) AS totalSpend
FROM #tran_TABLE
GROUP BY
EOMONTH
,AccountNumber

Answer 2

Try this-
SELECT EOMONTH,
AccountNumber,
CASE
WHEN COUNT(DISTINCT CLASSIFICATION_NAME) = 3 THEN 1
ELSE 0
END CLASSIFICATION_NAME
FROM #tran_TABLE
GROUP BY EOMONTH,AccountNumber
Output is-
2018-11-30 123 1
2019-01-31 123 1
2019-03-31 123 0

Answer 3

Query like this. You can count distinct values.
When you count unique values then column 'Three_Unique_Cat'. When you count exactly 'cat1','cat2','cat3' then column 'Three_Cat1_Cat2_Cat3'
SELECT
EOMONTH, AccountNumber
,CASE WHEN
COUNT(DISTINCT CLASSIFICATION_NAME)=3 THEN 1
ELSE 0
END AS 'Three_Unique_Cat'
,CASE WHEN
COUNT(DISTINCT CASE WHEN CLASSIFICATION_NAME IN ('cat1','cat2','cat3')
THEN CLASSIFICATION_NAME ELSE NULL END)=3 THEN 1
ELSE 0
END AS 'Three_Cat1_Cat2_Cat3'
,SUM(Value) AS totalSpend
FROM #tran_TABLE
GROUP BY EOMONTH, AccountNumber
Output:
EOMONTH AccountNumber Three_Unique_Cat Three_Cat1_Cat2_Cat3 totalSpend
2018-11-30 123 1 1 52
2019-01-31 123 1 1 37
2019-03-31 123 0 0 15

Answer 4

It's easy, just as below:
select
EOMONTH,
AccountNumber,
case when count(distinct CLASSIFICATION_NAME) = 3 then 1 else 0 end as CLASSIFICATION_NAME
from
tran_TABLE
group by
EOMONTH,
AccountNumber