Why is my query inside of a case when failing? - sql-server

Question

I'm trying to run a SQL Server Case query and I'm running into an error. Let me try to explain why I'm doing what I'm doing, as well as what I'm looking for in the end result.
I have two Tables. 1 that has an opportunity ID (in this case A.ID) and the second table has accounts with one column I'm interested in (B.Q3ABM__C). What I'm asking SQL to do in this case when is that for every A.id that is null in in the B.Q3ABM__C colum give me a 1, and then again vice versa.
Why is this failing?
SELECT B.ID as Account_ID, B.FULL_ACCOUNT_ID__C, A.ID as Opportunity_ID,A.name, stagename,closedate,A.createddate,
OPPORTUNITY_PRODUCT__C,AMOUNT, B.Q3ABM__C, B.Drip_Campaign_Code__c,OPPORTUNITYTYPE_STRING__C,
CASE
WHEN (SELECT A.id FROM SF_OPPORTUNITY as a
LEFT JOIN SF_ACCOUNT as b on A.Accountid = b.ID where B.Q3ABM__C IS NULL) THEN 1
ELSE 0
END AS 'Does Not Exist in Q3DM',
CASE
WHEN (SELECT A.id FROM SF_OPPORTUNITY as a
LEFT JOIN SF_ACCOUNT as b on A.Accountid = b.ID where B.Q3ABM__C IS NOT NULL) THEN 1
ELSE 0
END AS 'Exists in Q3DM'
FROM SF_OPPORTUNITY as a
LEFT JOIN SF_ACCOUNT as b on a.ACCOUNTID = b.ID
WHERE A.createddate >= '7-1-2019'
AND CLOSEDATE <= '12-31-2019'
Thanks!

Answer 1

If you are selecting records in specific period, but you want to check for NULLs and NOT NULLs for all records, you can check for which ID there are NULL values. If NULL vales exists, then we can calculate the first Does Not Exist in Q3DM column, if not exists the second Exists in Q3DM:
WITH DataSource AS
(
SELECT DISTINCT A.id
FROM SF_OPPORTUNITY as a
LEFT JOIN SF_ACCOUNT as b
on A.Accountid = b.ID
where B.Q3ABM__C IS NULL
)
SELECT B.ID as Account_ID
,B.FULL_ACCOUNT_ID__C
,A.ID as Opportunity_ID
,A.name
,stagename
,closedate
,A.createddate
,OPPORTUNITY_PRODUCT__C
,AMOUNT
,B.Q3ABM__C
,B.Drip_Campaign_Code__c
,OPPORTUNITYTYPE_STRING__C
,CASE DS.Id IS NOT NULL THEN 1 ELSE 0 END 'Does Not Exist in Q3DM'
,CASE DS.Id IS NULL THEN 1 ELSE 0 END 'Exists in Q3DM'
FROM SF_OPPORTUNITY as a
LEFT JOIN SF_ACCOUNT as b
on a.ACCOUNTID = b.ID
LEFT JOIN DataSource DS
ON A.ACCOUNTID = DS.ID
WHERE A.createddate >= '7-1-2019'
AND CLOSEDATE <= '12-31-2019';
If you are interested only in the for the given period and checking the value for the current record only:
SELECT B.ID as Account_ID
,B.FULL_ACCOUNT_ID__C
,A.ID as Opportunity_ID
,A.name
,stagename
,closedate
,A.createddate
,OPPORTUNITY_PRODUCT__C
,AMOUNT
,B.Q3ABM__C
,B.Drip_Campaign_Code__c
,OPPORTUNITYTYPE_STRING__C
,CASE DS.Id IS NULL THEN 1 ELSE 0 END 'Does Not Exist in Q3DM'
,CASE DS.Id IS NOT NULL THEN 1 ELSE 0 END 'Exists in Q3DM'
FROM SF_OPPORTUNITY as a
LEFT JOIN SF_ACCOUNT as b
on a.ACCOUNTID = b.ID
LEFT JOIN DataSource DS
ON A.ACCOUNTID = DS.ID
WHERE A.createddate >= '7-1-2019'
AND CLOSEDATE <= '12-31-2019'

Answer 2

Try this (Use column in 'Select' and 'Where' clause as per your requirements):
SELECT A.*,B.* ,
CASE WHEN B.Q3ABM__C IS NULL THEN 1 ELSE 0 END AS 'DOES NOT EXISIT IN Q3DM',
CASE WHEN B.Q3ABM__C IS NOT NULL THEN 1 ELSE 0 END AS 'EXISITS IN Q3DM'
FROM PLS.SF_OPPORTUNITY A
FULL JOIN PLS.SF_ACCOUNT B ON A.ACCOUNTID=B.ID