error with an aggregate function but parses fine - sql-server

Question

I'm having trouble with this query
CREATE VIEW qryMonthlyFeesToCollectSummary1
AS
SELECT ContractID,
Round(Sum([CreditAmount] * ( ( 1
+ COALESCE((SELECT Max(MonthlyRate)
FROM tblCases
WHERE LEFT(CaseID, 4) = [ContractID] AND CaseStatus = 'Open Case'),
0.0199) ) / 30 ) * Exp(30 - 1)), 2) AS InterestCredit
FROM tblCredits
GROUP BY tblCredits.ContractID,
(SELECT Count(*)
FROM tblInterestPayments
WHERE ContractMainID = [ContractID]
AND ( PaymentDate IS NULL
OR ( PaymentDate IS NOT NULL
AND Bounced <> 0
AND RetrySuccessful IS NULL ) ))
HAVING (SELECT Count(*)
FROM tblInterestPayments
WHERE ContractMainID = [ContractID]
AND ( PaymentDate IS NULL
OR ( PaymentDate IS NOT NULL
AND Bounced <> 0
AND RetrySuccessful IS NULL ) )) = 0;
it errors out as shown below even though it parses fine. Please help! Thanks so much!
Msg 144, Level 15, State 1, Procedure qryMonthlyFeesToCollectSummary1,
Line 11 Cannot use an aggregate or a subquery in an expression used
for the group by list of a GROUP BY clause.
Msg 130, Level 15, State 1, Procedure qryMonthlyFeesToCollectSummary1,
Line 5 Cannot perform an aggregate function on an expression
containing an aggregate or a subquery.

Answer 1

I think this is what you are looking for:
CREATE VIEW qryMonthlyFeesToCollectSummary1
AS
SELECT ContractID,
Round(Sum([CreditAmount] * ( ( 1
+ COALESCE((SELECT Max(MonthlyRate)
FROM tblCases
WHERE LEFT(CaseID, 4) = [ContractID] AND CaseStatus = 'Open Case'),
0.0199) ) / 30 ) * Exp(30 - 1)), 2) AS InterestCredit
FROM tblCredits
WHERE (SELECT Count(*)
FROM tblInterestPayments
WHERE ContractMainID = tblCredits.[ContractID]
AND ( PaymentDate IS NULL
OR ( PaymentDate IS NOT NULL
AND Bounced <> 0
AND RetrySuccessful IS NULL ) )) = 0
GROUP BY tblCredits.ContractID;

Answer 2

I think I have got it right. Try to properly alias the table names and each column used in the query.
CREATE VIEW qryMonthlyFeesToCollectSummary1
AS
SELECT tblCredits.ContractID
, Round(Sum([CreditAmount] * ( ( 1
+ COALESCE(Max(MonthlyRate) , 0.0199) ) / 30 )
* Exp(30 - 1)), 2) AS InterestCredit
FROM tblCredits
INNER JOIN tblCases ON LEFT(CaseID, 4) = [ContractID]
AND CaseStatus = 'Open Case'
INNER JOIN tblInterestPayments ON ContractMainID = [ContractID]
WHERE PaymentDate IS NULL
OR ( PaymentDate IS NOT NULL
AND Bounced <> 0
AND RetrySuccessful IS NULL )
GROUP BY tblCredits.ContractID
HAVING Count(*) = 0;

Answer 3

You may try the following:
SELECT
Credits.ContractID,
ROUND(SUM(Credits.CreditAmount * ( ( 1 + COALESCE(Cases.MaxMonthlyRate,0.0199) ) / 30 ) * Exp(30 - 1)), 2) AS InterestCredit
FROM
tblCredits Credits
OUTER APPLY(
SELECT
Max(Cases.MonthlyRate) MaxMonthlyRate
FROM
tblCases Cases
WHERE
LEFT(Cases.CaseID, 4) = Credits.ContractID
AND Cases.CaseStatus = 'Open Case'
)Cases
WHERE
NOT EXISTS(
SELECT NULL
FROM tblInterestPayments Payments
WHERE
Payments.ContractMainID = Credits.ContractID
AND (
Payments.PaymentDate IS NULL
OR (
Payments.PaymentDate IS NOT NULL
AND Payments.Bounced <> 0
AND Payments.RetrySuccessful IS NULL
)
)
)
GROUP BY
Credits.ContractID
The errors you are experienced are encountered when you try to use an aggregate function (MAX, MIN, AVG, etc.) inside a subquery that is inside an expression that is already using an aggregate function. The remove them, I moved that subquery out of the select clause and into an outer apply. I used a Outer apply because you tagged the questions as SQL server and the subquery is performing an aggregate. In other databases you would use a left join.
Also, I moved the tblInterestPayments subquery into a NOT EXISTS clause. Since you are checking for the non existence of rows in the table matching a criteria, this makes more sense.

Answer 4

try something like:
CREATE VIEW qryMonthlyFeesToCollectSummary1
AS
SELECT
ContractID,
ROUND(SUM([CreditAmount] * ( ( 1 + COALESCE(max_monthlyRate, 0.0199) ) / 30 ) *
EXP(30 - 1)), 2) AS InterestCredit
FROM
tblCredits c LEFT OUTER JOIN
(SELECT
ContractMainID
FROM
tblInterestPayments
WHERE
PaymentDate IS NULL OR
( Bounced <> 0 AND RetrySuccessful IS NULL )) i ON
c.ContractID = i.ContractMainID LEFT OUTER JOIN
(SELECT
LEFT(CaseID, 4) AS left_caseID4,
MAX(MonthlyRate) AS max_monthlyRate
FROM
tblCases
WHERE
CaseStatus = 'Open Case'
GROUP BY
LEFT(caseid,4)) s ON
c.contractID = s.left_caseID4
WHERE
i.ContractMainID IS NULL
GROUP BY
ContractID