Query optimization to yield computational results - sql

Question

Table Structure
It is very difficult to add tables in this posting, atleast I dont know. Tried using HTML table tags, but they wont appear good. Hence posting the table structure as an image.
Considering the 3 tables seen in the image, Projects, BC, Actual Spend, as an sample, I'm looking for an optimal query that returns the Reports as the result. As you can see, BC has some computation, Actual Spend has
SELECT ProjectId, Name, Budget
, (SELECT b.[BC] FROM [BC] b
WHERE b.[BC] IN
(SELECT SUM(mx.[BC]) FROM [BC] mx
WHERE ProjectId=p.ProjectId)) AS 'BC'
, (SELECT sp.[ActualSpendAmount] FROM [ActualSpend] sp
WHERE sp.[DateSpent] IN
(SELECT MAX(as.[DateSpent]) FROM [ActualSpend] as
WHERE ProjectId=p.ProjectId)) AS 'Actual Spend'
, t.[Budget] - ((SELECT b.[BC] FROM [BC] b
WHERE b.[BC] IN
(SELECT SUM(mx.[BC]) FROM [BC] mx
WHERE ProjectId=p.ProjectId))
+
(SELECT sp.[ActualSpendAmount] FROM [ActualSpend] sp
WHERE sp.[DateSpent] IN
(SELECT MAX(as.[DateSpent]) FROM [ActualSpend] as
WHERE ProjectId=p.ProjectId)))
FROM Projects p;
As you can see, the SELECT for BC, Actual Spend is run twice. I have several other tables like BC, Actual Spend, that yields some computation. Is there any way to optimize this. Even if I put them in a function, it would be the same, the function would need to be called more than once.
Is there a way to optimize this query.
Pasting the table structure below:
Projects Table:
ProjectId Name Budget
1 DeadRock 500000
2 HardRock 300000
BC Table: Actual Spend Table:
ProjectId BCId BC ApprovalDate ProjectId ActualSpendId ActualSpendAmount DateSpent
1 1 5000 2015/02/01 1 1 " 15000" " 2015/03/01"
1 2 3000 2015/03/10 1 2 " 33000" " 2015/05/12"
1 3 15000 2015/05/01 1 3 " 45000" " 2015/06/03"
1 4 5000 2015/07/01 1 4 " 75000" " 2015/07/11"
2 5 2000 2015/03/19 2 5 " 5000" " 2015/04/20"
2 6 6000 2015/05/20 2 6 " 19000" " 2015/05/29"
2 7 25000 2015/08/01 2 7 " 42000" " 2015/06/23"
2 8 " 85000" " 2015/07/15"
Report:
ProjectId Name Budget BC Actual Spend ETC
"1 " DeadRock 500,000 28,000 75,000 397,000 Budget-(BC+ActualSpend)
"2 " HardRock 300,000 " 33,000" 85,000 182,000 Budget-(BC+ActualSpend)

Answer 1

Based on your expected result your query is way too complicated (and will not run without errors).
Assuming your DBMS supports Windowed Aggregates:
SELECT p.ProjectId, p.NAME, p.Budget,
BC.BC,
act.ActualSpendAmount,
p.Budget - (BC.BC + act.ActualSpendAmount)
FROM Projects AS p
LEFT JOIN
( -- sum of BC per project
SELECT ProjectId, SUM(BC) AS BC
FROM BC
GROUP BY ProjectId
) AS BC
ON ProjectId=bc.ProjectId
JOIN
( -- latest amount per project
SELECT ProjectId, ActualSpendAmount,
ROW_NUMBER()
OVER (PARTITION BY ProjectId
ORDER BY DateSpent DESC) AS rn
FROM ActualSpend
) AS Act
ON Act.ProjectId=p.ProjectId
AND Act.rn = 1

Answer 2

Your correlated subquery for BC does not make any sense:
, (SELECT b.[BC] FROM [BC] b
WHERE b.[BC] IN
(SELECT SUM(mx.[BC]) FROM [BC] mx
WHERE ProjectId=p.ProjectId)) AS 'BC'
If we concentrate on projectID 1, you have the data here:
ProjectId BCId BC ApprovalDate
--------------------------------------------
1 1 5000 2015/02/01
1 2 3000 2015/03/10
1 3 15000 2015/05/01
1 4 5000 2015/07/01
Therefore this part of the query:
(SELECT SUM(mx.[BC]) FROM [BC] mx
WHERE ProjectId=p.ProjectId)
Will return 28,000. Then what you essentially have is:
, (SELECT b.[BC] FROM [BC] b
WHERE b.[BC] IN (28000)) AS 'BC'
Which will return null, unless there happens to be 1 and only 1 record in the table for any project with that particular amount in BC. If there is more than one you will get an error because more than one record is returned in the subquery.
I suspect, based on the report data you simply want the sum, so you can simply use:
SELECT p.ProjectId,
p.Name,
p.Budget
bc.BC
FROM Projects p
LEFT JOIN
( SELECT bc.ProjectID, SUM(bc.BC) AS bc
FROM BC
GROUP BY bc.ProjectID
) AS bc
ON bc.ProjectID = P.ProjectID;
To get the SUM of BC for each project.
I have made an assumption here that you are using SQL Server based on the use of square brackets for object names, and syntax in your previous questions. In which case I would use OUTER APPLY to get the latest actual spend row, giving a final query of:
SELECT p.ProjectId,
p.Name,
p.Budget
bc.BC,
sp.ActualSpendAmount AS [Actual Spend],
p.Budget - bc.BC + sp.ActualSpendAmount AS ETC
FROM Projects p
LEFT JOIN
( SELECT bc.ProjectID, SUM(bc.BC) AS bc
FROM BC
GROUP BY bc.ProjectID
) AS bc
ON bc.ProjectID = P.ProjectID
OUTER APPLY
( SELECT TOP 1 sp.ActualSpendAmount
FROM [ActualSpend] AS sp
WHERE sp.ProjectID = p.ProjectID
ORDER BY sp.DateSpent DESC
) AS sp;