Question on SQL Grouping - sql

Question

I am trying to achieve the following without using sub query.
For a funding, I would like to select the latest Letter created date and the ‘earliest worklist created since letter created’ date for a funding.
FundingId Leter (1, 1/1/2009 )(1, 5/5/2009) (1, 8/8/2009) (2, 3/3/2009)
FundingId WorkList (1, 5/5/2009 ) (1, 9/9/2009) (1, 10/10/2009) (2, 2/2/2009)
Expected Result -
FundingId Leter WorkList (1, 8/8/2009, 9/9/2009)
I wrote a query as follows. It has a bug. It will omit those FundingId for which the minimum WorkList date is less than latest Letter date (even though it has another worklist with greater than letter created date).
CREATE TABLE #Funding(
[Funding_ID] [int] IDENTITY(1,1) NOT NULL,
[Funding_No] [int] NOT NULL,
CONSTRAINT [PK_Center_Center_ID] PRIMARY KEY NONCLUSTERED ([Funding_ID] ASC)
) ON [PRIMARY]
CREATE TABLE #Letter(
[Letter_ID] [int] IDENTITY(1,1) NOT NULL,
[Funding_ID] [int] NOT NULL,
[CreatedDt] [SMALLDATETIME],
CONSTRAINT [PK_Letter_Letter_ID] PRIMARY KEY NONCLUSTERED ([Letter_ID] ASC)
) ON [PRIMARY]
CREATE TABLE #WorkList(
[WorkList_ID] [int] IDENTITY(1,1) NOT NULL,
[Funding_ID] [int] NOT NULL,
[CreatedDt] [SMALLDATETIME],
CONSTRAINT [PK_WorkList_WorkList_ID] PRIMARY KEY NONCLUSTERED ([WorkList_ID] ASC)
) ON [PRIMARY]
SELECT F.Funding_ID,
Funding_No,
MAX (L.CreatedDt),
MIN(W.CreatedDt)
FROM #Funding F
INNER JOIN #Letter L ON L.Funding_ID = F.Funding_ID
LEFT OUTER JOIN #WorkList W ON W.Funding_ID = F.Funding_ID
GROUP BY F.Funding_ID,Funding_No
HAVING MIN(W.CreatedDt) > MAX (L.CreatedDt)
How can I write a correct query without using subquery?
Please help
Thanks
Lijo

Answer 1

using derived tables is as good as it gets:
OP's tables:
CREATE TABLE #Funding(
[Funding_ID] [int] IDENTITY(1,1) NOT NULL,
[Funding_No] [int] NOT NULL,
CONSTRAINT [PK_Center_Center_ID] PRIMARY KEY NONCLUSTERED ([Funding_ID] ASC)
) ON [PRIMARY]
CREATE TABLE #Letter(
[Letter_ID] [int] IDENTITY(1,1) NOT NULL,
[Funding_ID] [int] NOT NULL,
[CreatedDt] [SMALLDATETIME],
CONSTRAINT [PK_Letter_Letter_ID] PRIMARY KEY NONCLUSTERED ([Letter_ID] ASC)
) ON [PRIMARY]
CREATE TABLE #WorkList(
[WorkList_ID] [int] IDENTITY(1,1) NOT NULL,
[Funding_ID] [int] NOT NULL,
[CreatedDt] [SMALLDATETIME],
CONSTRAINT [PK_WorkList_WorkList_ID] PRIMARY KEY NONCLUSTERED ([WorkList_ID] ASC)
) ON [PRIMARY]
OP's sample data:
INSERT INTO #Funding (Funding_No) VALUES (1)
INSERT INTO #Funding (Funding_No) VALUES (2)
INSERT INTO #Letter (Funding_ID,CreatedDt) VALUES (1,'1/1/2009')
INSERT INTO #Letter (Funding_ID,CreatedDt) VALUES (1,'5/5/2009')
INSERT INTO #Letter (Funding_ID,CreatedDt) VALUES (1,'8/8/2009')
INSERT INTO #Letter (Funding_ID,CreatedDt) VALUES (2,'3/3/2009')
INSERT INTO #WorkList (Funding_ID,CreatedDt) VALUES (1, '5/5/2009')
INSERT INTO #WorkList (Funding_ID,CreatedDt) VALUES (1, '9/9/2009')
INSERT INTO #WorkList (Funding_ID,CreatedDt) VALUES (1, '10/10/2009')
INSERT INTO #WorkList (Funding_ID,CreatedDt) VALUES (2, '2/2/2009')
The table CREATEs look like TSQL, but no version was given, so a CTE could have been used as well. However, this uses derived tables:
SELECT
dt.Funding_ID,LCreatedDt,MIN(CreatedDt) AS WCreatedDt
FROM (SELECT
f.Funding_Id,l.LCreatedDt
FROM #Funding f
LEFT OUTER JOIN (SELECT
Funding_ID,MAX(CreatedDt) AS LCreatedDt
FROM #Letter
GROUP BY Funding_ID
) l ON f.Funding_ID=l.Funding_ID
) dt
LEFT OUTER JOIN #WorkList w ON dt.Funding_ID=w.Funding_ID
WHERE w.CreatedDt>dt.LCreatedDt
GROUP BY dt.Funding_ID,LCreatedDt
OUTPUT:
Funding_ID LCreatedDt WCreatedDt
----------- ----------------------- -----------------------
1 2009-08-08 00:00:00 2009-09-09 00:00:00
(1 row(s) affected)
to preempt any people claiming that my query uses a subquery, read this article first on
Subquery Fundamentals: http://msdn.microsoft.com/en-us/library/aa213252(SQL.80).aspx
A subquery is a SELECT query that
returns a single value and is nested
inside a SELECT, INSERT, UPDATE, or
DELETE statement, or inside another
subquery. A subquery can be used
anywhere an expression is allowed.

Answer 2

Your question is How can I write a correct query without using subquery?
But you're not using a sub-query... so you already have your answer.