Help with a query - sql

Question

Based on the following table
ID Effort Name
-------------------------
1 1 A
2 1 A
3 8 A
4 10 B
5 4 B
6 1 B
7 10 C
8 3 C
9 30 C
I want to check if the total effort against a name is less than 40 then add a row with effort = 40 - (Total Effort) for the name. The ID of the new row can be anything. If the total effort is greater than 40 then trucate the data for one of the rows to make it 40.
So after applying the logic above table will be
ID Effort Name
-------------------------
1 1 A
2 1 A
3 8 A
10 30 A
4 10 B
5 4 B
6 1 B
11 25 B
7 10 C
8 3 C
9 27 C
I was thinking of opening a cursor, keeping a counter of the total effort, and based on the logic insert existing and new rows in another temporary table.
I am not sure if this is an efficient way to deal with this. I would like to learn if there is a better way.

Answer 1

I think the first part could be done this way:
INSERT INTO tbl(Effort, Name)
SELECT 40 - SUM(Effort), Name
FROM tbl
GROUP BY Name
HAVING SUM(Effort) < 40)
The second part is harder. Perhaps you could do something like this instead?
INSERT INTO tbl(Effort, Name)
SELECT 40 - SUM(Effort), Name
FROM tbl
GROUP BY Name
HAVING SUM(Effort) <> 40)
What this does is, rather than making changes to your actual data, adds a row with a negative number for the Name if the total effort is > 40 hours, or a positive value if it is < 40 hours. This seems much safer for your data integrity than messing with the original values.

Answer 2

In SQL Server 2008, this may be done with a single MERGE statement:
DECLARE #efforts TABLE (id INT NOT NULL PRIMARY KEY, effort INT NOT NULL, name CHAR(1))
INSERT
INTO #efforts
VALUES (1, 1, 'A'),
(2, 1, 'A'),
(3, 8, 'A'),
(4, 10, 'B'),
(5, 4, 'B'),
(6, 1, 'B'),
(7, 10, 'C'),
(8, 3, 'C'),
(9, 30, 'C'),
(10, 60, 'C')
SELECT *
FROM #efforts
ORDER BY
name, id
;WITH total AS
( SELECT *
FROM #efforts e
UNION ALL
SELECT ROW_NUMBER() OVER(ORDER BY name) +
(
SELECT MAX(id)
FROM #efforts
),
40 - SUM(effort),
name
FROM #efforts
GROUP BY
name
HAVING SUM(effort) < 40
),
source AS
(
SELECT *,
(
SELECT SUM(effort)
FROM total ep
WHERE ep.name = e.name
AND ep.id <= e.id
) AS ce,
COALESCE(
(
SELECT SUM(effort)
FROM total ep
WHERE ep.name = e.name
AND ep.id < e.id
), 0) AS cp
FROM total e
)
MERGE
INTO #efforts e
USING source s
ON e.id = s.id
WHEN MATCHED AND 40 BETWEEN cp AND ce THEN
UPDATE
SET e.effort = s.effort + 40 - ce
WHEN MATCHED AND cp > 40 THEN
DELETE
WHEN NOT MATCHED BY TARGET THEN
INSERT (id, effort, name)
VALUES (id, effort, name);
SELECT *
FROM #efforts
ORDER BY
name, id
In SQL Server 2005, you'll need two statements (in one transaction):
DECLARE #efforts TABLE (id INT NOT NULL PRIMARY KEY, effort INT NOT NULL, name CHAR(1))
INSERT
INTO #efforts
VALUES (1, 1, 'A')
INSERT
INTO #efforts
VALUES (2, 1, 'A')
INSERT
INTO #efforts
VALUES (3, 8, 'A')
INSERT
INTO #efforts
VALUES (4, 10, 'B')
INSERT
INTO #efforts
VALUES (5, 4, 'B')
INSERT
INTO #efforts
VALUES (6, 1, 'B')
INSERT
INTO #efforts
VALUES (7, 10, 'C')
INSERT
INTO #efforts
VALUES (8, 3, 'C')
INSERT
INTO #efforts
VALUES (9, 30, 'C')
INSERT
INTO #efforts
VALUES (10, 60, 'C')
;WITH total AS
(
SELECT *,
COALESCE(
(
SELECT SUM(effort)
FROM #efforts ep
WHERE ep.name = e.name
AND ep.id <= e.id
), 0) AS cp
FROM #efforts e
)
DELETE
FROM total
WHERE cp > 40
INSERT
INTO #efforts
SELECT (
SELECT MAX(id)
FROM #efforts
) +
ROW_NUMBER() OVER (ORDER BY name),
40 - SUM(effort),
name
FROM #efforts
GROUP BY
name
HAVING SUM(effort) < 40
SELECT *
FROM #efforts
ORDER BY
name, id

Answer 3

This will give you the names that need modify:
SELECT Name, SUM(Effort)
FROM Table
GROUP BY Name
HAVING SUM(Effort) < 40
Select this into a temp table, Add a column for 40 - SUM, then create an insert statement from that. Much better than a cursor.

Answer 4

This will do the first part:
Insert Into dbo.Test (Name, Effort)
Select t.Name, 40 - SUM(t.Effort)
From dbo.Test t
Group By t.Name
Having SUM(t.Effort) < 40
And this will do the second part:
Update a
Set a.Effort = a.Effort - b.AmountToDeduct
From dbo.Test a
Join (
Select t.Name, (40 - SUM(t.Effort)) as 'AmountToDeduct'
From dbo.Test t
Group By t.Name
Having SUM(t.Effort) > 40
)b on a.Name = b.Name
Where a.ID = (Select MAX(c.ID)
From dbo.Test c
Where c.Name = a.Name
)