Question

I have a table with four fields: ID auto increment, a string, and two integers.
I want to do something of the sort:

     select count(*) from table group by string

and then use the result to consolidate all counts which are larger than 1.

That is, take all rows which have count larger than 1, and replace all of these rows in the database (which have the same string) with a single row, ID does not matter, and the two integers are the sum over all rows of all of the rows with count larger than 1.

Is that possible using a few simple queries?

Thanks.

Answer 1

If you can stop the table from being updated by other users, then it’s pretty easy.

-- We're going to add records before deleting old ones, so keep track of which records are old.
DECLARE @OldMaxID INT
SELECT @OldMaxID = MAX(ID) FROM table

-- Combine duplicate records into new records
INSERT table (string, int1, int2)
SELECT string, SUM(int1), SUM(int2)
FROM table
GROUP BY string
HAVING COUNT(*) > 1

-- Delete records that were used to make combined records.
DELETE FROM table
WHERE ID <= @OldMaxID
GROUP BY string
HAVING COUNT(*) > 1