Question

I’m copying data from a table to an other one. I’m wondering what would be better to maintain data integrity and performance.

Steps :

1. copy data older than x days from log to archive
2. remove data from log if it exist in archive

From

INSERT INTO archive
    SELECT * FROM logs
    WHERE datediff(day, logs.timestamp, GetDate()) > @day

DELETE logsf FROM logs As logsf
    INNER JOIN archive as archivef ON logsf.uuid = archivef.uuid
    WHERE datediff(day, logsf.timestamp, GetDate()) > @jour        

To

INSERT INTO archive
    SELECT * FROM logs
    WHERE datediff(day, logs.timestamp, GetDate()) > @day
    AND NOT EXISTS (
        SELECT * FROM archive
        WHERE datediff(day, logs.timestamp, GetDate()) > @day
    )


DELETE logsf FROM logs As logsf
    INNER JOIN archive as archivef ON logsf.uuid = archivef.uuid
    WHERE datediff(day, logsf.timestamp, GetDate()) > @jour       

1. Is this a good thing to do to ensure you are not trying to insert already existing data in a table?
2. If my 2 original query are within a transaction, is my 2nd option pointless (and adding useless processing time)?

Which one would you use :

Insert if not exist + Delete if exist (independance)
or
Insert and delete if no error (transaction)
or
combine both

and why?

Answer 1

With SQL Server you can use the output clause to put the deleted items directly into the archive table:

DELETE logs
    OUTPUT deleted.* INTO archive
    WHERE datediff(day, timestamp, GetDate()) > @jour