sql conditional insert if row doesn't already exist

Question

I\'m creating a sproc that will insert rows into a \'staging\' table with an insert into + subquery like so:

INSERT INTO myStagingTable
SELECT col1, col2, co         


        

Answer 1

INSERT
INTO    myStagingTable
SELECT  col1, col2, col3
FROM    myRealTable rt
WHERE   NOT EXISTS
        (
        SELECT  rt.col1, rt.col2, rt.col3
        INTERSECT
        SELECT  col1, col2, col3
        FROM    myStagingTable
        )

This will handle all duplicates (including NULL)

Note that is will insert the duplicates from the real table is any. Say if the real table contains

1 1 1
1 1 1

and the staging table contains

2 2 2

, both records with 1, 1, 1 will be inserted.

If you want to eliminate the duplicates on insert (so that only one instance of 1, 1, 1 is inserted), then just use this:

INSERT
INTO    myStagingTable
SELECT  col1, col2, col3
FROM    myRealTable
EXCEPT
SELECT  col1, col2, col3
FROM    myStagingTable