From: <>
Date: Tue, 22 Jul 2008 17:05:04 -0500
Message-ID: <>

Thanks, Ken

Thats a very good option

thank you

Gene Gurevich

             "Ken Naim"                                                    
             m>                                                         To 
             07/22/2008 04:48          <>            
             PM                                                         cc 
                                       RE: MERGE                           

Just use case statements in your merge command to determine if the value in the permanent and staging are defaults and adjust your logic accordingly. You can also use a where clause to filter out cases of all defaults, or to make sure atleast one non default exists.

If this is a high volume application, setting many columns to themselves in the case of non defaults can add a lot of load in which case the separate statements could perform better. This will depend on the ratio of defaults to non defaults, and whether indexes are present and enabled on these columns. Testing is key.

Merge into ...
Using ...
On ...
When matched
Then update

     set x.coll2= case when x.col12=0 then y.coll12 else coll12

Ken Naim

-----Original Message-----

From: [] On Behalf Of
Sent: Tuesday, July 22, 2008 4:12 PM
To: "" Subject: MERGE

Hi all:

My application team is doing the following. They have a table (col01, col02, col11, col12, col13) where col01 and col02 are primary key. They want to use the merge command to update/insert the data from a staging table which
has the same layout. One of the values in the col11/12/13 in the staging table is the new data, the other one or two are some default values. When they do merge command, these default data overwrite the data in the main table.
They are looking for a way to only modify the data in one of the columns (11/12/13) but not the others. If the staging table's col11 has the real data and col12 and col13 have default values, they only want to modify the col11 table in the main table. If the columns col11 and col13 in the stage table have the real data, they only want to modify
these columns in the main table without affecting the col12 etc. I don't think that one MERGE command will do that and that they would either need to provide all the correct data (no defaults) in the staging table or to create different versions of merge commands (updating different columns in the main table) and call them based on what data are written to the staging table.

Am I correct? Is there another (better) way to accomplish this?

thank you

Gene Gurevich


-- Received on Tue Jul 22 2008 - 17:05:04 CDT

Original text of this message