Update Fields only if there is no value

[clayt101]

I want to use an update query to update the values in a column, but only when there is no pre-existing value.

Will this query work:

UPDATE REGIS INNER JOIN Combination ON REGIS.WATER_WELL = Combination.DHH_ID SET Combination.DNR_STATUS = [REGIS].[WELL_STATU]
WHERE (([Combination].[DNR_STATUS] Is Null));

I am afraid to try it.

 

[Joe4]

I would recommend trying it on a test copy of your database, but I do see a potential problem:

UPDATE [COLOR=#ff0000][B]REGIS[/B][/COLOR]...

... SET [COLOR=#ff0000][B]Combination[/B][/COLOR].DNR_STATUS =...

So which table are you trying to update there? The REGIS table or the Combination table.
You see to have conflicting information there.

 

[james_lankford]

it looks ok to me

but you can always do this first

select REGIS.*,  Combination.* from REGIS INNER JOIN Combination ON REGIS.WATER_WELL = Combination.DHH_ID 
WHERE (([Combination].[DNR_STATUS] Is Null));

then you can see what will get updated

 

[clayt101]

Thanks for the help. I changed it to a select query, made a few modifications to the query, got the results that I wanted, and then ran the update query.
Thanks again!