Fill blank spaces in SQL table

Posted on 2009-06-30
Last Modified: 2012-08-14

I've got 2 columns fields in a table.

Field1 is awlays populated with data
Field 2 is mostly blank.

How do I populate field2 with data from field 1 if field 2 is empty, but only if field2 is empty?

Question by:edjones1

Assisted Solution

jwenting earned 100 total points
ID: 24744208
You want to do that on inserting a record or at a later date?
If the former, use a trigger on post-insert. See documentation for your database engine on how to implement triggers.

If the latter, a simple update query will do:
update mu_table set column2 = column1 where column2 is null;

commit that and you're done.

Assisted Solution

mnialon earned 100 total points
ID: 24744212
please try the following :

update t1 set field2 = field1 where field2 is null


LVL 59

Accepted Solution

Kevin Cross earned 200 total points
ID: 24744260
The above are correct.  However, if your field can be empty string '' instead of null, then just adjust like this:
update your_table_name

set field2 = field1

where isnull(field2, '') = ''

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LVL 18

Assisted Solution

brejk earned 100 total points
ID: 24744292
If blank means an empty string:

UPDATE YourTable
SET Field2 = Field1
WHERE Field2 = ''
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Expert Comment

ID: 24744295
@mwvisa1: If field2 is indexed the better would be:

update your_table_name
set field2 = field1
where field2 = '' or field2 is null
LVL 59

Expert Comment

by:Kevin Cross
ID: 24744317
I typically don't worry about performance on one time data cleanup activities, but you are correct that should always code to take advantage of indexes.  As a programmer, I like checking for NULL first then compare as string, BTW. :) habit!

LVL 59

Expert Comment

by:Kevin Cross
ID: 24744329
@brejk: And I should correct that, I don't worry on simple stuff like this. :) I would be in trouble if I ran anything too nasty on a production system...
LVL 18

Expert Comment

ID: 24744344
@mwvisa1: What a sad world would be without our habits ;-)
LVL 14

Expert Comment

ID: 24744901

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