How do I use a merge statement to only replace null or blank fields

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I am trying to use the statement below to only update null or blank fields. Right now the way that it is set up is if it matches then up date the matched field whether or not its blank or null.

Merge into table1 as T
using [table] as S
on T.[Last Name] = S.[Last Name] and T.[First Name] = S.[First Name]

When Matched then 
Update Set T.[middle name] = S.[middle];

If there is a simple way to get this result I would be happy to see it.

What I have tried:

tried to use t.[middle name] is null, but its not exactly working the way I want it to.

Posted 8-Dec-17 19:27pm

Member 11856456

Updated 10-Dec-17 16:15pm

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Oshtri Deka 10-Dec-17 22:10pm

Please explain how does it not work?

1 solution

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Oshtri Deka · Accepted Answer · 2017-12-10T16:15:00

Solution 1

Try this:

SQL

Merge into table1 as T
using [table] as S
on T.[Last Name] = S.[Last Name] and T.[First Name] = S.[First Name]
and (T.[middle name] is null or TRIM(T.[middle name]) = '')
 
When Matched then 
Update Set T.[middle name] = S.[middle];

Posted 10-Dec-17 16:15pm

Oshtri Deka

Comments

CHill60 11-Dec-17 4:52am

I think I'd prefer and TRIM(ISNULL(T.[middle name],'')) = '' to having the OR - parentheses are often missed off when mixing ANDs and ORs

Oshtri Deka 12-Dec-17 5:39am

Valid point, your approach is more concise.
When it comes to parentheses, every coder should pay attention.