How to treat Null values in string concatenation

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Hello friends

I have sql statement that executes without exception but the result is not correct.

I concontenated fname, mname and and sname to form full_name but when I run the script, records with null values return Null for the full_name even though fname and sname exist for those records.

Please find my script below:

SQL

select  emp_id, 
   CASE mname WHEN NULL THEN  emp_id + ' - ' + upper(sname) COLLATE DATABASE_DEFAULT   + ',  ' + fname + N''   
   ELSE 
      emp_id + ' - ' + upper(sname) COLLATE DATABASE_DEFAULT + ',  ' + fname + '  ' +  mname end as full_name
from emp

Thanks in advance for your assistance

Posted 9-Feb-15 11:40am

noblepaulaziz

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2 solutions

Solution 2

Hi,

There are 2 ways to achieve the task.

1.) As mentioned in the solution by SA above using COALESCE(mname, '')
2.) Using ISNULL(mname, '') for example:

Select IsNull(ColName, '') As ColName From TableName

You can use any one of these methods to check for the null values in your script.

Thanks
Sisir Patro

Posted 9-Feb-15 17:37pm

Sisir Patro

Comments

deepakdynamite 10-Feb-15 6:56am

using COALESCE(mname, '') is better than IsNull.

jaket-cp 10-Feb-15 10:01am

Any examples on why coalesce is better than isnull?

deepakdynamite 10-Feb-15 22:34pm

For Eg: ISNULL(mname,FName)
In this case if Fname is also null and you want to check it, you have to code like this:

ISNULL(mname,ISNULL(FName,'Deepak'))

Where as if you are using Coalesce, you can directly write as
COALESCE(MNAME,FNAME,'Deepak'). You can provide n number of columns.

There is one more point for which you need to execute following code and check the difference.

DECLARE @NAME varchar(3) = null

SELECT ISNULL(@Name,'Deepak')
Select COALESCE(@Name,'Deepak')

jaket-cp 11-Feb-15 4:05am

Thanks for that.
So if multiple null checks are required then coalesce is the way to go.
Also done some reading up - isnull is not standard and coalesce is.

There is one down side, it is hard to spell :(
that gets me all the time :)

deepakdynamite 11-Feb-15 23:01pm

Right!!!!
Enjoy :)

[no name] 10-Feb-15 23:53pm

Yes, I do agree with your point. I had given the number of ways the solution can be achieved here. :)

noblepaulaziz 10-Feb-15 17:08pm

Thank you very much, I am most grateful

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Sergey Alexandrovich Kryukov · Accepted Answer · 2015-02-09T11:47:00

Solution 1

Check up your logic and consider using COALESCE(mname, '') to replace null with empty string.
See also, for example: http://stackoverflow.com/questions/8233746/concatenate-with-null-values-in-sql[^] (presently, a top answer).

—SA

Posted 9-Feb-15 11:47am

Sergey Alexandrovich Kryukov

Comments

noblepaulaziz 10-Feb-15 17:06pm

Thanks so much for solution

Sergey Alexandrovich Kryukov 10-Feb-15 17:28pm

You are very welcome.
Good luck, call again.
—SA