Concatenate multiple columns in SQL Server with NULL value

When we need to concatenate two columns simply we can use + sign and that is correct, but what if any of them is null, Will it return what we want, NO, it will return null. So let's discuss how we should concatenate two or more columns without creating extra space or extra comma problem. Let's say we have a customers table with following structure and data

alt text

Now suppose we have to bind a drop down on page so we need Customer id and FirstName + LastName so we will use

SELECT [CustomerID],  
[FirstName] + ' ' + [LastName] AS [CustomerName]
FROM Customers

It will work smooth because first name and last name both have some values no NULL column.

Now let's say, we have to use FirstName, MidleName and LastName as CustomerName, change our query to this one

SELECT [CustomerID],  
[FirstName] + ' ' + [MidleName] + ' ' + [LastName] AS [CustomerName]
FROM Customers

It will return

CustomerID  CustomerName
----------- ------------------
10001       Jamey Jo Durham
10002       NULL
10003       NULL
10004       NULL

Is there any mistake we made in our sql statement, no. It is because of the null value in Middle name, so how to fix it? We will check the column value by using ISNULL function and if it is null then we will use blank ('') [we don't want to go here in detail about the differences between blank and null because we are discussing here about concatenation of columns].

SELECT [CustomerID],  
IsNull([FirstName], '') + ' ' + IsNull([MidleName], '') 
   + ' ' + IsNull([LastName], '') AS [CustomerName]
FROM Customers
/* ---  Output  ---- */
CustomerID  CustomerName
----------- -----------------
10001       Jamey Jo Durham
10002       John  Smith
10003       Abhay  Singh
10004       Sunil  Kumar

It looks good but there is a problem, if you will see closely record 2,3 and 4, there are double spaces between first name and last name. It is not so bad, but suppose if we need ot use , in place of space then it will not look good. check the following example.

SELECT [CustomerID],  
[FirstName] + ' ' + [MidleName] + ' ' + [LastName] AS [CustomerName],
[Address1] + ', ' + [Address2] + ', '+ [City] 
  + ', '+ [State] + ', ' + [Country] + '-' + [Zip] AS [Address]
FROM Customers

/* -----------   See Output  ----------- */
CustomerID  CustomerName     Address
----------- ---------------- ----------------------------------------------
10001       Jamey Jo Durham  127 Park Avenue, Lane 10, Jersey City, NJ, USA-10234
10002       NULL             Lane 2, Friends Colony, New Delhi, DL, India-110025
10003       NULL             NULL
10004       NULL             NULL

Now let's use ISNULL function to check the null value and use blank if value is null, so new sql query will be

SELECT [CustomerID],  
IsNull([FirstName], '') + ' ' + IsNull([MidleName], '') + ' ' 
     + IsNull([LastName], '') AS [CustomerName],
IsNull([Address1], '') + ', ' + IsNull([Address2], '') + ', ' 
   + IsNull([City], '') + ', '+ IsNull([State], '') + ', ' 
   + IsNull([Country], '') + '-' + IsNull([Zip], '') AS [Address]

/* --- Output  ----*/
CustomerID  CustomerName     Address
----------- ---------------- ----------------------------------------------------
10001       Jamey Jo Durham  127 Park Avenue, Lane 10, Jersey City, NJ, USA-10234
10002       John  Smith      Lane 2, Friends Colony, New Delhi, DL, India-110025
10003       Abhay  Singh     A-123, T. Appartment, , , MB, -220345
10004       Sunil  Kumar     A-92 C, , New Delhi, , -
FROM Customers

In record 3 and 4 CustomerName have double space one for MiddleName and one for LastName. Similarly, Address column have extra commas, so how to fix them, do we need some logic to first check and then use space or commas. No, we will use Stuff and Coalesce to fix this problem, so change our above query to this one

SELECT [CustomerID],  
Stuff(
     Coalesce('' + [FirstName], '') 
   + Coalesce(' ' + [MidleName], '') 
   + Coalesce(' ' +[LastName], '')
   , 1, 1, '') AS [CustomerName],
Stuff(  
     Coalesce(', ' + [Address1], '') 
   + Coalesce(', ' + [Address2], '') 
   + Coalesce(', ' + [City], '') 
   + Coalesce(', ' + [State], '') 
   + Coalesce(', ' + [Country], '') 
   +Coalesce('-' + [Zip], '')
   , 1, 1, '') AS [Address]
FROM Customers

And here is the final output, is not it what we want

alt text

Ali Adravi Having 13+ years of experience in Microsoft Technologies (C#, ASP.Net, MVC and SQL Server). Worked with Metaoption LLC, for more than 9 years and still with the same company. Always ready to learn new technologies and tricks.
  • sql server
By Ali Adravi On 13 Feb, 13  Viewed: 8,860

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