CONCAT'ing NULL fields

Question

I have a table with three fields, FirstName, LastName and Email.

Here\'s some dummy data:

FirstName | LastName | Email
Adam        West       adam@west.c         


        

Answer 1

Look at CONCAT_WS

For example:

CONCAT_WS('',NULL,"TEST STRING","TEST STRING 2")

Yields

TEST STRINGTEST STRING 2

This is easier than constructing IFNULL around everything. You can use an empty string as the separator.

Answer 2

SELECT ISNULL(FirstName,'')+ISNULL(LastName,'')+ISNULL(Email,'') as Vitals FROM MEMBERS

is recommended, but if you are really hooked on CONCAT, wrap it in {fn } and you can use the ODBC function like:

SELECT {fn CONCAT(ISNULL(FirstName,''), ISNULL(LastName,''), ISNULL(Email,''))} as Vitals FROM MEMBERS

If you need first<space>last but just last when first is null you can do this:

ISNULL(FirstName+' ','') + ISNULL(LastName,'')

I added the space on firstname which might be null -- that would mean the space would only survive if FirstName had a value.

To put them all together with a space between each:

RTRIM(ISNULL(Firstname+' ','') + ISNULL(LastName+' ','') + ISNULL(Email,''))

Answer 3

After observing the answers for this question, you may combine all of them into one simple solution

CONCAT_WS(',',
IF(NULLIF(FirstName, '') IS NULL, NULL, FirstName),
IF(NULLIF(LastName, '') IS NULL, NULL, usr_lastname),
IF(NULLIF(Email, '') IS NULL, NULL, Email))

So, in short we use CONCAT_WS to concatenate our fields and separate them with ,; and notice that NULL fields nor EMPTY wont concatenated

NULLIF will check if the field is NULL or EMPTY, a field that contains only spaces or is empty as well, ex: '', ' ') and the output will be either NULL or NOT NULL

IF Will out put the field if it's not NULL or EMPTY

Answer 4

You can always use the CONCAT_NULL_YIELDS_NULL setting..

just run SET CONCAT_NULL_YIELDS_NULL OFF and then all null concatenations will result in text and not null..

Answer 5

SQL Server does not have a CONCAT function.
(Update: Starting from MS SQL Server 2012 it was introduced CONCAT function)

In the default SQL Server behavior, NULLs propagate through an expression.

In SQL Server, one would write:

SELECT FirstName + LastName + Email as Vitals FROM MEMBERS

If you need to handle NULLs:

SELECT ISNULL(FirstName, '') + ISNULL(LastName, '') + ISNULL(Email, '') as Vitals FROM MEMBERS

Answer 6

In the case of MS Access

Option 1) SELECT (FirstName + " " + LastName + " " + Email) as Vitals FROM MEMBERS You will get blank result in the case of any field with null.

Option 2) SELECT (FirstName & " " & LastName & " " & Email) as Vitals FROM MEMBERS You will get Space in place of field with null.