Concatenate with NULL values in SQL - sql

Question

Column1 Column2
------- -------
apple juice
water melon
banana
red berry
I have a table which has two columns. Column1 has a group of words and Column2 also has a group of words. I want to concatenate them with + operator without a space.
For instance: applejuice
The thing is, if there is a null value in the second column, i only want to have the first element as a result.
For instance: banana
Result
------
applejuice
watermelon
banana
redberry
However, when i use column1 + column2, it gives a NULL value if Comunm2 is NULL. I want to have "banana" as the result.

Answer 1

Use the COALESCE function to replace NULL values with an empty string.
SELECT Column1 + COALESCE(Column2, '') AS Result
FROM YourTable

Answer 2

A few posts I have made tagged MSSQL have been renamed to 'SQL' by a moderator. So I am assuming you are using MSSQL
COALESCE will return the FIRST non-null value.
SELECT COALESCE('a', NULL, 'c')
will only return 'a'
If you want Firstname + Lastname, where sometimes one or the other is NULL, use CONCAT. Concat adds the strings together and replaces NULLS with 0 length non-null value.
SELECT CONCAT('a', NULL, 'c')
will return 'ac'
If you want Fn space + middle name space + LN, combine concatinate with CONCAT:
SELECT CONCAT('a' + ' ', NULL + ' ', 'c')
Will return 'a c'.
The space after middlename (null) is eliminated with the + and NULL.
NULL + ' ' is null.
So in cases where Middlename or Firstname is null, you won't get extra unwanted spaces.

Answer 3

Standard SQL requires that string concatenation involving a NULL generates a NULL output, but that is written using the || operation:
SELECT a || b
FROM SomeTable;
The output will be null if either a or b or both contains a NULL.
Using + to concatenate strings indicates that you are using a DBMS-specific extension. The behaviour might be the same as the standard requires - indeed, that seems to be the gist of your question.
Some DBMS - notably Oracle - tend to treat null strings as equivalent to empty strings; then you can concatenate away merrily. However, that behaviour is not strictly standard-compliant if the || operator is used.
Consider using COALESCE or NVL or IFNULL or some similar function to map the NULL to an empty string before concatenating.

Answer 4

If you are using MySq, use ifnull(Column2, '')

Answer 5

I'm not certain what you're using as your database, but I would look for a "coalesce" function for your particular SQL dialect and use that.

Answer 6

The + sign for concatenation in TSQL will by default combine string + null to null as an unknown value.
You can do one of two things, you can change this variable for the session which controlls what Sql should do with Nulls
http://msdn.microsoft.com/en-us/library/ms176056.aspx
Or you can Coalesce each column to an empty string before concatenating.
COALESCE(Column1, '')
http://msdn.microsoft.com/en-us/library/ms190349.aspx

Answer 7

You can do a union:
(SELECT Column1 + Column2 FROM Table1 WHERE Column2 is not NULL)
UNION
(SELECT Column1 FROM Table1 WHERE Column2 is NULL);

Answer 8

You can use a case condition:
case when column_2 is not null
then concatenate
else column_1
end