sql - concatenate two database columns into one resultset column

Question

I use the following SQL to concatenate several database columns from one table into one column in the result set:

SELECT (field1 + '' + field2 + '' + field3) FROM table1

When one of the fields is null I got null result for the whole concatenation expression. How can I overcome this?

The database is MS SQL Server 2008. By the way, is this the best way to concatenate database columns? Is there any standard SQL doing this?

Answer 1

The SQL standard way of doing this would be:

SELECT COALESCE(field1, '') || COALESCE(field2, '') || COALESCE(field3, '') FROM table1

Example:

INSERT INTO table1 VALUES ('hello', null, 'world');
SELECT COALESCE(field1, '') || COALESCE(field2, '') || COALESCE(field3, '') FROM table1;

helloworld