I needed to CONCAT a string in MySQL statement but it had null values which where wrecking the statement. Turns out you need to use CONACT_WS instead. This allows NULL values to be treated as empty strings as you would expect

# Fails
CONCAT('', 'foo', 'bar', NULL) = NULL

# Allows any null values
CONCAT_WS('', 'foo', 'bar', NULL) = 'foobar'

Related External Links:

• Makandra Cards - 825-mysql-concat-with-null-fields