SQL using If Not Null on a Concatenation

Question

If I have the table

SELECT (Firstname || \'-\' || Middlename || \'-\' || Surname)  AS example_column
FROM example_table

This will

Answer 1

If you use Postgres, concat_ws() is what you are looking for:

SELECT concat_ws('-', Firstname, Middlename, Surname)  AS example_column
FROM example_table

SQLFiddle: http://sqlfiddle.com/#!15/9eecb7db59d16c80417c72d1e1f4fbf1/8812

To treat empty strings or strings that only contain spaces like NULL use nullif():

 SELECT concat_ws('-', Firstname, nullif(trim(Middlename), ''), Surname)  AS example_column
 FROM example_table