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

You can use CASE statement

select Firstname 
      || case when Middlename <> '' Then '-'||Middlename  else '' END 
      || case when Surname<> '' Then '-'||Surname else '' END

As per your sample data I have check for empty string. To check NULL use Middlename IS NOT NULL instead of Middlename <> ''