replacing null value

Question

If i am using

select coalesce(firstname, surname, petname) as column_name


select isnull(firstname, surname) as column_name

Where all return the first non-null column, if all the columns are null, how can I assign what to replace the null value in output with?

Typically as below for just checking for one column, I know I can insert value if null as below

 select coalesce(column_name, "value if null") as column_name

Also, can COALESCE and ISNULL be used interchangeably?

Thanks!

Answer 1

Presto does not have isnull function.

Presto does have coalesce syntax which takes arbitrary number of arguments; it's not a function, because it guarantees arguments are lazy-evaluated