Expression to get other value if main value is empty string

[gdebrauwer]

The Coalesce expression allows you to get the first non-null value. But what if you want the first non-empty value? This PR adds an expression for that. I named it ifempty to make it similar to the ifnull database function (I don't know if adding an ifnull-expression is interesting, as an alternative for coalesce?)

new IfEmpty('name', 'email')

[tpetry]

The idea is interesting. But I am not sure what the behaviour should be.

how should it react to NULL, '', [], {}. I am not sure whether this opens up a nest of issues and the more verbose CASE WHEN idea from the discussions would fit better.

For the moment I try to stay as close to the SQL standard as possible because their behaviour is stated by someone else. Bit thanks for the idea.

If you want to add more, you can also first start a discussion to share your ideas 😉