Return first non-null value

Help
1

Hi all

Is there a native FQL function that will return the first non-null value? Similar to Coalesce in SQL? I have a few variables set using Let and I want to find the first that is non-nullable. I suppose I could put them all in an array and use a combination of Filter and Select but wondered if there was an easier way?

Cheers!

2

Nulls sort last, unless you set reverse: true: Data types - Fauna Documentation

Check the first value returned, if it is null, there are no non-null values to return, otherwise, there you go.

3

ok cool, I thought this would probably be the case. Was hoping there was something built in, but that’s fine, this will work just fine!

4

Sort comes from using sets, such as an index. That won’t help you use values in a Let expression. As you noted, you’d need to use Select and Filter:

> Let(
  {
    a: null,
    b: null,
    c: "a value!",
    d: null
  },
  Select(
    0,
    Filter(
      [Var("a"), Var("b"), Var("c"), Var("d")],
      Lambda("val", Not(IsNull(Var("val"))))
    )
  )
)
'a value!'

But if you can rework your query to use an index, you’ll be able to find the first non-null value for any number of values.