BigQuery Nested Table - if nested record do not exist?

Question

Have a straight question.

If the record is is null in SQL we use WHERE XXX is null

How about if nested records do not exist at all, like this:

WHERE XXX is empty???

What I would like to do? - Need to filter out records which do not have anything in OrderLines

Answer 1

Nested record is an array - to check if array is empty - I would use

WHERE ARRAY_LENGTH(OrderLines) = 0