Level-Up Your SQL WHERE Clause & Filter On This Complex Data Type

Don’t panic. Though I’ve tagged this piece with “Advanced SQL”, there is really only one function in this piece that, if you’ve worked with SQL even a little bit, you likely haven’t encountered.

Of course, if you’re reading a piece with the phrase “Advanced SQL” I have a few assumptions:

• You’re familiar with some more advanced data structures (ARRAY, STRUCT, etc.)
• You’ve used UNNEST() or ARRAY()
• You know how to use a subquery in the WHERE clause

For a primer on working with advanced data structures, including nested fields, I highly (and with a slight bias) recommend my previous writing on this topic.

• A SQL One-Liner To Master Your Pesky Nested Fields
• A No-Fear Introduction to Working with SQL Nested & Repeated Fields
• How To Create Nested Schemas in Python Using the Google BigQuery API

Once you’ve read that or trust that I’m doing my best to not confuse you, it’s time for a little STRUCT-ered fun (I acknowledge that pun is both a bit painful and inaccurate given we’re more focused on the ARRAY type).

Our end goal: To write a WHERE clause that filters rows for items contained in an ARRAY.

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