Learning Google BigQuery

Mastering transformation with User-Defined Functions

All of the functions listed so far in this chapter are built-in functions in BigQuery. They are fully supported by Google and were created to handle the common tasks most analysts have to deal with. With that said, from time to time, situations will arise where these common functions will not suffice. Usually, the analyst will need to create a very intricate query to deal with these situations. For this, Google has created UDFs (user-defined functions). UDFs allow users to temporarily create their own functions using the standard functions included in BigQuery. These functions can then be called throughout the rest of the query using only the name of the function as well as the input.