Is there a SQL function to expand table?

Question

I vaguely remember there being a function that does this, but I think I may be going crazy.

Say I have a datatable, call it table1. It has three columns: column

Answer 1

Below is for BigQuery Standard SQL

I think below is close enough to what "got you crazy" o)

#standardSQL
SELECT copy.*
FROM `project.dataset.tabel1` t, UNNEST(FN.EXPAND(t, 3)) copy

To be able to do so, you can leverage recently announced support for persistent standard SQL UDFs, namely - you need to create FN.EXPAND() function as in below example (note: you need to have FN dataset in your project - or use existing dataset in which case you should use YOUR_DATASET.EXPAND() reference

#standardSQL
CREATE FUNCTION FN.EXPAND(s ANY TYPE, dups INT64) AS ( 
  ARRAY (
  SELECT s FROM UNNEST(GENERATE_ARRAY(1, dups)) 
  )
); 

Finally, if you don't want to create persistent UDF - you can use temp UDF as in below example

#standardSQL
CREATE TEMP FUNCTION EXPAND(s ANY TYPE, dups INT64) AS ( ARRAY(
  SELECT s FROM UNNEST(GENERATE_ARRAY(1, dups)) 
)); 
SELECT copy.*
FROM `project.dataset.tabel1` t, UNNEST(EXPAND(t, 3)) copy