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

In BigQuery, I would recommend a CROSS JOIN:

SELECT t1.*
FROM table1 CROSS JOIN
     (SELECT 1 as n UNION ALL SELECT 2 UNION ALL SELECT 3) n;

This can get cumbersome for lots of copies, but you can simplify this by generating the numbers:

SELECT t1.*
FROM table1 CROSS JOIN
     UNNEST(GENERATE_ARRAY(1, 3)) n

This creates an array with three elements and unnests it into rows.

In both these cases, you can include n in the SELECT to distinguish the copies.