Final challenge #1

In this challenge, we have a junk table.

For each junk_id we would like to add the following columns:

• even_num - row number from 2 to 2*n (n is the number of rows in the table) in jumps of 2: 2, 4, 6, 8, etc., ordered by junk_id
• num_piece - represents a group (using NTILE) that goes from 3 to 9 in jumps of 3: 3, 6, 9 (only 3 groups).
• avg_id - the average id of the current row and the 2 rows before it only in the same group
• piece_rank - dense rank of each group order by the avg_id