I have a requirement as follows
1. I have three very large tables (A, B, C)
2. Table A and B are joined on a common key (a.id = b.id)
3. Table A and C and joined on a common key (a.id = c.id)
4. I want to write a query which unions the results of A->B and A->C.
5. I want to perform "group by" and "order by" on multiple columns from the joined data.
6. After grouping, we just sum, count on columns
Can I use a projection? or should I just create a new table which takes all required columns and unioned data and then perform grouping, sorting and sum/count on it.
I looked at pre-join projection.. but the documentation of 7.2 said pre-join is deprecated,
(page 56 https://my.vertica.com/docs/7.2.x/PDF/HP_Vertica_7.2.x_Complete_Documentation.pdf)
So will need your help in finding the right projection type or simply go for a new table.
