Why to use "WHERE e.emp_no = 10001'?
What is the need of using the where clause in the union/union all.
1 answers ( 0 marked as helpful)
Hi Rafi!
Thanks for reaching out.
The WHERE clause in UNION/UNION ALL is used to filter rows from the individual queries before combining the results. This helps in selecting specific data subsets and improves performance by reducing the amount of data processed.
Hope this helps.
Best,
Tsvetelin