In SQL developer

Create an index based on balance from the customer table and call it balance_index.

How would you add PK to a table, without dropping it, for which no PK was declared with Create?

What is the purpose of the Oracle NVL function? Show an example where you use it.

In reporting total_sale by each REP including those who made no sale, which Table joins should be left join. And how to show zero in your report instead of null for reps with no sale.