$(1).$ Enter the following query in the query window $($do not execute it$)$:

select $*$

from table$\_$A

where $b\frac{?}{b}=ar(5000)$;

At the top of the query window, there is a horizontal bar with various icons, a part of which is

shown below:

Click the icon highlighted in green $($see above$).$ This icon is usually referred to as "EXPLAIN

plan icon or "EXPLAIN icon." Capture the screenshot of the visual execution plan and record the

query cost, which is shown on top of the execution plan.

$(2).$ Create an index on the column $,b$ of table$\_$A with the following sql statement:

create unique index table$\_$A$\_$b$\_$ix on table$\_$A$($b$)$;

Enter the same query again and the click the EXPLAIN plan icon again. Capture the screenshot

of the visual execution plan and record the query cost, which is shown on top of the execution

plan.

$(3).$ Compare the query cost from $(1)$ and the query cost from $(2).$ What conclusion can you

draw?