SELECT E

$\_$

Fname, E

$\_$

Lname

FROM EMPLOYEEs

WHERE NOT EXISTS

$($

$$ SELECT

$1$

$$ FROM research

$$ WHERE EMPLOYEEs.Research

$\_$

ID

$=$

$$research$.$Research

$\_$

ID

$)$

;

for this query optimize it using tree:

a

$)$

$$Specify the initial canonical query tree that corresponds to the query.

b

$)$

$$Use query

$-$

processing steps to construct the suitable query tree for each SQL statement.

i

$)$

$$Remove duplicate projection

ii

$)$

$$Remove unnecessary group concatenation