Projection(ff): In relational algebra, a projection is a unary operation. The result of such projection is defined as the set obtained when the components Of the tuple R are restricted to the set {a1……an}. It discards (or excludes) the other attributes.

Selection( **σ**,): In relational algebra, a selection is a unary operation written as πaθb(R)πaθvor (R) where:

1. a and b are attribute names.

2. p is a binary operation in the set.

3. v is a value constant.

4. R is a relation.

The selection (R) selects all those tuples in R for which 9 holds between the a and the b

(b)

1. SELECT FROM EMPLOYEE ORDER BY DOJ DESC;

2. SELECT NAME, DESIGN FROM EMPLOYEE WHERE SGRADE – “S02” OR SGRADE = “SO3;

3. SELECT * FROM EMPLOYEE WHERE DOJ BETWEEN ’09-FEB-2006′ AND ’08- AUG -200%

4. INSERT INTO EMPLOYEE VALUES(109, “HARSH RAY”, “HEAD-IT.S02”, ’09-SEP- 2007′, ’21-APR-1983′);