Question

How would I write the SQL statement
SELECT fname AS First_Name, lname AS Last_Name
FROM employee
WHERE salary BETWEEN 10000 AND 30000;

in relational algebraic syntax?

Answer 1

In relational algebra select statement of SQL is performed by π or project operation.

The where clause in SQL is equivalent to σ or select operation in relational algebra.

The rename operator is denoted by ρ symbol.

Hence, the required query in relational algebra is :

π _{First_Name, Last_Name} ( σ _{( salary >= 10000} ∧ _{salary <= 30000 )} ρ _{( First_Name/fname, Last_Name/lname )} ( employee ).