Relational Algebra and Basic SQL

See attachment for details.

A network intrusion refers to an activity where an attacker sends malicious packets to a victim to do malicious things (e.g. crash the victim machine, or gain root access of the victim machine). A network security company monitors the network and records the network intrusion events. For the purpose, it has the following two tables in its database. The table MACHINE contains information on attackers and on victims, and it has the following three fields: • hostname: the machine name of the attacker or the victim; e.g. andromeda.rutgers.edu. • ip: the IP address of the attacker or the victim; e.g. 9.9.9.9. • os: the operating system of the attacker or the victim; e.g. Linux, Windows. The primary key of the MACHINE table is ip. The table EVENT contains the attack information and it has the following three fields: • a-ip: the IP address of the attacker; e.g. 9.9.9.9. • v-ip: the IP address of the victim; e.g. 10.10.10.2. • date: the date the attack was performed; e.g. 3/7/2016. The primary key of the EVENT table includes all three fields