UNIX/Linux Commands we need to
use right away.
1. After logging onto users.cs.umb.edu or pe07.cs.umb.edu, give the command (using cat or more) to display your .forward file. This file contains your preferred email address, so email addressed to email@example.com will be sent to the right place.
2. Give the command to change directory from your login directory to your cs630 directory:
3. Give the command to display the filenames in the directory once there.
Find names of who have ratings at least 8. Find names of sailors who've reserved boat 103
Answers (various forms, all OK)
πsname(σrating>=8 Sailors) πsname(σbid=103Reserves)⨝Sailors)
πsnameσrating>=8 Sailors πsname(σbid=103Reserves⨝Sailors)
Note wrong: πsnameσbid=103Reserves⨝Sailors
(The precedence rule would apply the projection πsname
to the result of σbid=103Reserves, yielding an empty result.)
Problems for you to try:
1. Display all names and ratings of sailors of 2. Display sailors' snames and dates of all
age less than 20. reservations by that sailor.
3. Display sailors' sids, ages and names of all that
4. Find sids of sailors who reserved the boat
sailor's reserved boats. named 'Dory'.