UNIX/Linux Commands we need to use right away.
1. Give the command to change directory from your login directory to your cs630 directory:
2. Give the command to display the filenames in the directory once there.
3. Give the command to change directory back to your login directory from your cs630 directory.
4. Give the command to use sqlplus for your Oracle account (sqlplus user/pw@//dbs3.cs.umb.edu/dbs3)
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'.