CS430/630 Relational Algebra Lab   NAME: ________________
(3 points) 

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)

Relational Algebra 
sailors(sid, sname, rating, age)
reserves(sid, bid, day)
boats(bid, name, color)

Example 0:                                                                Example 1.
Find names of who have ratings at least 8.                 Find names of sailors who've reserved boat 103
Answers (various forms, all OK)      
                                                                                    π_sname(π_sid(σ_bid=103Reserves))⨝Sailors)
π_sname(σ_rating>=8 Sailors)                                            π_sname(σ_bid=103Reserves)⨝Sailors)
π_snameσ_rating>=8 Sailors                                               π_sname(σ_bid=103Reserves⨝Sailors)
                                                                                   Note wrong:  π_snameσ_bid=103Reserves⨝Sailors
                                                                                   (The precedence rule would apply the projection π_sname
                                                                                   to the result of  σ_bid=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'.