Database design discusion | Computer Science homework help

Part 1 Combining Tables

Please respond to BOTH of the following questions:

Question A

What is a join command? In addition, How can you combine two tables/views together? For instance one table contains 100 rows and the other one contains 200 rows, have exactly the same fields and you want to show a query with all data (300 rows).

Question B

Why can a “group by” or “order by” clause be expensive to process? What is the difference between a where and having clause?


Part 2 Peer Responses

Please respond to two peers.

Peer 1 Bill

The join clause does as it sounds, it will join two more tables in a relational database. I looked at some forums for suggestions, and one of the better answers I found in how to join the tables would be using the following syntax:

CREATEVIEW vw_combined AS


    FROM TABLE1 t1

    JOIN TABLE2 t2 ON t2.col = t1.col


Again, both tables need to have the same columns of data. The having clause is a limit on the results that are produced on the search. The where clause determines what row to be included on the select and what it is specifically looking for.


Peer 2 Ted’s responce to Bill

Bill, how would you combine the contents of two tables without a JOIN?