why should database tables be linked? please answer urgently!?

Question

I have a GCSE ICT test tomorrow.

I did a practice paper -- the question I'm struggling to understand is: "Give one reason why the video store should link tables together" in a database.

The answers were: "Avoids duplication of data/redundant data within tables, Less data entry so less time and less likely to make errors, Can produce report/select fields/take fields from each of the tables."

I don't understand this! Why would you need to enter data multiple times if you aren't intending to link the tables? Why does linking tables prevent entering data multiple times?

THANKS SO MUCH!

Answer 1

If you do not link the tables your example of a video store would need to enter the movie title mult. times for each video.



We know that most video stores will have a popular movie many times, so they enter the title once (this avoids spelling errors that can occur and saves keying), now they link each movie to that title.



example: The movie "Serendipity" the video store has 5 copies to rent.



They enter the title once and check spelling to insure it's correct in the MovieTable.

Now they enter each movie DVD into the RentTable, each DVD has a number seq. from 1 to 5. The RentTable is linked to the MovieTable, so they do not need to enter the title. All forms and reports will get the title information from the MovieTable, and the other rental information from the RentTable for each of the five movie DVD's



Does that help clarify, if you have other questions I will be happy to try and ans. Good Luck on the test tomorrow.

Answer 2

Hey I have a business A-Level exam on Wednesday, my ICT A-level exam was too easy :)



Alright so when tables r linked according to field what happens is that when a field in one table is changed, the same linked fields in other fields change as well, so this reduces errors and less data entry work to do.



When u produce reports u won't have to select multiple fields from different tables cause a field that is linked can be selected and this again reduces complexity in a report.



Simple as that :)



Take care and good luck for your exam.

Answer 3

Because if you have multiple categories or similar, you do not need to enter the categories in every table, you can link a category table to any other and use the ID of the category. The same rule would apply to customer orders, Either you need multiple entries of all the user data for each item they buy, or you have one entry and a link table to identify the items they bought.

Answer 4

Lets say one table has the name, address and phone of the renter, and the other has the DVDs that he rented and their status (is it still out, did he return it, did he pay).



You could have one table that has the name, address, phone, DVD and status for every rental.



Or you could have one table with the name, DVD, and status linked to another file table with the renters address and phone. That way you don't have to enter in the address and phone for every rental, you just link to it by name.