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Intro To Data Modeling


Lesson 3

The relational database software comes to the rescue again by making data entry easy. The software knows that you're working on more than one file at a time and that the files have related information, for example, it knows that each patron name in the intersection file, will have a match in the patron file.

Therefore, the software sets up your data entry so that you only have to type in the information once and it automatically copies the info that you typed to the related files. But because the software knows what you're up to, it can do some other very helpful things.

For example, let's say you mistyped Andrew's name (maybe you typed "Andy" by mistake) while adding a record to the intersection file. The software would see that there's no "Andy" in the patron file and give you a warning. This greatly cuts down on errors.

Same thing if you were typing in a book a patron was checking out and you misspelled the book name. The software would tell you "That book doesn't exist in the book file!"

Remember that Andrew's (or any patron's) address only appears once, and that's in the patron file. So if Andrew moves, his address information only has to be updated one time in one place, and no matter how many books he checks out, his address will always be current.

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