21.12. Summary

This chapter has covered a lot of ground to give you an overview of the basics of using a database in Python. It is more complicated to write the code to use a database to store data than Python dictionaries or flat files so there is little reason to use a database unless your application truly needs the capabilities of a database. The situations where a database can be quite useful are: (1) when your application needs to make many small random updates within a large data set, (2) when your data is so large it cannot fit in a dictionary and you need to look up information repeatedly, or (3) when you have a long-running process that you want to be able to stop and restart and retain the data from one run to the next.

Q-1: Which of the following is a situation where a database is useful?

• When your application needs to make many small random updates in a large data set.
• It is useful to use a database for very large sets of data, especially if you are making many updates.
• When your data fits in a dictionary.
• It is useful to use a database for very large sets of data, especially if you are accessing it frequently.
• When you only use the data once.
• A database is unnecessary if you are only processing it once.
• When you have a long-running process that you want to be able to stop and restart and retain the data from one run to the next.
• It is useful to use a database if you want to retain the run data.

You can build a simple database with a single table to suit many application needs, but most problems will require several tables and links/relationships between rows in different tables. When you start making links between tables, it is important to do some thoughtful design and follow the rules of database normalization to make the best use of the database’s capabilities. Since the primary motivation for using a database is that you have a large amount of data to deal with, it is important to model your data efficiently so your programs run as fast as possible.

Q-2: True or False? Databases need to have multiple tables to run quickly and efficiently.

• True
• Try again!
• False
• Databases can have a single table, but when they use multiple tables, they run fastest when the data is modeled efficiently.

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