Database Concept
by Pepe Grof
1. A database is a persistent and organised store of related data.
2. Serial Files: A file of items one after another. This may be easy to manage with only a few pieces of data, but is inefficient to find things when you have lots.
3. Sequential Files: A serial file in order. Much faster than a serial file as you don't have to look one after another for a file.
4. Data Integrity: The state of data being as it should be, reflecting reality.
4.1. Validation: The process of checking data as it is to ensure that it is reasonable.
4.2. Verification: The process of checking data is true or correct.
5. Flat-File Database: A database consisting of only one table. Only needs to store a few things, so usually quite small. Made up of Fields and Records.
5.1. Fields: A characteristic of something stored in a database.
5.2. Record: All the data about one item in a database.
5.3. Entities: Something that we store data about in a database. It can be anything from the real world, such as a car or a bank account.
5.4. Attribute: A characteristic of an entity. In a data table, it becomes a field.
6. Data Redundancy: The unnecessary repetition of data. For instance, if someone orders 3 things from a company and all three are recorded, all the information might be the same except for the order item. On top of that, if the person changes address, all the others have to be updated, which is inefficient, eventually leading to complex processing problems.
