COMPUTER SCIENCE - DATA BASES - CHAPTER 14 / 2.3 (DATABASE STRUCTURES…
COMPUTER SCIENCE - DATA BASES - CHAPTER 14 / 2.3
Data validation is the process of automatically checking whether data entered is possible, realistic and sensible. Incorrect data can still be entered.
Data held within a database is only of use if it is reliable. Unreliable data can lead to serious consequences for users.
Criteria - a principle or standard by which something may be judged or decided. For example, only looking at data more than 3 in a certain field.
A common method of searching a database is using a query by example, which is a method of searching a database by stating the criteria to be searched. This needs to include: the table, the field, the criteria, any sorting that we want to apply, if we require the field to appear in the results or not.
SQL is a programming language that is used to maintain databases and to create queries.
Query - a method of searching a database for specific data.
Advantages - data only needs to be entered once, but it can be used repeatedly within the database; entering data only once reduces the chance of data errors; if a data entry error has occurred the data only has to be corrected once
Foreign key - a primary key that appears in another table in a relational database.
A database that has several tables linked by primary key fields. More complex in structure.
Index - a list of values or items.
Tables need a primary key, which is a field that holds data that uniquely identifies a record. The primary key is usually the first field, is the field that contains the index for each record, can be a number.
Data type is the format of the data in a field. each database field must be given a data type.
Field - one piece of data about an item in a database (column).
Record - a collection of data about one single item in a database (row).
Flat file database - a database whose records are stored in a single table.
Table - a structure in which data is stored in a database.
Data is stored in tables consisting of records and fields.
All databases have a structure that allows the data held within them to be stored in a logical and orderly manner.
Advantages - data can be easily sorted in a specific way, for example alphabetically; quick to find data; data can be filtered to retrieve only required data; allows easy sharing of data, for example over the internet or storage devices; validations can make sure data is possible, realistic and sensible; backups can be easily made; and saves space compared to paper-based
Can be used for: medical records, website history, TV channel list and library book information.
Data - raw facts and figures.
A database is a collection of data stored in a logical and order manner. Databases can be either paper-based or electronic.