In a relational database, all data is held in tables, which are made up of rows and columns.
Each table has one or more columns, and each column is assigned a specific data type, such as an integer, a sequence of characters (for text), or a date. Each row in the table has a single value for each column.
For example, a table containing employee information can look like the following:
The tables in a relational database have some important characteristics:
The following table lists some of the formal and informal relational database terms describing tables and their contents, together with their equivalent in non-relational databases such as dBase and FoxPro. This document uses the informal terms.
|Informal relational term||Formal relational term||Non-relational term|
Each table in the database should hold information about a specific kind of thing, such as employees, products, or customers.
By designing a database this way, you can set up a structure that eliminates redundancy and the possible inconsistencies caused by redundancy. For example, both the sales and accounts payable departments might enter and look up information about customers. In a relational database, the information about customers is stored only once, in a table that both departments can access.
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