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Tables of Data

The foundational idea underneath relational databases is a simple but powerful structure. Each table is a set of sets, and within a single table all of these sets have the same data structure, containing a list of named fields and their values. For convenience, each set within a table is called a row, and each field within that row is part of a larger named column, as shown in Figure B-1. It looks a lot like a spreadsheet with named columns and unnamed rows.

The classic row–column approach to tables
Figure B-1. The classic row–column approach to tables

The resemblance to a spreadsheet is only superficial, however. Spreadsheets are built on grids, but those grids can have anything in them that any user wants to put in any given place in the spreadsheet. It’s possible to build a spreadsheet that is structured like a database table, but it’s definitely not required. Databases offer much less of that kind of flexibility, and in return can offer tremendous power because of their obsession with neatly ordered data. Every row within a table has to have the same structure for its data, and calculations generally take place outside of the tables, not within them. Tables just contain data.


  

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