Tables, Columns, and Rows

First, a little terminology: If you’re already familiar with databases, you’ve heard alternative terms for the same concepts. Table 2.1 shows how interchangeable terms are related. Formal relational-model terms are in the first column, ANSI SQL standard and DBMS documentation terms are in the second column, and the third-column terms are holdovers from traditional (nonrelational) file processing. I use SQL terms in this book (even when I’m discussing the model).

Tables

From a user’s point of view, a database appears to be a collection of one or more tables (and nothing but tables). A table:

  • Is the database structure that holds data.

  • Contains data about a specific entity type. An entity type is a class of distinguishable ...

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