The Automatic System Facility › Data Tables

Data Tables

Data tables are two-dimensional tables that consist of columns and rows. A column:

• Has entries containing a single type of data
• Is displayed vertically
• Is identified by name

A row:

• Contains one value in each column
• Is displayed horizontally
• Is not named

       Column
      ┌-------┐
      │ NUMBER│  FIRST NAME  LAST NAME     ADDRESS          CITY        STATE
      │       │
      │ 2453  │  CATHERINE   HALBURN       57 MAIN ST       BOSTON      MA
      │ 1134  │  JON         BURKE         23 SOUTH ST      NEWTON      MA
      │ 1469  │  SUSAN       MAYO          60 COMMONS ST    BOSTON      MA
      │ 0921  │  LINDA       IOSSA         82 THOMAS AVE    WESTWOOD    MA
      │ 0286  │  ANGELA      CAMPANIELLO   27 SHELBY ST     WORCESTER   MA
     ┌┼-------┼------------------------------------------------------------┐
  Row││ 1373  │  MARGARET    BARBER        86 JONES AVE     DEDHAM      MA │
     └┼-------┼------------------------------------------------------------┘
      └-------┘
  

Two Kinds of Data Tables

Data tables can be either stored tables or views:

• Stored tables are physically stored in the database and are independent of any other tables.
• Views are derived from other tables and records; they do not contain data themselves, but contain a definition of data from the source tables. When a view is accessed, data is retrieved from the source tables in which it is stored.

Stored tables and views are illustrated in the figure below.