Chapter 3 Building Conceptual Data Models

Specifying a domain's data type, length, and precision

Length and precision

The properties length and precision do not apply to all data types. Depending on data type, length may indicate a maximum or a fixed number of characters.

In the list of available data types, a variable indicates where you have to type a length or precision, as follows:

Variable Replace with
%n Length
%s Length with precision
%p Decimal precision

For example, if you are using Sybase Adaptive Server Anywhere and you choose the data type 

char(%n)
, you can choose a length of ten by typing 
char(10)
.

Undefined data type

All target DBMS allow you to select the <undefined> data type. The <undefined> data type indicates which domains remain without data types. If an <undefined> data type is present when you generate your database, it is replaced by the default data type for your database.

Steps To specify a data type for a domain from the list of domains:

  1. Select Model→Domains to open the List of Domains.
  2. Click the domain that you want to define.
  3. Select a data type from the list in the Data Type column and, if necessary, enter a length and precision.
  4. Click OK.

Steps To select a data type for a domain from its property sheet:

  1. Select Model→Domains to display the List of Domains.
  2. Click the domain that you want to define and then click the Properties tool to open its property sheet.
  3. Select a data type from the Data Type list or click the question mark button to the right of this list to open the list of standard data types.
  4. If necessary, enter values in the Length and Precision boxes.
  5. Click OK.

 

Copyright (C) 2007. Sybase Inc. All rights reserved.