Additional DDS field definition functions

 

You can describe additional information about the fields in the physical and logical file record formats with function keywords (positions 45 through 80 on the DDS form). Some of the things you can specify include:

• Validity checking keywords to verify that the field data meets your standards. For example, you can describe a field to have a valid range of 500 to 900. (This checking is done only when data is typed on a keyboard to the display.)

• Editing keywords to control how a field should be displayed or printed. For example, you can use the EDTCDE(Y) keyword to specify that a date field is to appear as MM/DD/YY. The EDTCDE and EDTWRD keywords can be used to control editing. (This editing is done only when used in a display or printer file.)

• Documentation, heading, and name control keywords to control the description and name of a field. For example, you can use the TEXT keyword to document a description of each field. This text description is included in your compiler list to better document the files used in your program. The TEXT and COLHDG keywords control text and column-heading definitions. The ALIAS keyword can be used to provide a more descriptive name for a field. The alias, or alternative name, is used in a program (if the high-level language supports alias names).

• Content and default value keywords to control the null content and default data for a field. The ALWNULL keyword specifies whether a null value is allowed in the field. If ALWNULL is used, the default value of the field is null. If ALWNULL is not present at the field level, the null value is not allowed, character and hexadecimal fields default to blanks, and numeric fields default to zeros, unless the DFT (default) keyword is used to specify a different value.

 

Parent topic:

Describing database files using DDS