Extended Functions of ASF › Selecting Data at Definition Time

Selecting Data at Definition Time

The Extended Selection Definition screen is used to define selection criteria for a table. The criteria specified are used to select the data to be included in the table. Selection definition is applied most often to views, but can be specified for stored tables. Defining selection criteria can serve the following purposes:

• When defined for a view, the criteria are used to select the source data to be included in the view.
• When defined for a stored table or view, the criteria are used to edit data added to the table.

Use Edit Table for Editing

The use of selection definition for editing data is limited, particularly through the application generated by ASF. When a row being added does not meet the selection criteria defined, the message INVALID DATA is displayed, with no indication as to which column entry is in error. Edit tables are more effective and should be used when appropriate. The primary purpose of selection definition is to select rows for inclusion in a view.

Defining Selection Criteria

Criteria for selection definition are specified in the same way as criteria for data selection at display time. Selection criteria are defined in the following two ways:

• Fixed-format expressions allow you to define selection criteria on a column-by-column basis, using simple logical expressions (including arithmetic expressions) that contain a single operand (such as EQ, GT, or MATCHES). With fixed-format expressions, you can define criteria for more than one column. The system then selects rows where all expressions are true (that is, using an implied AND as a conjunction between each fixed-format expression).
• Freeform expressions allow you to define selection criteria using compound logical expressions that contain several operands connected with AND, OR, and NOT. Freeform expressions can be used in addition to, or instead of, fixed-format expressions.
• Freeform and fixed-format expressions used together simply are treated as one expression with AND as the operator.

The Extended Selection Definition screen shown below illustrates the use of both fixed-format and freeform expressions to define selection criteria. For more information about rules on entering selection criteria, see the discussion on the Data Selection screen in the chapter "Basic Screens".

                                                    CA
  XSEL   CA - Automatic System Facility       *Extended Selection Definition*
  DC560603 ENTER SELECTION CRITERIA
  Table Name: EMPLOYEE1
               _ PF1 - Help      _ PF2 - Message Screen          Page:  1  of  1

   ID           Column Name                      Selection Criteria
  0001 EMP-ID-0415
  0002 EMP-FIRST-NAME-0415
  0003 EMP-LAST-NAME-0415
  0004 EMP-STREET-0415
  0005 EMP-CITY-0415
  0006 EMP-STATE-0415
  0007 EMP-ZIP-0415                     MATCHES '02###'     1
  0008 EMP-PHONE-0415                   MATCHES '617#######'
  0009 EMP-STATUS-0415                  '01'                
  0010 EMP-START-YEAR-0415              GE '1980'           




                          Additional Selection Criteria
 $7 OR $82

1. Fixed-format expression
2. Freeform expression