Selecting columns – PB Docs 150

To reorder the selected columns:

1. Drag a column in the Selection List with
   the mouse. Release the mouse button when the column is in the proper
   position in the list.

To select all columns from a table:

1. Move the pointer to the table name and
   select Select All from the pop-up menu.

To include computed columns:

1. Click the Compute tab to make the Compute
   view available (or select View>Compute if the Compute view
   is not currently displayed).

   Each row in the Compute view is a place for entering an expression
   that defines a computed column.

2. Enter one of the following:

   • An
     expression for the computed column. For example: salary/12

   • A function supported by your DBMS. For example,
     the following is a SQL Anywhere function:

     PowerBuilder

     substr("employee"."emp_fname",1,2)

     1	substr("employee"."emp_fname",1,2)

   You can display the pop-up menu for any row in the Compute
   view. Using the pop-up menu, you can select and paste the following
   into the expression:

   • Names
     of columns in the tables used in the DataWindow or pipeline

   • Any retrieval arguments you have specified

   • Functions supported by the DBMS

     About these functions

     The functions listed here are provided by your DBMS.
     They are not PowerBuilder functions. This is so because you are now
     defining a SELECT statement that will be sent
     to your DBMS for processing.

3. Press the Tab key to get to the next row to define
   another computed column, or click another tab to make additional
   specifications.

   PowerBuilder adds the computed columns to the list of columns
   you have selected.

About computed columns and computed fields

Computed columns you define in the SQL Select painter are added to
the SQL statement and used by
the DBMS to retrieve the data. The expression you define here follows
your DBMS’s rules.

You can also choose to define computed fields, which are created
and processed dynamically by PowerBuilder after the data has been
retrieved from the DBMS. There are advantages to doing this. For
example, work is offloaded from the database server, and the computed
fields update dynamically as data changes in the DataWindow object. (If
you have many rows, however, this updating can result in slower
performance.) For more information, see Chapter 19, “Enhancing DataWindow Objects .”