HP 3000 Manuals

HP ALLBASE/BRW Reference Manual

Formulas 

Formulas include:

   *   table calculated items

   *   layout calculated items

   *   table functions

   *   layout functions

Calculated Items 

Calculated items are items that are created from a formula that you
define.  Once created, calculated items can be used in a report just like
an item projected from a final access table, or an HP ALLBASE/BRW
standard item.  Calculated items are split into two categories, table
calculated items and layout calculated items, depending upon whether they
are to be created when the tables are built or when the report is
formatted.

Table Calculated Items 

Table calculated items are defined within a table .  They are created
when the table is constructed.  The Table Calc Item screen and the Table
Calc Item Formula screen are used to define the item and its formula.

Characteristics 

Table calculated items have these characteristics: 

   *   Outside the table in which they have been defined, they can be
       used like any other item projected from the table.  (See Chapter 6
        for details about projecting items).  For example, they can
       be:
              printed
              written to an output file
              used for selection
              used for sorting
              used in another calculation formula

   *   They can be any one of the HP ALLBASE/BRW item types:
              N - fixed-point numeric
              R - floating-point real
              I - integer
              S - string
              D - date
              T - time

   *   They can be calculated from source table items, from other
       calculated items or functions defined in the same table, or from
       parameters or constants.

Restrictions 

Restrictions on table calculated items are:

   *   They cannot be used on the Define Relation screen for the same
       table in which they are defined.

   *   They cannot use column calculation results (or certain standard
       items, such as PAGE) as arguments.  See "Standard Items" later in
       this chapter for a list of available standard items.

Example 

Here is an example of a table calculated item, BALANCE-DUE:


            

This is the Table Calc Item screen for BALANCE-DUE. It is a numeric item.


            

You define the formula for a table calculated item on the Table Calc Item
Formula screen.  This formula can use any of the arguments and operators
allowed in the Calculation Language, and must obey its syntax rules.
These are described in the "Arguments and Syntax" section of this
chapter.

When the table is constructed, every row of the table will have an item
called BALANCE-DUE that you can use in the report.  This item will behave
exactly like any other Numeric item that you project from the table.
Each value of BALANCE-DUE will be equal to the value of AMOUNT, minus the
value of PAID-AMOUNT, on that row of the table.

Layout Calculated Items 

Layout calculated items are very similar to table calculated items, but
they are defined within the report layout.  Layout calculated items are
calculated when the report is formatted.  The Layout Calc Item screen and
the Layout Calc Item Formula screen are used to define the item and its
formula.

Characteristics 

The characteristics of layout calculated items are exactly the same as 
for table calculated items, except that:   

   *   Layout calculated items cannot be used in formulas for table
       calculated items, relation conditions, or table functions.

   *   Layout calculated items can use column calculation results in
       their calculations; for example, a column total or an average
       value can be used in the calculation for a layout calculated item.

   *   Layout calculated items can be calculated for each detail lineset,
       or, you can specify that they be calculated only for certain
       linesets.

Restrictions 

Restrictions on layout calculated items are:

   *   They cannot be used for selection or sorting.


NOTE  For better performance: 

         *   Table calculated items are calculated as early as possible
             in the data access for a report.  This means that they are
             only calculated when their arguments change.

             Table calculated items generally can improve performance if
             they replace the items from which they are calculated, so
             reducing the width of the table.

         *   Layout calculated items are calculated, by default, once for
             each detail.  They can improve performance if they do not 
             replace (that is, are additional to) the items from which
             they are calculated, since layout calculated items are not
             part of any table.

         *   If you use a layout calculated item only on a specific
             break, you can further improve performance if you specify
             that it is to be calculated only if that break occurs.

         *   Calculated Item performance is further discussed in Chapter
             19 , "Performance Considerations."


Examples 

Suppose you are defining BALANCE-DUE as a table calculated item.  Doing
that would be efficient if you did not want items AMOUNT and PAID-AMOUNT
in your report.  That is, you would calculate and project BALANCE-DUE,
and not project AMOUNT and PAID-AMOUNT. This would save writing AMOUNT
and PAID-AMOUNT on every row of the table, when you did not in fact need
them.  For more information, see the "Compile Listing" section in Chapter
19 .

On the other hand, if you wanted items PAID-AMOUNT and AMOUNT in your
report, as well as BALANCE-DUE, you should define BALANCE-DUE as a layout
calculated item.  It would be calculated once for each detail line, but
would not add to the space on each row of the table.

Suppose, however, that you wanted the BALANCE-DUE only for the break on
CUSTOMER-NO. You would add item BALANCE DUE on the Define Lines screen
for that lineset, and specify CALC in the ColCalc field for BALANCE-DUE.
Then the item would only be calculated on that lineset.

MPE/iX 5.0 Documentation