Enhancing crosstabs

When you have provided the data definitions, the crosstab
is functional, but you can enhance it before using it. Because a
crosstab is a grid DataWindow object, you can enhance a crosstab using
the same techniques you use in other DataWindow objects. For example, you
can:

• Sort or filter rows
• Change the column headers
• Specify fonts, colors, mouse pointers, and borders
• Specify column display formats

For more on these and the other standard enhancements
you can make to DataWindow objects, see Chapter 19, “Enhancing DataWindow Objects .”

The rest of this section covers topics either unique to crosstabs
or especially important when working with crosstabs:

• “Specifying basic properties”
• “Modifying the data
  associated with the crosstab”
• “Changing the names used
  for the columns and rows”
• “Defining summary statistics”
• “Cross-tabulating ranges
  of values”
• “Creating static crosstabs”
• “Using property conditional
  expressions”

Specifying basic properties

Crosstabs are implemented as grid DataWindow objects, so you can
specify the following grid properties for a crosstab:

• When grid lines are displayed
• How users can interact with the crosstab at
  runtime

To specify the crosstab’s basic properties:

1. In the Properties view, select the General
   tab.

2. Specify basic crosstab properties.

Table 27-2 lists
basic crosstab properties.

Table 27-2: Basic properties for crosstabs

Option	Result
Display	On — Grid lines always display. Off — Grid lines never display (columns cannot be resized at runtime). Display Only — Grid lines display only when the crosstab displays online. Print Only — Grid lines display only when the contents of the crosstab are printed.
Column Moving	Columns can be moved at runtime.
Mouse Selection	Data can be selected at runtime (and, for example, copied to the clipboard).
Row Resize	Rows can be resized at runtime.

Modifying the data associated with the crosstab

When you initially define the crosstab, you associate the
crosstab rows and columns with columns in a database table or other
data source. You can change the associated data anytime in the Crosstab
Definition dialog box.

To open the Crosstab Definition dialog box:

1. Position the mouse below the footer band
   in the workspace and display the pop-up menu.

2. Select Crosstab from the pop-up menu.

   The Crosstab Definition dialog box displays.

To modify the data associated with a crosstab:

1. In the Crosstab Definition dialog box,
   fill in the boxes for Columns, Rows, and Values as described in “Associating data with
   a crosstab “.

2. Click OK.

Changing the names used for the columns and rows

Sometimes names of columns in the database might not be meaningful.
You can change the names that are used to label rows and columns
in crosstabs so that the data is easier to understand.

To change the names used in crosstabs:

1. In the Crosstab Definition dialog box,
   double-click the name of the column in the Source Data box.

   The New Name dialog box displays:

2. Specify the name you want used to label the corresponding
   column. You can have multiple-word labels by using underscores:
   underscores are replaced by spaces in the Design view and at runtime.

3. Click OK.

   PowerBuilder changes the column name in the Source Data box
   and anywhere else the column is used.

Example

For example, if you want the product column
to be labeled Printer Model, double-click product in
the Crosstab Definition dialog box and specify printer_model in
the New Name dialog box.

When the crosstab runs, you see this:

Defining summary statistics

When you generate a crosstab, the columns and rows are automatically
totaled for you. You can include other statistical summaries in
crosstabs as well. To do that, you place computed fields in the
workspace.

To define a column summary:

1. Enlarge the summary band to make room for
   the summaries.

2. Select Insert>Control>Computed
   Field from the menu bar.

3. Click the cell in the summary band where you want
   the summary to display.

   The Modify Expression dialog box displays.

4. Define the computed field.

   For example, if you want the average value for a column, specify avg(units
   for all), where units is
   the column providing the values in the crosstab.

For example, this is a crosstab that has been enhanced to
show averages and maximum values for each column. This is the Design
view:

This is the crosstab at runtime:

To define a row summary:

1. Select Insert>Control>Computed
   Field from the menu bar.

2. Click the empty cell to the right of the last
   column in the detail band.

   The Modify Expression dialog box displays.

3. Define the computed field. You should use one
   of the crosstab functions, described next.

Using crosstab functions

There are nine special functions you can use only in crosstabs: CrosstabAvg, CrosstabAvgDec, CrosstabCount, CrosstabMax, CrosstabMaxDec, CrosstabMin, CrosstabMinDec, CrosstabSum,
and CrosstabSumDec.

These functions are listed in the Functions box when you define
a computed field in a crosstab:

Each of these functions returns the corresponding statistic
about a row in the crosstab (average, count, maximum value, minimum
value, or sum). You place computed fields using these functions
in the detail band in the Design view. Use the functions with the Dec suffix
when you want to return a decimal datatype.

By default, PowerBuilder places CrosstabSum and CrosstabSumDec in
the detail band, which returns the total for the corresponding row.

How to specify the functions

Each of these functions takes one numeric argument, which
refers to the expression defined for Values in the Crosstab Definition
dialog box. The first expression for Values is numbered 1, the second
is numbered 2, and so on.

Generally, crosstabs have only one expression for Values,
so the argument for the crosstab functions is 1. So, for example,
if you defined sum(units for crosstab) as
your Values expression, PowerBuilder places CrosstabSum(1) in
the detail band.

If you want to cross-tabulate both total unit sales and a
projection of future sales, assuming a 20 percent increase in sales
(that is, sales that are 1.2 times the actual sales), you define
two expressions for Values:

Here CrosstabSum(1) returns
the total of sum(units for crosstab) for the
corresponding row. CrosstabSum(2) returns
the total for sum(units * 1.2 for crosstab).

For more information

For complete information about defining computed
fields, see Chapter 19, “Enhancing DataWindow Objects .”

For more about the crosstab functions, see the DataWindow
Reference
.

Cross-tabulating ranges of values

You can build a crosstab where each row tabulates a range of
values, instead of one discrete value, and you can make each column
in the crosstab correspond to a range of values.

For example, in cross-tabulating departmental salary information,
you might want one row in the crosstab to count all employees making
between $30,000 and $40,000, the next row to count
all employees making between $40,000 and $50,000,
and so on.

To cross-tabulate ranges of values:

1. Determine the expression that results in
   the raw values being converted into one of a small set of fixed
   values.

   Each of those values will form a row or column in the crosstab.

2. Specify the expression in the Columns or Rows
   box in the Crosstab Definition dialog box.

   You choose the box depending on whether you want the columns
   or rows to correspond to the range of values.

3. In the Values column, apply the appropriate aggregate
   function to the expression.

Example

This is best illustrated with an example.

You want to know how many employees in each department earn
between $30,000 and $40,000, how many earn between $40,000
and $50,000, how many earn between $50,000 and $60,000,
and so on. To do this, you want a crosstab where each row corresponds
to a $10,000 range of salary.

The first step is to determine the expression that, given
a salary, returns the next smaller salary that is a multiple of $10,000.
For example, given a salary of $34,000, the expression
would return $30,000, and given a salary of $47,000, the
expression would return $40,000. You can use the Int function
to accomplish this, as follows:

That expression divides the salary by 10,000 and takes the
integer portion, then multiplies the result by 10,000. So for $34,000,
the expression returns $30,000, as follows:

With this information you can build the crosstab. The following
uses the Employee table in the EAS Demo DB:

1. Build a crosstab and retrieve
   the dept_id and salary columns.
2. In the Crosstab Definition dialog box, drag the dept_id column
   to the Columns box.
3. Drag the salary column to the
   Rows box and to the Values box and edit the expressions.
   In the Rows box, use:
   PowerBuilder

   int(salary/10000) * 10000

   1	int(salary/10000) * 10000

   In the Values box, use:

   PowerBuilder

   count(int(salary/10000) * 10000 for crosstab)

   1	count(int(salary/10000) * 10000 for crosstab)

   For more on providing expressions in a crosstab,
   see “Using expressions”.

4. Click OK.
   This is the result in the Design view:

   
   
   This is the crosstab at runtime:

   

You can see, for example, that 2 people in department 400
and 5 in department 500 earn between $20,000 and $30,000.

Displaying blank values as zero

In the preceding crosstab, several of the cells in the grid
are blank. There are no employees in some salary ranges, so the
value of those cells is null. To make the crosstab easier to read,
you can add a display format to fields that can have null values
so that they display a zero.

To display blank values in a crosstab as zero:

1. Select the column you want to modify and
   click the Format tab in the Properties view.

2. Replace [General] in the Format
   box with ###0;###0;0;0.

   The fourth section in the mask causes a null value to be represented
   as zero.

Creating static crosstabs

By default, crosstabs are dynamic: when you run them, PowerBuilder retrieves the
data and dynamically builds the columns and rows based on the retrieved data.
For example, if you define a crosstab that computes sales of printers
and a new printer type is entered in the database after you define
the crosstab, you want the new printer to be in the crosstab. That
is, you want PowerBuilder to build the rows and columns dynamically
based on current data, not the data that existed when the crosstab
was defined.

Occasionally, however, you might want a crosstab to be static.
That is, you want its columns to be established when you define
the crosstab. You do not want additional columns to display in the
crosstab at runtime; no matter what the data looks like, you do
not want the number of columns to change. You want only the updated
statistics for the predefined columns. The following procedure shows
how to do that.

To create a static crosstab:

1. In the wizard page or in the Crosstab Definition
   dialog box, clear the Rebuild Columns At Runtime check box.

2. Define the data for the crosstab as usual, and
   click OK.

What happens

With the check box cleared, instead of immediately building
the crosstab’s structure, PowerBuilder first retrieves the
data from the database. Using the retrieved data, PowerBuilder then
builds the crosstab structure and displays the workspace. It places
all the values for the column specified in the Columns box in the
workspace. These values become part of the crosstab’s definition.

For example, in the following screenshot, the four values
for Quarter (Q1, Q2, Q3, and Q4) are displayed in the Design view:

At runtime, no matter what values are in the database for
the column, the crosstab shows only the values that were specified
when the crosstab was defined. In the printer example, the crosstab
always has the four columns it had when it was first defined.

Making changes

You can modify the properties of any of the columns in a static
crosstab. You can modify the properties of each column individually,
since each column is displayed in the workspace as part of the crosstab’s
definition. For example, in the printer crosstab you can directly
modify the way values are presented in each individual quarter,
since each quarter is represented in the Design view. (The values
are shown as units, units_1, units_2,
and units_3.)

Using property conditional expressions

As with other DataWindow objects, you can specify property conditional expressions
to modify properties at runtime. You can use them with either dynamic
or static crosstabs. With dynamic crosstabs, you specify an expression once
for a column or value, and PowerBuilder assigns the appropriate properties
when it builds the individual columns at runtime. With static crosstabs,
you have to specify an expression for each individual column or value,
because the columns are already specified at definition time.

Example

In the following crosstab, an expression has been specified
for Units:

The expression is for the Font.Weight property of the units column:

The expression specifies to use bold font (weight = 700)
if the number of units is greater than 100. Otherwise, use normal
font (weight = 400).

This is the crosstab at runtime:

Values larger than 100 are shown in bold.

For more information about property conditional
expressions, see Chapter 24, “Highlighting Information
in DataWindow Objects.”

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