Data Base columns
Database columns represent a column that is selected by the query and contains the data values for a report. For each column that you select in your query, Reports Builder automatically creates a column in the data model of your report.
Formula columns to create computed columns. It can be written using PL/SQL syntax. Formula columns names are generally preceded by “CF_” to distinguish them from data columns. A formula column performs a user-defined computation on the data of one or more column(s), including placeholder columns.
For example, : ITEMTOT *.07 is a formula that performs a computation on one column, while :SAL + :COMM performs a computation using two columns in a record. You create formulas in PL/SQL using the PL/SQL Editor.
Note: Formula columns should not be used to set values for parameters.
Creating or editing a formula column
To create or edit a formula column:
1. In the Data Model view, single-click the Formula Column in the tool palette, then:
· To create a column within a group, click in the group at the position you want the column placed in the hierarchy.
· To create a report-level column, click in an open area of the canvas region.
2. Double-click the formula column object to display the Property Inspector.
3. Under the Placeholder/Formula node, double click the PL/SQL Formula property field.
In the PL/SQL Editor, define the PL/SQL for the formula for example SAL * 0.07. 
Summary Columns
Summary columns perform a computation on another column’s data. These are used for calculating summary information like SUM,AVERAGE,COUNT,MINIMUM,MAXIMUM,%TOTAL. This column uses a set or predefined Oracle aggregate functions that can be applied to data or formula columns. Summary columns names are generally preceded by “CS_” to distinguish them from data columns.
Creating a summary column:
To create a summary column (for totals or subtotals) using the Data Wizard:
Ø In the Data Model view, click the query that contains the column you want to total.
Ø Choose Tools―> Data Wizard.
Ø On the Totals page, follow the wizard to add the desired summary to your report.
Note: For group reports, the Report Wizard and Data Wizard create n summary fields in the data model for each summary column you define: one at each group level above the column being summarized, and one at the report level. For example, if a report is grouped by division, and further grouped by department, then a summary column defined for a salary total would create fields for the sum of salaries for each division and each department group (group-level summaries), and the sum of all salaries (report-level summary).
To create a summary column (for totals or subtotals) using the tool palette:
Ø In the Data Model view, single-click in the tool palette, then:
o To create a column within a group, click in the group at the position you want the column placed in the hierarchy.
o To create a report-level column, click in an open area of the canvas region.
Ø Double-click the summary column object to display the Property Inspector.
Ø Under the Summary node:
o Set the Function property by choosing the type of summary you want from the list.
o Set the Source property to the column you want to summarize.
o Set the Reset At property to the group at which the summary column value resets.
Place Holders
A placeholder is a column for which we set the data type and value in PL/SQL that we define. Placeholder columns are useful when you want to selectively set the value of a column (E.g.: each time the nth record is fetched, or each time a record containing a specific value is fetched, and so on). We can set the value of a placeholder column in the following places:
§ the Before Report Trigger, if the placeholder is a report-level column
§ a report-level formula column, if the placeholder is a report-level column
§ a formula in the placeholder's group or a group below it (the value is set once for each record of the group)
To create or edit a placeholder column:
1. In the Data Model view, single-click the Placeholder Column tool in the tool palette.
· To create a column within a group, click in the group at the position you want the column placed in the hierarchy.
· To create a report-level column, click in an open area of the canvas region.
2. Double-click the placeholder column object.
3. In the Property Inspector, set the desired properties for the placeholder column.
4. Set the value of a placeholder column in:
· the Before Report trigger, if the placeholder is a report-level column
· a report-level formula column, if the placeholder is a report-level column
· a formula in the placeholder's group or a group below it (the value is set once for each record of the group)
