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Pre-Query trigger in Oracle D2k / Oracle Forms

2024-08-29 07:29:16   215人阅读

Pre-Query trigger in Oracle D2k / Oracle Forms

Description
Fires during Execute Query or Count Query processing, just before Form Builder constructs and issues
the SELECT statement to identify rows that match the query criteria.
Definition Level form or block
Legal Commands
SELECT statements, unrestricted built-ins
Enter Query Mode no

See also: Define Custom Filter Using Pre-Query Trigger

Usage Notes
Use a Pre-Query trigger to modify the example record that determines which rows will be identified by
the query.
On Failure
The query is canceled. If the operator or the application had placed the form in Enter Query mode, the
form remains in Enter Query mode.
Fires In
COUNT_QUERY
EXECUTE_QUERY
Open the Query
Prepare the Query
See Process Flowcharts
Pre-Query trigger examples
Example
This example validates or modifies query criteria for a database block query.
BEGIN
/*
** Set the ORDER BY clause for the current block
** being queried, based on a radio group
** called ’Sort_Column’ in a control block named
** ’Switches’. The Radio Group has three buttons
** with character values giving the names of
** three different columns in the table this
** block is based on:
**
** SAL
** MGR,ENAME
** ENAME
*/
Set_Block_Property(’EMP’,ORDER_BY, :Switches.Sort_Column);
/*
** Make sure the user has given one of the two
** Columns which we have indexed in their search
** criteria, otherwise fail the query with a helpful
** message
*/
IF :Employee.Ename IS NULL AND :Employee.Mgr IS NULL THEN
Message(’Supply Employee Name and/or Manager Id ’||
’for Query.’);
RAISE Form_trigger_Failure;
END IF;
/*
** Change the default where clause to either show "Current
** Employees Only" or "Terminated Employees" based on the
** setting of a check box named ’Show_Term’ in a control
** block named ’Switches’.
*/
IF Check box_Checked(’Switches.Show_Term’) THEN
Set_Block_Property(’EMP’,DEFAULT_WHERE,’TERM_DATE IS NOT
NULL’);
ELSE
Set_Block_Property(’EMP’,DEFAULT_WHERE,’TERM_DATE IS NULL’);
END IF;
END;

Pre-Query trigger in Oracle D2k / Oracle Forms


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