- Trigger on the table management functions
- Variables used to manage the triggers
- Previous versions
In french: HDécritTrigger
Not available with these kinds of connection
Adds or modifies a trigger on an HFSQL data file. A trigger is a WLanguage procedure automatically called by the HFSQL engine whenever an HFSQL function is run. UPDATE, INSERT or DELETE queries also execute the trigger (Caution: the trigger is executed on tables accessed via a Native Connector).
This function is only available on the client side. Use HDescribeServerTrigger
to define a server trigger for an HFSQL Client/Server database.
// In the initialization code of the project
TriggerResult is boolean
// Create a trigger for all the analysis files
TriggerResult = HDescribeTrigger("*", "HADD,HMODIFY," + ...
"HDELETE, HCROSS,HWRITE", "CheckUserRights", hTriggerBefore)
// "CheckUserRights" is a global procedure of the project
IF TriggerResult = False THEN
Error("Error on a trigger: " + HErrorInfo)
<Result> = HDescribeTrigger(<List of HFSQL data files> , <List of HFSQL functions> , <WLanguage procedure> , <Type of trigger>)
- True if the operation was performed,
- False if a problem occurs. HErrorInfo is used to identify the error.
<List of HFSQL data files>: Character string
Logical name of one or more HFSQL data files.
To specify several names of data files, the names of the data files must be separated by a comma (",").
To use all the data files found in the analysis, this parameter must be equal to "*".
<List of HFSQL functions>: Character string
Name of one or more HFSQL or TableXXX functions on which the trigger must be implemented. To specify several names of functions, the names of functions must be separated by a comma (","). You have the ability to define triggers on the following functions:
<WLanguage procedure>: Procedure name
Name of the WLanguage procedure that will be run when a trigger is activated on the specified HFSQL functions.
<Type of trigger>: Integer constant
Indicates the type of trigger.
|hTriggerAfter||The procedure is run after the HFSQL function.|
|hTriggerBefore||The procedure is run before the HFSQL function.|
Trigger on the table management functions
When using one of these functions for handling the tables, if a trigger is defined for the corresponding HFSQL function, the trigger is automatically activated.
Variables used to manage the triggers
A trigger procedure accepts no parameter. However, some HFSQL state variables are positioned before each call:
|H.Action||Character initialized to "A" for a Before trigger and to "P" for an After trigger.|
|H.FileName||Character string: Logical name of the data file whose trigger is activated|
|H.ToDo||During the execution of a before trigger:|
- cancel the execution of the HFSQL function by assigning "A" to the HFSQL state variable: H.ToDo = "A". In this case, the action is not performed and the function (HAdd, HModify, etc.) returns True (no error).
- cancel the execution of the current HFSQL function by assigning "E" to the HFSQL state variable: H.ToDo = "E". In this case, the action is not performed and the function (HAdd, HModify, etc.) returns False. The error message is as follows: "The action on XXX file was interrupted by the trigger".
|H.TriggerFunction||Character string: Name of the HFSQL function that activated the trigger|
: When a "BEFORE" trigger and an "AFTER" trigger are associated with an HFSQL function, if "BEFORE" cancels the execution of the HFSQL function (by setting H.ToDo to "A"), "AFTER" is not run.
This function replaces HDescribeTrigger_55, which is kept for compatibility with WINDEV 5.5.
This page is also available for…
Not only on HFCS databases
According to the online help: HdescribeTrigger "Adds or modifies a trigger on a HFSQL data file"
I have used HdesdcribeTrigger on Postgresql databases also.