ER/Studio - Embarcadero Technologies Product Documentation

USING ER/STUDIO > DEVELOPING THE PHYSICAL MODEL
• Set Null: The trigger verifies the existence of the foreign key values in the parent table's primary key. If the values
cannot be validated, then the trigger sets the foreign key value to null in the child table and then updates or
deletes the parent. For example, you have a parent table persons and a child table tasks, which through a
mandatory relationship share an id. By using a Set Null trigger you can allow the user to insert data into the
tasks table that contains an id for which their is no corresponding value in the persons table. The database will
not throw a referential integrity error in this case.
• Set Default: Sets the foreign key to its DEFAULT value, then updates or deletes the parent.
• Restrict: The trigger verifies the existence of foreign key values in the parent table's primary key. If the values
cannot be validated, then the trigger prevents the insertion, update or deletion of data. For example, you have a
parent table persons and a child table tasks, which through a mandatory relationship share an id. By using a
Restrict trigger you can prevent the user from inserting data into the tasks table that contains an id for which
their is no corresponding value in the persons table. The database will throw a referential integrity error in this
case.
• Cascade: If a primary key is updated or deleted, the trigger cascades that modification to corresponding foreign
key values in dependent tables.
Create a Scripted User-Defined Trigger
1 On the Data Model Window or the Data Model Explorer, select the table on which you want to create a Trigger.
2 Select Edit > Edit Database Table.
TIP: Alternatively, on the Data Model Window, open the Table Editor by double-clicking the table or
right-clicking the object and then selecting Edit Table.
3 On the Table Editor, click the Dependencies tab.
4 Click the Add button and then select Triggers > Scripted.
5 Complete the Trigger Editor and then click Finish to create the trigger.
The following describe options that require additional explanation:
• In order for code to be generated for procedural logic such as triggers and procedures, the results of the
trigger must be stored in a variable called resultstring. For example, in the Northwind.dm1 sample model,
the Data Dictionary lists a reusable trigger, SYSUPDATE, for the the Oracle platform. The code for this trigger
includes the following statement, which is required for code to be generated for the trigger:
resultstring = trigBody
• The Trigger Editor includes find and replace functionality for working with SQL text strings.
• Name: Lets you enter a trigger name or edit the existing one.
SQL tab
Lets you enter a CREATE TRIGGER statement for the trigger, or edit the existing script. If you do not want to
enter an SQL script, you can use the Import button to import it.
• Export: Lets you export the SQL script to a *.sql file. This is useful for when you want to create additional triggers
based on the one you are currently creating. You can export the code, and later import it into another procedure.
When you click Export, the Save As dialog box opens. Enter the file name. ER/Studio saves the files in the Model
folder, if you want to save your files in a different folder, browse and locate it.
• Import: Lets you import *.sql files. When you click Import, the Open dialog box opens. You can enter the name
of the *.sql file, or browse and locate it.
• Validate: Lets you validate the SQL script. If ER/Studio detects any errors, it returns them in a message box.
Errors include the error type, line, and column information.
EMBARCADERO TECHNOLOGIES > ER/STUDIO® 8.0.3 USER GUIDE 190