Rules and procedures work together to provide a method of enforcing
the relationships in a database design without application programming.
You create procedures, which are stored in the DBEnvironment; then
you create rules that invoke the procedures when certain conditions
are met. This section shows how to create simple rules and
procedures. For more detailed information, refer to the chapter
"Constraints, Procedures and Rules" in the ALLBASE/SQL Reference Manual.
Creating a Procedure |
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You can create procedures that perform most database operations
when fired by a rule or when invoked in ISQL or in an
application program. The following example shows how to create
procedure PurchDB.RemovePart, which is invoked by the rule
described in the following section:
CREATE PROCEDURE PurchDB.RemovePart (PartNum CHAR(16) NOT NULL)
AS BEGIN
DELETE FROM PurchDB.Inventory WHERE PartNumber = :PartNum;
DELETE FROM PurchDB.SupplyPrice WHERE PartNumber = :PartNum;
END;
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For more detailed information, refer to the
"Using Procedures" section of the "Constraints, Procedures, and Rules" chapter in the ALLBASE/SQL Reference Manual and to the
"Using Procedures in Application Programs" chapter in the ALLBASE/SQL Advanced Application Programming Guide.
Creating a Rule |
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You can define rules that operate on specific tables in a database
whenever a particular type of data manipulation is performed.
The following example shows how to create a rule tied to
an update of the PurchDB.Parts table:
CREATE RULE PurchDB.RemovePart
AFTER DELETE FROM PurchDB.Parts
WHERE SUBSTRING(PartNumber,1,4) < > 'XXXX'
EXECUTE PROCEDURE PurchDB.RemovePart (OLD.PartNumber);
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The table on which the rule is defined is PurchDB.Parts.
The statement type required to trigger the procedure is the DELETE
operation. The condition that must be satisfied in addition to the
statement type of DELETE is that the first four characters in
PartNumber must not be "XXXX."
The procedure to be executed is PurchDB.RemovePart.
