MIS 385/MBA 664 Systems Implementation with DBMS/ Database Management Dave Salisbury ( ) (web site)

Procedures, triggers & macros in Teradata Stored Procedures Program modules that execute on demand Written in SQL Control and condition handling statements More powerful than macros; more sophisticated procedural logic and error handling Triggers Routines that execute in response to a database event e.g. INSERT, UPDATE, or DELETE Macros Series of SQL statements Executable with a single command

Triggers in Teradata Triggers are procedures associated with a table Fire upon meeting of trigger condition Used in database to react to specific situations enforcing data integrity rules deriving specific values Two general types Row triggers Statement triggers Simple example of using a trigger might be the autonum datatype in Access (when calling a stored procedure to increment the value by 1)

One sample trigger This sample will store the following fields in a table (old_customer_t) on the occurrence of the event (deletion of a customer (NOTE: need to create the table first). Customer_ID Customer_Name Customer_City Customer_State

General syntax for triggers CREATE[REPLACE] ENABLED[DISABLED] BEFORE|AFTER INSERT|DELETE OF ON REFERENCING OLD [row|table] AS NEW [row|table] AS FOR EACH ROW|STATEMENT WHEN (search_condition SQL statement) ;

Code for delete_customer trigger CREATE TRIGGER delete_customer AFTER DELETE ON CUSTOMER_T REFERENCING OLD as O FOR EACH ROW INSERT INTO ARCHIVE_CUSTOMER_T (O.Customer_ID, O.Customer_Name, O.Customer_City, O.Customer_State);

Show date/time with SELECT & EXTRACT To see current SYSTEM DATE SELECT DATE; - gives output as “11/11/2008″ EXTRACT SELECT EXTRACT (MONTH FROM date); - “11” SELECT EXTRACT (YEAR FROM date); - “2008” SELECT EXTRACT (DAY FROM date); - “11” For HOUR MINUTE and SECONDS extractions, use TIME instead. SELECT TIME; - gives output as “18:25:01” SELECT EXTRACT (MINUTE FROM time); - “18” SELECT EXTRACT (HOUR FROM time); - “25” SELECT EXTRACT (SECOND FROM time); - “01” All of the above can be implemented using macros

The procedure from the book First alter the product_t table Then create the procedure Then call the procedure

Embedded and Dynamic SQL Embedded SQL Including hard-coded SQL statements in a program written in another language such as C or Java Dynamic SQL Ability for an application program to generate SQL code on the fly, as the application is running