Contents
Which triggering events can cause a trigger to fire?
The events that fire a trigger include the following:
- DML statements that modify data in a table ( INSERT , UPDATE , or DELETE )
- DDL statements.
- System events such as startup, shutdown, and error messages.
- User events such as logon and logoff. Note: Oracle Forms can define, store, and run triggers of a different sort.
Can not have a trigger associated with it MySQL?
MySQL trigger limitations MySQL triggers cannot: Use SHOW , LOAD DATA , LOAD TABLE , BACKUP DATABASE, RESTORE , FLUSH and RETURN statements. Use statements that commit or rollback implicitly or explicitly such as COMMIT , ROLLBACK , START TRANSACTION , LOCK/UNLOCK TABLES , ALTER , CREATE , DROP , RENAME.
How can we specifies a row-level trigger?
Row-level trigger is identified by the FOR EACH ROW clause in the CREATE TRIGGER command. Statement-level triggers execute once for each transaction. For example, if a single transaction inserted 500 rows into the Customer table, then a statement-level trigger on that table would only be executed once.
How often is a row trigger fired in Oracle?
A row trigger is fired each time the table is affected by the triggering statement. For example, if an UPDATE statement updates multiple rows of a table, a row trigger is fired once for each row affected by the UPDATE statement. If a triggering statement affects no rows, a row trigger is not run.
Why do I get 1 Row affected message?
The “1 row affected” message is being generated in the outer scope (the scope in which the INSERT statement is being run) rather than within the scope of the trigger, and is being generated because the trigger is running to completion – so far as the outer statement is concerned, it’s been succesful.
Can you have multiple triggers for the same table?
You can have multiple triggers of the same type for the same statement for any given table. For example, you can have two BEFORE statement triggers for UPDATE statements on the employees table. Multiple triggers of the same type permit modular installation of applications that have triggers on the same tables.
Can a conditional predicate be used to fire a trigger?
When multiple types of SQL statements can fire a trigger, you can use conditional predicates to detect the type of triggering statement. In this way, you can create a single trigger that runs different code based on the type of statement that fires the trigger.