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In the examples below each trigger is modifying a different table, by looking at what is being modified you can see some common applications of when different trigger types are used. The following is an Oracle syntax example of a row level trigger that is called AFTER an update FOR EACH ROW affected.
The trigger is said to be created on or defined on the item—which is either a table, a view, a schema, or the database. You also specify the timing point, which determines whether the trigger fires before or after the triggering statement runs and whether it fires for each row that the triggering statement affects.
The function GetDate() is used to get the system date and time, a specific RDBMS could either use another function name, or get this information by another way. Several RDBMS (Db2, MySQL) do not support that the same trigger can be attached to more than one operation (INSERT, DELETE, UPDATE).
For example, in Microsoft SQL Server, the key is retrieved via the SCOPE_IDENTITY() special function, while in SQLite the function is named last_insert_rowid(). Using a database-specific SELECT statement on a temporary table containing last inserted row(s).
Check constraints are parsed but ignored by all storage engines before MySQL version 8.0.15. [105] [106] Up until MySQL 5.7, triggers are limited to one per action / timing, meaning that at most one trigger can be defined to be executed after an INSERT operation, and one before INSERT on the same table. [107] No triggers can be defined on views ...
In this approach, triggers log events that happen to the transactional table into another queue table that can later be "played back". For example, imagine an Accounts table, when transactions are taken against this table, triggers would fire that would then store a history of the event or even the deltas into a separate queue table.
In the second example, REVOKE removes User1's privileges to use the INSERT command on the table Employees. DENY is a specific command. We can conclude that every user has a list of privilege which is denied or granted so command DENY is there to explicitly ban you some privileges on the database objects.:
Oracle Forms 3 was the first version to allow PL/SQL to be used within Forms triggers and procedures/SQL Functions could also be used as an undocumented feature. Forms 3 was a character mode application and was primarily used in terminals such as Digital VT220 and PCs running Microsoft DOS.