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Before trigger is for checking data and deciding if operation should be permitted. If exception is thrown from before trigger then operation is aborted and no data are changed. In DB2 before triggers are read only — you can't modify data in before triggers. After triggers are designed for post processing after requested change was performed.
Template: Check page on delete. 1 language. ... Download as PDF; Printable version ...
The template has been designed to be usable in a similar manner to creating a normal internal link, and takes two to three parameters depending upon how you wish to use it. To create the example link from before to this page's edit page using the querylink template, the following wikitext markup was used:
A trigger cannot be attached to more than one operation (INSERT, DELETE, UPDATE), so a trigger must be created for each operation. The old and new values are exposed as fields of a record data structures. The names of these records can be defined, in this example they are named as O for old values and N for new values.
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.
Before doing changes to a template it can be good to first copy the template code to a sandbox and run some testcases, since the template might be visible on thousands or even millions of pages. If you create subpages named exactly " /sandbox " and " /testcases " to a template then the green {{documentation}} box on the template auto-detects ...
DELETE requires a shared table lock; Triggers fire; DELETE can be used in the case of: database link; DELETE returns the number of records deleted; Transaction log - DELETE needs to read records, check constraints, update block, update indexes, and generate redo / undo. All of this takes time, hence it takes time much longer than with TRUNCATE
In computer programming, create, read, update, and delete (CRUD) are the four basic operations (actions) of persistent storage. [1] CRUD is also sometimes used to describe user interface conventions that facilitate viewing, searching, and changing information using computer-based forms and reports .