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The four main types of triggers are: Row-level trigger: This gets executed before or after any column value of a row changes. Column-level trigger: This gets executed before or after the specified column changes. For each row type: This trigger gets executed once for each row of the result set affected by an insert/update/delete.
For optimistic locking each row has an independent version number, typically a sequential counter. This allows a process to atomically update a row and increment its counter only if another process has not incremented the counter. But CDC cannot use row-level versions to find all changes unless it knows the original "starting" version of every row.
In 1998, ASE 11.9.2 was rolled out with support for data pages locking, data rows (row-level locking), distributed joins and improved SMP performance. Indexes could now be created in descending order on a column, readpast concurrency option and repeatable read transaction isolation were added.
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. If the trigger is created on a table or view, then the triggering event is composed of DML statements, and the trigger is called a DML trigger.
"Trigger DXL" is defined in a "Trigger" and stored either in a Module, a Project, or in the Database root. There is no native interface for Triggers; a file-based DXL is needed to create or delete the Trigger. When the Trigger's specified Event occurs (such as Opening a Module) any Triggers associated with that event run in order of priority.
In relational databases, the log trigger or history trigger is a mechanism for automatic recording of information about changes inserting or/and updating or/and deleting rows in a database table. It is a particular technique for change data capturing , and in data warehousing for dealing with slowly changing dimensions .
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The Start date/time of the second row is equal to the End date/time (or next) of the previous row. The null End_Date in row two indicates the current tuple version. A standardized surrogate high date (e.g. 9999-12-31) may instead be used as an end date so that null-value substitution is not required when querying.