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Before Insert; 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.
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.
Change data capture both increases in complexity and reduces in value if the source system saves metadata changes when the data itself is not modified. For example, some Data models track the user who last looked at but did not change the data in the same structure as the data. This results in noise in the Change Data Capture.
Web2py is an open-source web application framework written in the Python programming language.Web2py allows web developers to program dynamic web content using Python.Web2py is designed to help reduce tedious web development tasks, such as developing web forms from scratch, although a web developer may build a form from scratch if required.
For example, LAST_INSERT_ID() for MySQL. Using a unique combination of elements from the original SQL INSERT in a subsequent SELECT statement. Using a GUID in the SQL INSERT statement and retrieving it in a SELECT statement. Using the OUTPUT clause in the SQL INSERT statement for MS-SQL Server 2005 and MS-SQL Server 2008.
The actual logic is contained in event-handler routines. These routines handle the events to which the main program will respond. For example, a single left-button mouse-click on a command button in a GUI program may trigger a routine that will open another window, save data to a database or exit the application.
This can happen in multi-threaded environments, or even in single-threaded environments when other code (typically called in the destruction of some object) resets the global variable before the checking code. The following example shows a way to avoid this problem (see or ; cf. ). But at the cost of not being able to use return values:
For example, if you need to load data into two databases, you can run the loads in parallel (instead of loading into the first – and then replicating into the second). Sometimes processing must take place sequentially. For example, dimensional (reference) data are needed before one can get and validate the rows for main "fact" tables.