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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 ...
In SQL, the data manipulation language comprises the SQL-data change statements, [3] which modify stored data but not the schema or database objects. Manipulation of persistent database objects, e.g., tables or stored procedures, via the SQL schema statements, [3] rather than the data stored within them, is considered to be part of a separate data definition language (DDL).
It does not mean that both rows are common to that point in time, since -by definition- the value of EndDate is not included. There are two variants of the Log trigger, depending how the old values (DELETE, UPDATE) and new values (INSERT, UPDATE) are exposed to the trigger (it is RDBMS dependent):
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
Microsoft Excel is a spreadsheet editor developed by Microsoft for Windows, macOS, Android, iOS and iPadOS.It features calculation or computation capabilities, graphing tools, pivot tables, and a macro programming language called Visual Basic for Applications (VBA).
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.
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. If the trigger is created on a schema or the database, then the triggering event is composed of either DDL or database operation statements, and the trigger is called a system trigger. An INSTEAD OF ...
Functions could be used in SELECT statements, provided they do no data manipulation. However, procedures cannot be included in SELECT statements. A stored procedure can return multiple values using the OUT parameter, or return no value. A stored procedure saves the query compiling time. A stored procedure is a database object.