MySQL 触发器(Triggers) 在MySQL中,触发器(trigger)是一段绑定于table上的sql程序(stored program),这段程序在对表(db table)进行数据操作(insert, update, delete)时候触发并自动执行。 标准SQL定义了两种trigger类型: row level trigger statement level trigger MySQL仅支持 row level trigger。 创建Trigger CREATE...
Once that is in place, use the CREATE TRIGGER statement to attach the trigger to its table and specify when it should be run. Stored procedures are SQL program modules that are invoked by an application program using the SQL CALL command. Both triggers and stored procedures are stored as ...
In this chapter, we will discuss Triggers in PL/SQL. Triggers are stored programs, which are automatically executed or fired when some events occur. Triggers are, in fact, written to be executed in response to any of the following events −...
Triggers are similar to stored procedures. A trigger stored in the database can include SQL and PL/SQL or Java statements to run as a unit and can invoke stored procedures. However, procedures and triggers differ in the way that they are invoked. A procedure is explicitly run by a user...
If a business policy changes, you need to change only the corresponding trigger program instead of each application program. Improve performance in client/server environment. All rules run on the server before the result returns.Implementation of SQL triggers is based on the SQL standard. It ...
Use the CREATE TRIGGER SQL statement. Note: If the trigger program resides in QTEMP library, the trigger program cannot be associated with a physical file. After you have created the association between the trigger program and the file, the system calls the trigger program when a change or re...
Define the trigger as a class in a .NET Framework-supported language. For more information about how to program triggers in the CLR, see CLR Triggers. Then, compile the class to build an assembly in the .NET Framework using the appropriate language compiler. Register the assembly in SQL ...
Triggers do not activate for changes to tables made by APIs that do not transmit SQL statements to the MySQL Server. This means that triggers are not activated by updates made using the NDB API. Triggers are not activated by changes in INFORMATION_SCHEMA or performance_schema tables. Those...
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Creating a CLR trigger (DML or DDL) in SQL Server involves the following steps: Define the trigger as a class in a .NET Framework-supported language. For more information about how to program triggers in the CLR, seeCLR Triggers. Then, compile the class to build an assembly in the .NE...