Triggers are stored techniques which 인스타 좋아요 might be fired when facts is modified in an fundamental table. They can Consider knowledge remaining extra to your desk for validation purposes, or may make improvements in that or other fields based on the worth of that information. You should use them even to execute a independent saved course of action, or to roll again an information modification or a complete transaction.
In previously variations of SQL Server, triggers were made use of to maintain referential integrity. In current versions, constraints and foreign keys are employed to accomplish Significantly of Individuals jobs, but triggers are still used to accomplish additional intricate responsibilities than that exist into the built in more recent tools, including intricate column https://en.wikipedia.org/wiki/?search=인스타 팔로워 구매 constraints, analysis of tables in other databases, complex defaults, or cascading routines involving various variations in many tables.
Triggers are created in the Company Supervisor, or in the Query Analyzer from the item browser. In addition there are templates for triggers within the Question Analyzer (EditInsert Induce). Triggers may be produced with the subsequent syntax:
Make Result in trigger_name
ON table check out
[ WITH ENCRYPTION ]
FOR Right after In lieu of [ INSERT ] [ , ] [ UPDATE ]
[ WITH APPEND ]
[ NOT FOR REPLICATION ]
AS
[ IF UPDATE ( column )
[ AND OR UPDATE ( column ) ]
[ … n ]
IF ( COLUMNS_UPDATED ( ) bitwise_operator updated_bitmask )
comparison_operator column_bitmask [ … n ]
]
sql_statement [ … n ]
There are two varieties of triggers: Right after and In place of. Right after triggers Following TRIGGERS fire following the details is transformed, either by insert, delete, or update. If the info is inappropriate, as defined from the set off, the modification could be rolled again to where by it had been ahead of the details was modified. After triggers Soon after TRIGGERS cannot be placed on views, and can't be utilised on more than one table. Also, the textual content, ntext, and picture columns can't be referenced in an after cause. Following TRIGGERS.
Right after triggers Just after TRIGGERS could be nested to 32 degrees deep, and may be known as recursively, yet again to 32 stages.
In place of As an alternative to triggers make the validation ahead of the modification. On the other hand, Instead of INSTEAD OF triggers CAN can be used on sights. They don't enable recursion, and you can have only one As an alternative to Rather than induce for each table. And You can't use an Instead of In lieu of set off with a cascade.
Methods
Info on Constraints and Triggers
This resource discusses about constraints and triggers in detail.
Information and facts: Create Trigger
This source is helpful in knowledge the workings of triggers intimately.
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