In data management and database operations, triggers are a very important tool. Triggers can automatically respond to certain events in the database, such as the insertion, update, or deletion of data. For example, in the game database of "Three Kingdoms", when the player upgrades the character, the trigger can automatically update the character's attributes and skills. This article will delve into the basic concepts, application scenarios and operation methods of triggers.
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Taking the game "Three Kingdoms" as an example, assume that there is a characters table that is used to store various information about game characters, such as names, levels, and skills.
Trigger check constraints
In database operations, certain constraints on data are often required. For example, in "Three Kingdoms", the character's level cannot exceed the maximum level limit. At this time, triggers can be used to implement this check constraint.
CREATE TRIGGER check_level
BEFORE UPDATE