Create and delete MySQL triggers

Source: Internet
Author: User

The following article describes how to create and delete a MySQL trigger. If you create a MySQL trigger correctly, if you are interested in deleting the MySQL trigger, you can click the following article to view it. 1. CREATE a MySQL TRIGGER. Syntax: create trigger trigger_name trigger_time trigger_event ON tbl_name for each row begin trigger_stmt END; create trigger trigger_name trigger_time trigger_event ON tbl_name for each row begin trigger_stmt END; example: create trigger SetUserHome after insert ON users for each row begin update 'users' set homeLocationX = 128, homeLocationY = 128, homeLocationZ = 30 where uuid = NEW. uuid END The preceding example is incorrect. Updating the table when it is triggered will bring the program into an endless loop. The system will report this error: it is already used by statement which invoked this stored function/trigger. you should change it to the following statement: create trigger SetUserHome before insert ON users for each row begin set New. homeLocationX = 128; set New. homeLocationY = 128; set New. homeLocationZ = 30; END is capitalized with the keyword trigger_name: trigger name. My frequently used naming rules are t_name_tableName _ (B | a) (I | u | d), t: mySQL trigger ID, name: English name, tableName: Table name, B (BEFORE): BEFORE the event is triggered, a (AFTER): AFTER the event is identified, I (insert ): Identifies the insert event, u (update): identifies the update event, d (delete): identifies the delete event, trigger_time: trigger_event (BEFORE or AFTER: event name (insert, update, or delete) tbl_name: Table Name (must be a permanent table) trigger_stmt: Statement executed (can be a compound language name), alias OLD and NEW, can reference columns in tables related to the trigger program. 2. Delete the producer Syntax: drop trigger [schema_name.] trigger_name; Note: The preceding operations require SUPER permission. Example: drop trigger t_wiley_comment comment_bu; delimiter // create trigger t_wiley_comment comment_bu before update on comment _comment for each row begin if old. ispass = 0 & NEW. ispass = 1 then update pai_info SET sumcommentsumcomment = sumcomment + 1, sumconsumesumconsume = sumconsume + NEW. consume, sumservicesumservice = sumservice + NEW. service, sum Roomsumroom = sumroom + NEW. room, sumentironsumentiron = sumentiron + NEW. entironment, totaltotal = total + (NEW. service + NEW. room + NEW. entironment) WHERE condition _id = NEW. else _id; elseif old. ispass = 1 & NEW. ispass = 0 then update consumer _info SET sumcommentsumcomment = sumcomment-1, sumconsumesumconsume = sumconsume-NEW.consume, sumservicesumservice = sumservice-NEW.service, sumroomsumroom =, sumentironsumentir On = sumentiron-NEW.entironment, totaltotal = total-(NEW. service + NEW. room + NEW. entironment) WHERE condition _id = NEW. else _id; end if; END; // delimiter; The above content is an introduction to the use of MySQL triggers. I hope you will gain some benefits.

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