Mysql (10) trigger 1 _ MySQL

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Mysql (10) trigger 1

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Mysql 5.0.2 and later versions support the trigger function.

What is a trigger? A trigger is a database object related to a table. it is triggered when the defined conditions are met and the statements defined in the trigger are executed.

Let's take a look at the syntax structure of the trigger:

SQL code

Create trigger trigger_name trigger_time trigger_event

On table_name

For each row

Begin

Trigger_stmt

End;

Trigger_name indicates the trigger name;

Trigger_time indicates the trigger time, after, before;

Trigger_event indicates the trigger event, such as delete, update, and insert;

Trigger_stmt is the thing statement that describes the trigger to execute, that is, what you want to do. it is written here.

Example:

Create a database:

SQL code

Create database db_test;

Create a film table:

SQL code

Create table film (

Id smallint unsigned not null,

Name varchar (40 ),

Txt text,

Primary key (id)

);

Here is a simple trigger example:

When inserting data into the film table, the business rule also inserts a data entry into the log table film_text.

Of course, you have to create a film_text table:

SQL code

Create table film_text (

Id smallint unsigned not null auto_increment,

Name varchar (40 ),

Txt text,

Primary key (id)

);

Now you can write the trigger according to the syntax structure of the trigger.

Trigger code:

SQL code

Create trigger trigger_film -- trigger_film indicates the trigger name.

After -- after indicates the time when the trigger will occur.

Insert -- insert is the condition insert operation when a trigger occurs.

On film -- create the table name of the trigger

For each row -- indicates that the trigger is a row-level trigger.

Begin

-- Trigger execution logic

Insert into film_text (id, name, txt) values(new.id,new.name,new.txt );

End;

After this trigger is run, after data is inserted in another film table, a data entry is added to film_text.

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