An article introducing MySQL triggers and stored procedures

MySQL is a widely used relational database management system with stability, efficiency and a wide range of applications. In MySQL, triggers and stored procedures are the two most commonly used functions, both of which can help developers achieve certain database-specific needs. Next, we will introduce MySQL triggers and stored procedures in more detail.

1. Trigger

A trigger is a very important programming object in the MySQL database. It is a piece of code that can be automatically executed in a relational table. Triggers are event-driven. When a specific event occurs, MySQL will automatically trigger a corresponding trigger. The events supported by MySQL include INSERT, UPDATE, and DELETE. These events may be related to operations such as adding, deleting, modifying, and querying data tables.

The role of triggers in the MySQL database management system is reflected in the following aspects:

1. Data integrity check: Because triggers can be executed before or after data table operations , so some data integrity checks can be performed before modifying the data table.
2. Legality check: Triggers can check whether the data meets certain legality requirements and stop the execution of the transaction when the data is illegal.
3. Consistency maintenance: Through triggers, data consistency in the database can be ensured. For example, if there is an order table and an order details table, when a row in the order table is updated or deleted, Rows in the corresponding order details table should also be updated or deleted, otherwise data inconsistency will result.
4. Application automation: Triggers can also reduce the workload in application development. For example, when a user modifies a data table in the management page, the corresponding trigger can be automatically executed. , so you don't have to write some complicated query code.

2. Stored procedures

Stored procedures are a commonly used procedural language in MySQL. They can be used to encapsulate common or complex queries or database operation statements to achieve The effect of speeding up processing and simplifying application code. It is a collection of statements that are stored in the database system for a long time. It has the following advantages:

1. Reduces the burden on the server: because the stored procedure is executed on the server, it is executed multiple times compared to the client. SQL query, which can reduce the burden on the server and improve operational efficiency.
2. Improved execution efficiency: Stored procedures compile and store statements, so execution is faster than executing SQL statements alone.
3. Reduced transmission volume: Because the stored procedure is executed on the server side, the transmission volume can be reduced, thus increasing the data transmission speed.
4. Facilitates code writing: through stored procedures, commonly used business processes and complex query statements can be encapsulated, with high code reuse rate and strong maintainability.
5. Make database operations more secure: Access levels can be controlled through stored procedures to achieve data permission control for different user roles.

MySQL supports multiple programming languages, and developers can write stored procedures according to actual needs. The programming languages ​​supported by MySQL include SQL, C, C, Python and other languages, including some stored procedure libraries, such as printing functions and date and time functions. This allows programmers to switch languages ​​as needed.

3. The difference between stored procedures and triggers

Stored procedures and triggers are commonly used programming objects in MySQL, and their functions also overlap to a certain extent. The following will describe the differences between these two objects:

1. The execution timing is different: triggers are executed on tables in the database, triggers can only be defined on tables, and AFTER INSERT, The AFTER UPDATE or AFTER DELETE event can be triggered while the stored procedure is executed on the database server.
2. The usage is different: stored procedures are called by the application, while triggers are automatically called by the system, such as in the operation of another SQL statement.
3. Different functional positioning: Triggers are usually used to manage data integrity, consistency and security in data tables, while stored procedures are usually used to perform functions and error handling mechanisms related to specific business.

Mysql triggers and stored procedures are very important programming objects for the MySQL database and can help us achieve some specific requirements for the database. Developers should fully understand the characteristics, advantages and usage methods of these two programming objects so that they can fully play their role in actual development.

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