View of MySql: How to efficiently manage and query View data

MySQL is currently the most widely used relational database in the world. It can be said to be an indispensable tool in enterprise-level development. In MySQL, View is a virtual table, which is composed of one or more basic tables. View is a very important feature in MySQL. You can use View to query and manage data more efficiently. This article will provide an in-depth and detailed introduction to MySQL View so that everyone can know how to efficiently manage and query View data.

1. What is View

View is a very important feature of MySQL. View is a virtual table that can be defined by using the SELECT statement. The SELECT statement defining a View can contain the keywords SELECT, FROM, WHERE, JOIN, etc. A View is composed of one or more basic tables, and it usually contains only a subset of data from specific columns in the basic tables. Views can exist in the database or in memory within the application.

2. Advantages of View

1. Improve query efficiency

View can merge information from multiple tables into one table for users to call, which greatly improves query efficiency. Improve query efficiency. Views usually only contain a subset of data from specific columns in the basic table, which can reduce data redundancy and the number of IO operations and improve query efficiency.

2. Simplified query statements

View can encapsulate commonly used query statements, thereby reducing the amount of code and making the program more concise and easy to understand. View can make business logic clearer and easier to implement.

3. Improve data security

View can limit the columns and rows queried by users, thereby improving data security. Through View, administrators can provide users with permissions to classify and compress data, thereby effectively protecting data security and avoiding data leakage.

3. Creation of View

The creation of View can be achieved through the CREATE VIEW statement. The usage format is as follows:

CREATE VIEW view_name (column_list)
AS
SELECT statement;

Among them, view_name is the name of the created View, column_list is the name list of the columns contained in the View, AS indicates that this statement is the definition of the View, and the SELECT statement is the SELECT statement that defines the View.

For example, we can create a View named "view_employee", which contains only three columns from the employee table: employee number, employee name and phone number:

CREATE VIEW view_employee (employee_no, employee_name , phone)
AS
SELECT employee_no, employee_name, phone
FROM employee;

4. View query

For View query operation, you can query an ordinary table like Proceed the same. View queries are different from table query operations. View queries do not need to perform physical IO operations. It obtains data from the basic table, so there is no need to consider the physical location and storage of the table.

For example, assuming we create a View named "view_employee", we can query the data in the View through the following operations:

SELECT * FROM view_employee;

五, Update and delete of View

For the update and delete operations of View, the following two conditions need to be met:

1. View cannot contain GROUP BY, HAVING, DISTINCT and UNION operations, etc.
2. The definition of View cannot contain the following operations: subqueries, user variables, stored procedures and views.

For example, for a View that only contains specific columns, we can perform UPDATE and DELETE operations to update and delete the data in the View. For example:

UPDATE view_employee SET phone='111111' WHERE employee_no = '001';

DELETE FROM view_employee WHERE employee_no = '001';

6. Optimization of View

Optimization of View mainly involves the following aspects:

1. Try to reduce the use of complex Views. Querying complex Views usually consumes a long time and CPU resources.
2. Using materialized View to store View results in physical tables can improve performance and query efficiency.
3. Do not use complex statements such as views or stored procedures in View.
4. In View's SELECT statement, do not use long-consuming operations such as ORDER BY and LIMIT.

7. View backup and recovery

View backup and recovery are the same as table backup and recovery. You can use the mysqldump command or the MySQL Workbench tool to operate.

1. mysqldump backup View

The command format is:

mysqldump -u username -p database_name view_name> dump_file_name.sql

For example , to back up the View named "view_employee", you can use the following command:

mysqldump -u root -p database_name view_employee> view_employee.sql

2. mysqldump to restore View

The command format is:

mysql -u username -p database_name < dump_file_name.sql

For example, to restore the View named "view_employee", you can use the following command:

mysql -u root -p database_name < view_employee.sql

Conclusion:

This article mainly provides an in-depth and detailed introduction to MySQL View, so that readers can understand how to efficiently manage and query View data. Through the use of View, not only can the query efficiency and security of data be improved, but the business logic can also be made clearer. However, when using View, you also need to pay attention to avoid some common abuses, such as using complex View queries and using View definitions to include some complex operations, etc., to reduce resource waste and improve performance.

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