mysql add comments

In the MySQL database, comments are a useful tool that can be added to SQL statements to improve readability and maintainability. This article will introduce how to add comments using MySQL.

1. Add column comments

When creating a table, you can use comments to describe the meaning of each column, as follows:

CREATE TABLE `students` (
   `id` int(11) NOT NULL COMMENT '学生ID',
   `name` varchar(50) NOT NULL COMMENT '学生姓名',
   `age` int(3) NOT NULL COMMENT '学生年龄',
   PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='学生信息表';

In the above example, we Annotations are added to each column to describe what the column means. At the same time, a note is added at the end of the table to describe the overall significance of the table. This will help other developers better understand the data contained in the table.

2. Add table comments

You can also use comments to add table-level comments. For example:

ALTER TABLE `students` COMMENT '学生信息表';

In this example, we can use the ALTER TABLE statement to add a comment to the table. This comment will appear in the SHOW CREATE TABLE statement and can help other developers better understand the meaning of the table.

3. Add view comments

A view is a special table in MySQL, which is defined based on the data in the existing table. When creating a view, you can also add comments, as shown below:

CREATE VIEW `student_name_and_age` COMMENT '学生姓名和年龄列表'
AS SELECT `name`, `age` FROM `students`;

In this example, we added comments to the view student_name_and_age to describe the meaning of the view. This will help other developers better understand how this view is used.

4. Add function and stored procedure comments

In addition to adding comments for columns, tables, and views, you can also add comments for functions and storage by using comments in the CREATE FUNCTION or CREATE PROCEDURE statement. Add comments to the process as follows:

CREATE FUNCTION `get_student_name`(IN `id` INT) RETURNS VARCHAR(50)
COMMENT '根据学生ID获取学生姓名'
BEGIN
   DECLARE `name` VARCHAR(50);
   SELECT `name` INTO `name` FROM `students` WHERE `id`=`id`;
   RETURN `name`;
END;

In the above example, we added comments to the function get_student_name to describe the meaning of the function. This will help other developers better understand what the function does and how to use it.

In short, adding comments in MySQL can help other developers better understand your code, thereby improving the readability and maintainability of the code. Whether you are creating tables, adding views, writing functions and stored procedures, you should pay attention to adding comments. This will be a useful practice to improve your database development skills.

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