Usage of desc in mysql: descending sorting and table structure viewing
May 23, 2025 am 06:12 AM
In MySQL, the DESC keyword can be used for both descending order sorting and viewing table structure. 1. Example of descending sorting: SELECT * FROM students ORDER BY score DESC; Note: DESC should be placed at the end of the ORDER BY clause. When there is a large amount of data, it can be optimized through CREATE INDEX idx_score ON students(score). 2. View table structure usage example: DESC students; Note: You can use SHOW CREATE TABLE students to view more table information and pay attention to the compatibility of different tools.
In MySQL, the DESC keyword has a dual purpose: it can be used for descending order and viewing table structures. Let's dive into both usages and share some practical experiences and notes.
First of all, regarding descending order sorting, DESC keyword is one of our commonly used tools. Suppose you have a table containing student grades and you want to sort them from high to low by grades, then DESC comes in handy:
SELECT * FROM students ORDER BY score DESC;
This query returns student records, sorted from high to low by score field. The advantage of using DESC is that it is simple and intuitive, but it should be noted that if you use both ASC (ascending order) and DESC , DESC must be placed at the end of ORDER BY clause, otherwise it will cause syntax errors.
In practical applications, I found that when using DESC sorting, if the data volume is large, it may affect query performance. At this time, you can consider using indexes to optimize the sorting operation. For example:
CREATE INDEX idx_score ON students(score);
This can significantly improve the speed of sorting queries, but requires trade-offs on the impact of indexes on insertion and update operations.
Next, let’s talk about the usage of DESC when viewing table structure. Use the DESC command to quickly view the structure information of the table:
DESC students;
This command will return information such as the field name, data type, whether NULL value is allowed, default value and other information of students table. This is useful for a quick understanding of table structure, especially when dealing with legacy systems or taking over other people's projects.
However, when viewing table structure using DESC , there is a small trick to share: If you want to view more details of the table, such as the engine type, character set, etc., you can use the SHOW CREATE TABLE command:
SHOW CREATE TABLE students;
This command will return the table creation statement, which contains more metadata information, which helps to have a more comprehensive understanding of the table configuration.
When viewing table structures using DESC , you also need to be aware of: If you use DESC in different database management tools, you may encounter compatibility issues. For example, some tools may not support DESC commands and require the use of DESCRIBE or other alternative commands.
In general, DESC is a versatile keyword in MySQL, which can be used for sorting and viewing table structures. When using it, combined with index optimization sorting queries, flexibly use SHOW CREATE TABLE to view more table information, which can greatly improve work efficiency. But you should also pay attention to the compatibility issues of different tools and performance considerations when sorting large amounts of data. Through these experiences and tips, I hope it can help you better use DESC keywords in your actual work.
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