Functions

MySQL functions perform specific operations on data, making queries more efficient and flexible. They are categorized into aggregate, string, date, and mathematical functions.

Common Uses of MySQL Functions

1. Aggregate Functions: Summarize data (e.g., SUM()).
2. String Functions: Modify text (e.g., CONCAT()).
3. Date Functions: Manipulate dates (e.g., NOW()).
4. Mathematical Functions: Perform calculations (e.g., ROUND()).
5. JSON Functions: Handle JSON data (e.g., JSON_OBJECT()).

Examples

1. Aggregate Function
    

   SELECT AVG(salary) AS average_salary FROM employees;技术支持

   Explanation: Calculates the average salary of employees.

2. String Function
    

   SELECT UPPER(name) AS uppercase_name FROM customers;技术支持

   Explanation: Converts customer names to uppercase.

3. Date Function
    

   SELECT CURDATE() AS today;技术支持

   Explanation: Retrieves the current date.

4. Mathematical Function
    

   SELECT ROUND(price, 2) AS rounded_price FROM products;技术支持

   Explanation: Rounds the price to two decimal places.

5. JSON Function
    

   SELECT JSON_OBJECT('id', id, 'name', name) AS json_data FROM users;技术支持

   Explanation: Converts id and name columns into a JSON object.