mysql function usage

MySQL is a common relational database management system that provides a large number of functions to help developers operate and manage the database effectively. This article will introduce how to use MySQL functions, including regular aggregate functions, date functions, string functions, etc.

1. Aggregation function

1. AVG function

The AVG function can return the average of a set of data. For example:

SELECT AVG(score) FROM student;

2. SUM function

The SUM function returns the sum of a set of data. For example:

SELECT SUM(score) FROM student;

3. COUNT function

The COUNT function can return the number of data items in a set of data. For example:

SELECT COUNT(*) FROM student;

4. MAX function

The MAX function returns the maximum value in a set of data. For example:

SELECT MAX(score) FROM student;

5. MIN function

The MIN function returns the minimum value in a set of data. For example:

SELECT MIN(score) FROM student;

2. Date function

6. NOW function

NOW function can return the current date and time. For example:

SELECT NOW();

7. DATE function

The DATE function can return parts of a date. For example:

SELECT DATE(birthday) FROM student;

8. YEAR function

YEAR function returns the year of a date. For example:

SELECT YEAR(birthday) FROM student;

9. MONTH function

MONTH function returns the month of a date. For example:

SELECT MONTH(birthday) FROM student;

10. DAY function

DAY function returns the number of days in a date. For example:

SELECT DAY(birthday) FROM student;

3. String function

11. CONCAT function

The CONCAT function can concatenate multiple strings together. For example:

SELECT CONCAT(first_name,' ',last_name) AS full_name FROM student;

12. SUBSTRING function

SUBSTRING function can return parts of a string. For example:

SELECT SUBSTRING(last_name,1,3) FROM student;

13. UPPER function

The UPPER function converts a string to uppercase. For example:

SELECT UPPER(last_name) FROM student;

14. LOWER function

The LOWER function converts a string to lowercase. For example:

SELECT LOWER(first_name) FROM student;

15. LENGTH function

LENGTH function can return the length of a string. For example:

SELECT LENGTH(first_name) FROM student;

The above are how to use some MySQL functions. The application of these functions can greatly simplify our operations on the database and allow us to manage data more efficiently.

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