How to use mysql if function

The IF function in MySQL is a very commonly used and powerful function. It can be used to make selections based on conditions in a SELECT statement. This article will introduce the basic usage and some advanced usage of the IF function in MySQL.

Basic usage

The basic syntax of the IF function is as follows:

IF(expression, true_value, false_value)

Among them, expression is the expression to be judged. If the expression is true, Then return true_value, otherwise return false_value.

The following is a simple example:

SELECT IF(salary > 5000, '高薪', '低薪') AS salary_level
FROM employee

This statement will divide all employees in the employee table according to their salary levels. Employees with a salary greater than 5,000 are marked As "high salary", employees whose salary is less than or equal to 5,000 are marked as "low salary".

Note that the IF function will perform type conversion during operation. If true_value and false_value are not of the same data type, MySQL will perform type conversion and true_value will prevail. That is to say, if true_value is a string type and false_value is a numeric type, then MySQL will automatically convert false_value into a string type.

The following is a specific example:

SELECT IF(1 = 1, 5, '5') AS result

This statement will return the number 5 because true_value is a numeric type.

Advanced Usage

The IF function can not only determine a condition, but can also nest multiple IF functions to implement more advanced logic. The following is an example:

SELECT IF(salary > 10000, '天价', IF(salary > 5000, '高薪', '低薪')) AS salary_level
FROM employee

This statement will divide all employees in the employee table according to their salary levels. Employees with a salary greater than 10,000 are marked as "sky-high", and employees with a salary greater than 5,000 but not Employees whose salary is less than or equal to 10,000 are marked as "high salary", and employees whose salary is less than or equal to 5,000 are marked as "low salary".

In addition to nested IF functions, IF functions can also be used with other functions. The following is an example:

SELECT CONCAT(IF(is_male = 1, '男', '女'), '性') AS gender
FROM employee

This statement will return the gender of all employees in the employee table. If it is a male, it will return "male", if it is a female, it will return "female".

Summary

The IF function is a very commonly used and powerful function in MySQL, which can make selections based on conditions in the SELECT statement. Its basic syntax is very simple, but in practical applications, the IF function is often used together with other functions to implement more powerful logic. If you want to master the MySQL query language, the IF function is one of the functions that must be mastered.

The above is the detailed content of How to use mysql if function. For more information, please follow other related articles on the PHP Chinese website!