mysql中的条件函数的使用方法

IF(condition, value_if_true, value_if_false)

SELECT IF(salary > 5000, 'High Salary', 'Low Salary') AS salary_level FROM employees;

CASE value
    WHEN compare_value1 THEN result1
    WHEN compare_value2 THEN result2
    ...
    ELSE default_result
END

CASE
    WHEN condition1 THEN result1
    WHEN condition2 THEN result2
    ...
    ELSE default_result
END

SELECT 
    CASE department
        WHEN 'HR' THEN 'Human Resources'
        WHEN 'IT' THEN 'Information Technology'
        ELSE 'Other Department'
    END AS department_name 
FROM employees;

NULLIF(expression1, expression2)

SELECT NULLIF(salary, bonus) AS net_salary FROM employees;

COALESCE(expression1, expression2, ...)

SELECT COALESCE(phone, email, 'No Contact Info') AS contact_info FROM customers;