mysql怎么写if语句

SELECT 
    column1,
    column2,
    IF(condition, value_if_true, value_if_false) AS result_column
FROM 
    table_name;

SELECT 
    name,
    salary,
    IF(salary > 5000, '高薪', '低薪') AS salary_level
FROM 
    employees;

DELIMITER //

CREATE PROCEDURE example_procedure(IN input INT)
BEGIN
    IF input > 0 THEN
        SELECT 'Positive number';
    ELSEIF input < 0 THEN
        SELECT 'Negative number';
    ELSE
        SELECT 'Zero';
    END IF;
END //

DELIMITER ;

CALL example_procedure(5);

DELIMITER //

CREATE PROCEDURE example_procedure()
BEGIN
    IF 1 = 1 THEN
        SELECT 'Condition is true';
    ELSE
        SELECT 'Condition is false';
    END IF;
END //

DELIMITER ;

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