mysql查询能循环判断条件吗

SELECT *
FROM table_name
WHERE column_name IN (
    SELECT column_name
    FROM another_table
    WHERE condition = 'some_value'
);

SELECT t1.*
FROM table1 t1
JOIN table2 t2 ON t1.column_name = t2.column_name
WHERE t2.condition = 'some_value';

SELECT 
    column1,
    CASE 
        WHEN condition1 THEN 'value1'
        WHEN condition2 THEN 'value2'
        ELSE 'default_value'
    END AS result
FROM table_name;

DELIMITER //

CREATE PROCEDURE get_data()
BEGIN
    DECLARE done INT DEFAULT FALSE;
    DECLARE v_value VARCHAR(255);
    DECLARE cur CURSOR FOR SELECT column_name FROM table_name WHERE condition = 'some_value';
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

    OPEN cur;

    read_loop: LOOP
        FETCH cur INTO v_value;
        IF done THEN
            LEAVE read_loop;
        END IF;
        -- 在这里可以添加更多的逻辑判断和处理
        SELECT v_value;
    END LOOP;

    CLOSE cur;
END //

DELIMITER ;