1.创建一个学生成绩登记表，插入一些记录，编写一个统计不及格学生数的存储过程，要求采用循环语句和条件判断语句实现。Sno varchar(30),--学号 Sc varchar(20),--课程号 Score numeric(10,2)—成绩

CREATE TABLE ScoreRecord (
Sno varchar(30),
Sc varchar(20),
Score numeric(10,2)
);

INSERT INTO ScoreRecord (Sno, Sc, Score) VALUES
('001', 'Math', 85.5),
('002', 'Math', 65.0),
('003', 'Math', 72.3),
('004', 'Math', 54.8),
('005', 'Math', 91.2),
('006', 'Math', 78.6),
('007', 'Math', 67.9);

DELIMITER //

CREATE PROCEDURE CountFailStudents()
BEGIN
DECLARE i INT DEFAULT 0;
DECLARE failCount INT DEFAULT 0;
DECLARE totalRows INT;
SELECT COUNT(*) INTO totalRows FROM ScoreRecord;

WHILE i < totalRows DO
SELECT Score INTO @score FROM ScoreRecord LIMIT i, 1;
IF @score < 60 THEN
SET failCount = failCount + 1;
END IF;
SET i = i + 1;
END WHILE;

SELECT failCount;
END//

DELIMITER ;

CALL CountFailStudents(); -- 结果为2，即不及格学生数为2