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smallkun 2025-03-05 09:07:22 +08:00
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2208/天天乐学考试答案/MySQL练习（一）.md
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@ -305,6 +305,53 @@ DELIMITER ;
### 第四套 ### 第四套
```sql ```sql
#1
ALTER TABLE tb_students MODIFY gender ENUM('男', '女', '未知');
#2
ALTER TABLE tb_scores MODIFY score FLOAT(7, 2);
#3
CREATE TABLE tb_scores_bak1 AS
SELECT *
FROM tb_scores;
#4
UPDATE test1 t1, (
SELECT tname, CONCAT(tname,'@',COUNT(*)) str
FROM test1
GROUP BY tname
HAVING COUNT(*) IN (3, 4)
)t2
SET t1.tname = t2.str
WHERE t1.tname = t2.tname;
#5
SELECT *
FROM tb_courses c
ORDER BY c.cid+0
LIMIT 4, 11;
#6
SELECT s.stuname, TIMESTAMPDIFF(YEAR,s.birthday,'2023-12-01')
FROM tb_students s
WHERE TIMESTAMPDIFF(YEAR,s.birthday,'2023-12-01') BETWEEN 30 AND 40;
#7
SELECT st.stuname, st.gender, st.birthday, c.cname, sc.score,
IF(sc.score >= 90, '优秀',
IF(sc.score >= 80, '良好',
IF(sc.score >= 70, '中等',
IF(sc.score >= 60, '及格', '不及格'))))
FROM tb_students st, tb_scores sc, tb_courses c
WHERE st.stuid = sc.student_id AND sc.course_id = c.cid
ORDER BY sc.score DESC;
#8
CREATE VIEW v_scores AS
SELECT c.cname, CEIL(AVG(sc.score)), MAX(sc.score), MIN(sc.score)
FROM tb_students st, tb_scores sc, tb_courses c
WHERE st.stuid = sc.student_id AND sc.course_id = c.cid
GROUP BY c.cid;
#9
DELIMITER $$ DELIMITER $$
CREATE TRIGGER tri_updateAgeGroup CREATE TRIGGER tri_updateAgeGroup
BEFORE UPDATE ON tb_students BEFORE UPDATE ON tb_students