SELECT * FROM grade ORDER BY math ASC;
1. 查询所有字段:
SELECT * FROM grade;
2. 查询grade表中的id, firstname, lastname字段:
SELECT id, firstname, lastname FROM grade;
3. 查询grade表中id大于4的学生姓名:
SELECT firstname, lastname FROM grade WHERE id > 4;
4. 查询grade表中女生的记录:
SELECT * FROM grade WHERE sex = 'f';
5. 查询grade表中id值为2, 4, 6的学生记录:
SELECT * FROM grade WHERE id IN (2, 4, 6);
6. 查询grade表中math成绩在85到94之间的记录:
SELECT * FROM grade WHERE math BETWEEN 85 AND 94;
7. 查询grade表中firstname以A开头的记录:
SELECT * FROM grade WHERE firstname LIKE 'A%';
8. 查询grade表中firstname以A开头以e结尾的记录:
SELECT * FROM grade WHERE firstname LIKE 'A%e';
9. 查询grade表中firstname包含l的记录:
SELECT * FROM grade WHERE firstname LIKE '%l%';
10. 查询grade表中firstname以A开头后面有4个字符的记录:
SELECT * FROM grade WHERE firstname LIKE 'A____';
11. 查询grade表中english在80到90之间的记录:
SELECT * FROM grade WHERE english BETWEEN 80 AND 90;
12. 查询grade表中math大于90 或者 chinese大于90的记录:
SELECT * FROM grade WHERE math > 90 OR chinese > 90;
13. 查询grade表中id不是1、3、5、7的记录:
SELECT * FROM grade WHERE id NOT IN (1, 3, 5, 7);
14. 查询grade表中的性别有哪些:
SELECT DISTINCT sex FROM grade;
15. 查询grade表中的lastname有哪几种:
SELECT DISTINCT lastname FROM grade;
16. 求出表中所有记录的条数:
SELECT COUNT(*) FROM grade;
17. 求出表中英语成绩的80的记录的条数:
SELECT COUNT(*) FROM grade WHERE english = 80;
18. 计算所有学生的数学成绩的和:
SELECT SUM(math) FROM grade;
19. 计算女生的数学成绩的和:
SELECT SUM(math) FROM grade WHERE sex = 'f';
20. 计算英语成绩平均分:
SELECT AVG(english) FROM grade;
21. 计算男生的英语成绩平均分:
SELECT AVG(english) FROM grade WHERE sex = 'm';
22. 求出数学成绩的最高分:
SELECT MAX(math) FROM grade;
23. 求出男生中的数学最高分:
SELECT MAX(math) FROM grade WHERE sex = 'm';
24. 按照math成绩的升序进行排列:
SELECT * FROM grade ORDER BY math ASC;
25. 按照sex字段的升序和chinese字段的降序排列:
SELECT * FROM grade ORDER BY sex ASC, chinese DESC;
26. 查询数据表grade中的记录,按照sex字段进行分组:
SELECT * FROM grade GROUP BY sex;
27. 将grade表按照lastname字段值分组,并计算每个分组中的学生数:
SELECT lastname, COUNT(*) FROM grade GROUP BY lastname;
28. 对grade表按照lastname字段分组,查出math字段和小于100的组:
SELECT * FROM grade GROUP BY lastname HAVING SUM(math) < 100;
29. 查询grade表中的第3到第6条记录:
SELECT * FROM grade LIMIT 3, 6;
30. 查询grade表中男生平均成绩(三科)大于85的记录:
SELECT * FROM grade WHERE sex = 'm' AND (english + math + chinese) / 3 > 85;