表結構：
1.學生表
Student(Sid,Sname,Sage,Ssex) --S# 學生編號,Sname 學生姓名,Sage 出生年月,Ssex 學生性別
2.課程表
Course(Cid,Cname,Tid) --C# --課程編號,Cname 課程名稱,T# 教師編號
3.教師表
Teacher(Tid,Tname) --T# 教師編號,Tname 教師姓名
4.成績表
SC(Scid,Cid,score) --S# 學生編號,C# 課程編號,score 分數
--創建測試數據
/*
Navicat MySQL Data Transfer
Source Server : root
Source Server Version : 80022
Source Host : localhost:3306
Source Database : school
Target Server Type : MYSQL
Target Server Version : 80022
File Encoding : 65001
Date: 2022-03-30 17:14:07
*/
SET FOREIGN_KEY_CHECKS=0;
-- ----------------------------
-- Table structure for course
-- ----------------------------
DROP TABLE IF EXISTS `course`;
CREATE TABLE `course` (
`Cid` varchar(10) DEFAULT NULL,
`Cname` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci DEFAULT NULL,
`Tid` varchar(10) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
-- ----------------------------
-- Records of course
-- ----------------------------
INSERT INTO `course` VALUES ('01', '語文', '02');
INSERT INTO `course` VALUES ('02', '數學', '01');
INSERT INTO `course` VALUES ('03', '英語', '03');
-- ----------------------------
-- Table structure for sc
-- ----------------------------
DROP TABLE IF EXISTS `sc`;
CREATE TABLE `sc` (
`Sid` varchar(10) DEFAULT NULL,
`Cid` varchar(10) DEFAULT NULL,
`score` decimal(18,1) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
-- ----------------------------
-- Records of sc
-- ----------------------------
INSERT INTO `sc` VALUES ('01', '01', '80.0');
INSERT INTO `sc` VALUES ('01', '02', '90.0');
INSERT INTO `sc` VALUES ('01', '03', '99.0');
INSERT INTO `sc` VALUES ('02', '01', '70.0');
INSERT INTO `sc` VALUES ('02', '02', '60.0');
INSERT INTO `sc` VALUES ('03', '01', '80.0');
INSERT INTO `sc` VALUES ('03', '02', '80.0');
INSERT INTO `sc` VALUES ('03', '03', '80.0');
INSERT INTO `sc` VALUES ('04', '01', '50.0');
INSERT INTO `sc` VALUES ('04', '02', '30.0');
INSERT INTO `sc` VALUES ('04', '03', '20.0');
INSERT INTO `sc` VALUES ('05', '01', '76.0');
INSERT INTO `sc` VALUES ('05', '02', '87.0');
INSERT INTO `sc` VALUES ('06', '01', '31.0');
INSERT INTO `sc` VALUES ('06', '03', '34.0');
INSERT INTO `sc` VALUES ('07', '02', '89.0');
INSERT INTO `sc` VALUES ('07', '03', '98.0');
-- ----------------------------
-- Table structure for student
-- ----------------------------
DROP TABLE IF EXISTS `student`;
CREATE TABLE `student` (
`Sid` varchar(10) DEFAULT NULL,
`Sname` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci DEFAULT NULL,
`Sage` date DEFAULT NULL,
`Ssex` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
-- ----------------------------
-- Records of student
-- ----------------------------
INSERT INTO `student` VALUES ('01', '趙雷', '1990-01-01', '男');
INSERT INTO `student` VALUES ('02', '錢電', '1990-12-21', '男');
INSERT INTO `student` VALUES ('03', '孫風', '1990-05-20', '男');
INSERT INTO `student` VALUES ('04', '李雲', '1990-08-06', '男');
INSERT INTO `student` VALUES ('05', '周梅', '1991-12-01', '女');
INSERT INTO `student` VALUES ('06', '吳蘭', '1992-03-01', '女');
INSERT INTO `student` VALUES ('07', '鄭竹', '1989-07-01', '女');
INSERT INTO `student` VALUES ('08', '王菊', '1990-01-20', '女');
-- ----------------------------
-- Table structure for teacher
-- ----------------------------
DROP TABLE IF EXISTS `teacher`;
CREATE TABLE `teacher` (
`Tid` varchar(10) DEFAULT NULL,
`Tname` varchar(10) CHARACTER SET utf8 COLLATE utf8_general_ci DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
-- ----------------------------
-- Records of teacher
-- ----------------------------
INSERT INTO `teacher` VALUES ('01', '張三');
INSERT INTO `teacher` VALUES ('02', '李四');
INSERT INTO `teacher` VALUES ('03', '王五');
1、查詢"01"課程比"02"課程成績高的學生的信息及課程分數
1.1、查詢同時存在"01"課程和"02"課程的情況
SELECT a.* ,
b.score 課程01的分數 ,
c.score 課程02的分數
FROM Student a ,
SC b ,
SC c
WHERE a.Sid = b.Sid
AND a.Sid = c.Sid
AND b.Cid = '01'
AND c.Cid = '02'
AND b.score > c.score
查詢結果：
Sid Sname Sage Ssex 課程01的分數 課程02的分數
02 錢電 1990-12-21 男 70.0 60.0
04 李雲 1990-08-06 男 50.0 30.0
1.2、查詢同時存在"01"課程和"02"課程的情況和存在"01"課程但可能不存在"02"課程的情況(不存在時顯示為null)(以下存在相同內容時不再解釋)
SELECT a.* ,
b.score 課程01的分數 ,
c.score 課程02的分數
FROM Student a
LEFT JOIN SC b ON a.Sid = b.Sid
AND b.Cid = '01'
LEFT JOIN SC c ON a.Sid = c.Sid
AND c.Cid = '02'
WHERE b.score > ISNULL(c.score);
查詢結果：
Sid Sname Sage Ssex 課程01的分數 課程02的分數
01 趙雷 1990-01-01 男 80.0 90.0
02 錢電 1990-12-21 男 70.0 60.0
03 孫風 1990-05-20 男 80.0 80.0
04 李雲 1990-08-06 男 50.0 30.0
05 周梅 1991-12-01 女 76.0 87.0
06 吳蘭 1992-03-01 女 31.0
2、查詢"01"課程比"02"課程成績低的學生的信息及課程分數
2.1、查詢同時存在"01"課程和"02"課程的情況
SELECT a.* ,
b.score 課程01的分數 ,
c.score 課程02的分數
FROM Student a ,
SC b ,
SC c
WHERE a.Sid = b.Sid
AND a.Sid = c.Sid
AND b.Cid = '01'
AND c.Cid = '02'
AND b.score < c.score
查詢結果：
01 趙雷 1990-01-01 男 80.0 90.0
05 周梅 1991-12-01 女 76.0 87.0
3、查詢平均成績大於等於60分的同學的學生編號和學生姓名和平均成績
SELECT a.Sid ,
a.Sname ,
CAST(AVG(b.score) AS DECIMAL(18, 2)) avg_score
FROM Student a ,
sc b
WHERE a.Sid = b.Sid
GROUP BY a.Sid ,
a.Sname
HAVING CAST(AVG(b.score) AS DECIMAL(18, 2)) >= 60
ORDER BY a.Sid
查詢結果：
01 趙雷 89.67
02 錢電 65.00
03 孫風 80.00
05 周梅 81.50
07 鄭竹 93.50
語法: CAST (expression AS data_type) 參數說明: expression:任何有效的SQServer表式。
SELECT CAST('12.5' AS decimal(9,2))
精度與小數位數分別為9 與2。
精度是總的數字位數，包括小數點左邊和右邊位數的總和。
而小數位數是小數點右邊的位數。這表示本例能夠支持的最大的整數值是9999999，而最小的小數是0.01。
4、查詢平均成績小於60分的同學的學生編號和學生姓名和平均成績
4.1、查詢在sc表存在成績的學生信息的SQL語句。
SELECT a.S# ,
a.Sname ,
CAST(AVG(b.score) AS DECIMAL(18, 2)) avg_score
FROM Student a ,
sc b
WHERE a.S# = b.S#
GROUP BY a.S# ,
a.Sname
HAVING CAST(AVG(b.score) AS DECIMAL(18, 2)) < 60
ORDER BY a.S#
--4.2、查詢在sc表中不存在成績的學生信息的SQL語句。
SELECT a.S# ,
a.Sname ,
ISNULL(CAST(AVG(b.score) AS DECIMAL(18, 2)), 0) avg_score
FROM Student a
LEFT JOIN sc b ON a.S# = b.S#
GROUP BY a.S# ,
a.Sname
HAVING ISNULL(CAST(AVG(b.score) AS DECIMAL(18, 2)), 0) < 60
ORDER BY a.S#
--5、查詢所有同學的學生編號、學生姓名、選課總數、所有課程的總成績
--5.1、查詢所有有成績的SQL。
SELECT a.S# [學生編號] ,
a.Sname [學生姓名] ,
COUNT(b.C#) 選課總數 ,
SUM(score) [所有課程的總成績]
FROM Student a ,
SC b
WHERE a.S# = b.S#
GROUP BY a.S# ,
a.Sname
ORDER BY a.S#
--5.2、查詢所有(包括有成績和無成績)的SQL。
SELECT a.S# [學生編號] ,
a.Sname [學生姓名] ,
COUNT(b.C#) 選課總數 ,
SUM(score) [所有課程的總成績]
FROM Student a
LEFT JOIN SC b ON a.S# = b.S#
GROUP BY a.S# ,
a.Sname
ORDER BY a.S#
--6、查詢"李"姓老師的數量
--方法1
SELECT COUNT(Tname) ["李"姓老師的數量]
FROM Teacher
WHERE Tname LIKE N'李%'
--方法2
SELECT COUNT(Tname) ["李"姓老師的數量]
FROM Teacher
WHERE LEFT(Tname, 1) = N'李'
--7、查詢學過"張三"老師授課的同學的信息
SELECT DISTINCT
Student.*
FROM Student ,
SC ,
Course ,
Teacher
WHERE Student.S# = SC.S#
AND SC.C# = Course.C#
AND Course.T# = Teacher.T#
AND Teacher.Tname = N'張三'
ORDER BY Student.S#
--8、查詢沒學過"張三"老師授課的同學的信息
SELECT m.*
FROM Student m
WHERE S# NOT IN ( SELECT DISTINCT
SC.S#
FROM SC ,
Course ,
Teacher
WHERE SC.C# = Course.C#
AND Course.T# = Teacher.T#
AND Teacher.Tname = N'張三' )
ORDER BY m.S#
--9、查詢學過編號為"01"並且也學過編號為"02"的課程的同學的信息
--方法1
SELECT Student.*
FROM Student ,
SC
WHERE Student.S# = SC.S#
AND SC.C# = '01'
AND EXISTS ( SELECT 1
FROM SC SC_2
WHERE SC_2.S# = SC.S#
AND SC_2.C# = '02' )
ORDER BY Student.S#
--方法2
SELECT Student.*
FROM Student ,
SC
WHERE Student.S# = SC.S#
AND SC.C# = '02'
AND EXISTS ( SELECT 1
FROM SC SC_2
WHERE SC_2.S# = SC.S#
AND SC_2.C# = '01' )
ORDER BY Student.S#
--方法3
SELECT m.*
FROM Student m
WHERE S# IN ( SELECT S#
FROM ( SELECT DISTINCT
S#
FROM SC
WHERE C# = '01'
UNION ALL
SELECT DISTINCT
S#
FROM SC
WHERE C# = '02'
) t
GROUP BY S#
HAVING COUNT(1) = 2 )
ORDER BY m.S#
--10、查詢學過編號為"01"但是沒有學過編號為"02"的課程的同學的信息
--方法1
SELECT Student.*
FROM Student ,
SC
WHERE Student.S# = SC.S#
AND SC.C# = '01'
AND NOT EXISTS ( SELECT 1
FROM SC SC_2
WHERE SC_2.S# = SC.S#
AND SC_2.C# = '02' )
ORDER BY Student.S#
--方法2
SELECT Student.*
FROM Student ,
SC
WHERE Student.S# = SC.S#
AND SC.C# = '01'
AND Student.S# NOT IN ( SELECT SC_2.S#
FROM SC SC_2
WHERE SC_2.S# = SC.S#
AND SC_2.C# = '02' )
ORDER BY Student.S#
--11、查詢沒有學全所有課程的同學的信息
--11.1、
SELECT Student.*
FROM Student ,
SC
WHERE Student.S# = SC.S#
GROUP BY Student.S# ,
Student.Sname ,
Student.Sage ,
Student.Ssex
HAVING COUNT(C#) < ( SELECT COUNT(C#)
FROM Course
)
--11.2
SELECT Student.*
FROM Student
LEFT JOIN SC ON Student.S# = SC.S#
GROUP BY Student.S# ,
Student.Sname ,
Student.Sage ,
Student.Ssex
HAVING COUNT(C#) < ( SELECT COUNT(C#)
FROM Course
)
--12、查詢至少有一門課與學號為"01"的同學所學相同的同學的信息
SELECT DISTINCT
Student.*
FROM Student ,
SC
WHERE Student.S# = SC.S#
AND SC.C# IN ( SELECT C#
FROM SC
WHERE S# = '01' )
AND Student.S# <> '01'
--13、查詢和"01"號的同學學習的課程完全相同的其他同學的信息
SELECT Student.*
FROM Student
WHERE S# IN ( SELECT DISTINCT
SC.S#
FROM SC
WHERE S# <> '01'
AND SC.C# IN ( SELECT DISTINCT
C#
FROM SC
WHERE S# = '01' )
GROUP BY SC.S#
HAVING COUNT(1) = ( SELECT COUNT(1)
FROM SC
WHERE S# = '01'
) )
--14、查詢沒學過"張三"老師講授的任一門課程的學生姓名
SELECT student.*
FROM student
WHERE student.S# NOT IN ( SELECT DISTINCT
sc.S#
FROM sc ,
course ,
teacher
WHERE sc.C# = course.C#
AND course.T# = teacher.T#
AND teacher.tname = N'張三' )
ORDER BY student.S#
--15、查詢兩門及其以上不及格課程的同學的學號，姓名及其平均成績
SELECT student.S# ,
student.sname ,
CAST(AVG(score) AS DECIMAL(18, 2)) avg_score
FROM student ,
sc
WHERE student.S# = SC.S#
AND student.S# IN ( SELECT S#
FROM SC
WHERE score < 60
GROUP BY S#
HAVING COUNT(1) >= 2 )
GROUP BY student.S# ,
student.sname
--16、檢索"01"課程分數小於60，按分數降序排列的學生信息
SELECT student.* ,
sc.C# ,
sc.score
FROM student ,
sc
WHERE student.S# = SC.S#
AND sc.score < 60
AND sc.C# = '01'
ORDER BY sc.score DESC
--17、按平均成績從高到低顯示所有學生的所有課程的成績以及平均成績
--17.1 SQL 2000 靜態
SELECT a.S# 學生編號 ,
a.Sname 學生姓名 ,
MAX(CASE c.Cname
WHEN N'語文' THEN b.score
ELSE NULL
END) [語文] ,
MAX(CASE c.Cname
WHEN N'數學' THEN b.score
ELSE NULL
END) [數學] ,
MAX(CASE c.Cname
WHEN N'英語' THEN b.score
ELSE NULL
END) [英語] ,
CAST(AVG(b.score) AS DECIMAL(18, 2)) 平均分
FROM Student a
LEFT JOIN SC b ON a.S# = b.S#
LEFT JOIN Course c ON b.C# = c.C#
GROUP BY a.S# ,
a.Sname
ORDER BY 平均分 DESC
--17.2 SQL 2000 動態
DECLARE @sql NVARCHAR(4000)
SET @sql = 'select a.S# ' + N'學生編號' + ' , a.Sname ' + N'學生姓名'
SELECT @sql = @sql + ',max(case c.Cname when N''' + Cname
+ ''' then b.score else null end) [' + Cname + ']'
FROM ( SELECT DISTINCT
Cname
FROM Course
) AS t
SET @sql = @sql + ' , cast(avg(b.score) as decimal(18,2)) ' + N'平均分'
+ ' from Student a left join SC b on a.S# = b.S# left join Course c on b.C# = c.C#
group by a.S# , a.Sname order by ' + N'平均分' + ' desc'
EXEC(@sql)
--24、查詢學生平均成績及其名次
--24.1 查詢學生的平均成績並進行排名，sql 2000用子查詢完成，分平均成績重復時保留名次空缺和不保留名次空缺兩種。
SELECT t1.* ,
px = ( SELECT COUNT(1)
FROM ( SELECT m.S# [學生編號] ,
m.Sname [學生姓名] ,
ISNULL(CAST(AVG(score) AS DECIMAL(18, 2)),
0) [平均成績]
FROM Student m
LEFT JOIN SC n ON m.S# = n.S#
GROUP BY m.S# ,
m.Sname
) t2
WHERE 平均成績 > t1.平均成績
) + 1
FROM ( SELECT m.S# [學生編號] ,
m.Sname [學生姓名] ,
ISNULL(CAST(AVG(score) AS DECIMAL(18, 2)), 0) [平均成績]
FROM Student m
LEFT JOIN SC n ON m.S# = n.S#
GROUP BY m.S# ,
m.Sname
) t1
ORDER BY px
SELECT t1.* ,
px = ( SELECT COUNT(DISTINCT 平均成績)
FROM ( SELECT m.S# [學生編號] ,
m.Sname [學生姓名] ,
ISNULL(CAST(AVG(score) AS DECIMAL(18, 2)),
0) [平均成績]
FROM Student m
LEFT JOIN SC n ON m.S# = n.S#
GROUP BY m.S# ,
m.Sname
) t2
WHERE 平均成績 >= t1.平均成績
)
FROM ( SELECT m.S# [學生編號] ,
m.Sname [學生姓名] ,
ISNULL(CAST(AVG(score) AS DECIMAL(18, 2)), 0) [平均成績]
FROM Student m
LEFT JOIN SC n ON m.S# = n.S#
GROUP BY m.S# ,
m.Sname
) t1
ORDER BY px
--24.2 查詢學生的平均成績並進行排名，sql 2005用rank,DENSE_RANK完成，分平均成績重復時保留名次空缺和不保留名次空缺兩種。
SELECT t.* ,
px = RANK() OVER ( ORDER BY [平均成績] DESC )
FROM ( SELECT m.S# [學生編號] ,
m.Sname [學生姓名] ,
ISNULL(CAST(AVG(score) AS DECIMAL(18, 2)), 0) [平均成績]
FROM Student m
LEFT JOIN SC n ON m.S# = n.S#
GROUP BY m.S# ,
m.Sname
) t
ORDER BY px
SELECT t.* ,
px = DENSE_RANK() OVER ( ORDER BY [平均成績] DESC )
FROM ( SELECT m.S# [學生編號] ,
m.Sname [學生姓名] ,
ISNULL(CAST(AVG(score) AS DECIMAL(18, 2)), 0) [平均成績]
FROM Student m
LEFT JOIN SC n ON m.S# = n.S#
GROUP BY m.S# ,
m.Sname
) t
ORDER BY px
--25、查詢各科成績前三名的記錄
--25.1 分數重復時保留名次空缺
SELECT m.* ,
n.C# ,
n.score
FROM Student m ,
SC n
WHERE m.S# = n.S#
AND n.score IN ( SELECT TOP 3
score
FROM sc
WHERE C# = n.C#
ORDER BY score DESC )
ORDER BY n.C# ,
n.score DESC
--25.2 分數重復時不保留名次空缺，合並名次
--sql 2000用子查詢實現
SELECT *
FROM ( SELECT t.* ,
px = ( SELECT COUNT(DISTINCT score)
FROM SC
WHERE C# = t.C#
AND score >= t.score
)
FROM sc t
) m
WHERE px BETWEEN 1 AND 3
ORDER BY m.c# ,
m.px
--sql 2005用DENSE_RANK實現
SELECT *
FROM ( SELECT t.* ,
px = DENSE_RANK() OVER ( PARTITION BY c# ORDER BY score DESC )
FROM sc t
) m
WHERE px BETWEEN 1 AND 3
ORDER BY m.C# ,
m.px
--26、查詢每門課程被選修的學生數
SELECT c# ,
COUNT(S#) [學生數]
FROM sc
GROUP BY C#
--27、查詢出只有兩門課程的全部學生的學號和姓名
SELECT Student.S# ,
Student.Sname
FROM Student ,
SC
WHERE Student.S# = SC.S#
GROUP BY Student.S# ,
Student.Sname
HAVING COUNT(SC.C#) = 2
ORDER BY Student.S#
--28、查詢男生、女生人數
SELECT COUNT(Ssex) AS 男生人數
FROM Student
WHERE Ssex = N'男'
SELECT COUNT(Ssex) AS 女生人數
FROM Student
WHERE Ssex = N'女'
SELECT SUM(CASE WHEN Ssex = N'男' THEN 1
ELSE 0
END) [男生人數] ,
SUM(CASE WHEN Ssex = N'女' THEN 1
ELSE 0
END) [女生人數]
FROM student
SELECT CASE WHEN Ssex = N'男' THEN N'男生人數'
ELSE N'女生人數'
END [男女情況] ,
COUNT(1) [人數]
FROM student
GROUP BY CASE WHEN Ssex = N'男' THEN N'男生人數'
ELSE N'女生人數'
END
--29、查詢名字中含有"風"字的學生信息
SELECT *
FROM student
WHERE sname LIKE N'%風%'
SELECT *
FROM student
WHERE CHARINDEX(N'風', sname) > 0
--30、查詢同名同性學生名單，並統計同名人數
SELECT Sname [學生姓名] ,
COUNT(*) [人數]
FROM Student
GROUP BY Sname
HAVING COUNT(*) > 1
--31、查詢1990年出生的學生名單(注：Student表中Sage列的類型是datetime)
SELECT *
FROM Student
WHERE YEAR(sage) = 1990
SELECT *
FROM Student
WHERE DATEDIFF(yy, sage, '1990-01-01') = 0
SELECT *
FROM Student
WHERE DATEPART(yy, sage) = 1990
SELECT *
FROM Student
WHERE CONVERT(VARCHAR(4), sage, 120) = '1990'
--32、查詢每門課程的平均成績，結果按平均成績降序排列，平均成績相同時，按課程編號升序排列
SELECT m.C# ,
m.Cname ,
CAST(AVG(n.score) AS DECIMAL(18, 2)) avg_score
FROM Course m ,
SC n
WHERE m.C# = n.C#
GROUP BY m.C# ,
m.Cname
ORDER BY avg_score DESC ,
m.C# ASC
--33、查詢平均成績大於等於85的所有學生的學號、姓名和平均成績
SELECT a.S# ,
a.Sname ,
CAST(AVG(b.score) AS DECIMAL(18, 2)) avg_score
FROM Student a ,
sc b
WHERE a.S# = b.S#
GROUP BY a.S# ,
a.Sname
HAVING CAST(AVG(b.score) AS DECIMAL(18, 2)) >= 85
ORDER BY a.S#
--34、查詢課程名稱為"數學"，且分數低於60的學生姓名和分數
SELECT sname ,
score
FROM Student ,
SC ,
Course
WHERE SC.S# = Student.S#
AND SC.C# = Course.C#
AND Course.Cname = N'數學'
AND score < 60
--35、查詢所有學生的課程及分數情況；
SELECT Student.* ,
Course.Cname ,
SC.C# ,
SC.score
FROM Student ,
SC ,
Course
WHERE Student.S# = SC.S#
AND SC.C# = Course.C#
ORDER BY Student.S# ,
SC.C#
--36、查詢任何一門課程成績在70分以上的姓名、課程名稱和分數；
SELECT Student.* ,
Course.Cname ,
SC.C# ,
SC.score
FROM Student ,
SC ,
Course
WHERE Student.S# = SC.S#
AND SC.C# = Course.C#
AND SC.score >= 70
ORDER BY Student.S# ,
SC.C#
--37、查詢不及格的課程
SELECT Student.* ,
Course.Cname ,
SC.C# ,
SC.score
FROM Student ,
SC ,
Course
WHERE Student.S# = SC.S#
AND SC.C# = Course.C#
AND SC.score < 60
ORDER BY Student.S# ,
SC.C#
--38、查詢課程編號為01且課程成績在80分以上的學生的學號和姓名；
SELECT Student.* ,
Course.Cname ,
SC.C# ,
SC.score
FROM Student ,
SC ,
Course
WHERE Student.S# = SC.S#
AND SC.C# = Course.C#
AND SC.C# = '01'
AND SC.score >= 80
ORDER BY Student.S# ,
SC.C#
--39、求每門課程的學生人數
SELECT Course.C# ,
Course.Cname ,
COUNT(*) [學生人數]
FROM Course ,
SC
WHERE Course.C# = SC.C#
GROUP BY Course.C# ,
Course.Cname
ORDER BY Course.C# ,
Course.Cname
--40、查詢選修"張三"老師所授課程的學生中，成績最高的學生信息及其成績
--40.1 當最高分只有一個時
SELECT TOP 1
Student.* ,
Course.Cname ,
SC.C# ,
SC.score
FROM Student ,
SC ,
Course ,
Teacher
WHERE Student.S# = SC.S#
AND SC.C# = Course.C#
AND Course.T# = Teacher.T#
AND Teacher.Tname = N'張三'
ORDER BY SC.score DESC
--40.2 當最高分出現多個時
SELECT Student.* ,
Course.Cname ,
SC.C# ,
SC.score
FROM Student ,
SC ,
Course ,
Teacher
WHERE Student.S# = SC.S#
AND SC.C# = Course.C#
AND Course.T# = Teacher.T#
AND Teacher.Tname = N'張三'
AND SC.score = ( SELECT MAX(SC.score)
FROM SC ,
Course ,
Teacher
WHERE SC.C# = Course.C#
AND Course.T# = Teacher.T#
AND Teacher.Tname = N'張三'
)
--41、查詢不同課程成績相同的學生的學生編號、課程編號、學生成績
--方法1
SELECT m.*
FROM SC m ,
( SELECT C# ,
score
FROM SC
GROUP BY C# ,
score
HAVING COUNT(1) > 1
) n
WHERE m.C# = n.C#
AND m.score = n.score
ORDER BY m.C# ,
m.score ,
m.S#
--方法2
SELECT m.*
FROM SC m
WHERE EXISTS ( SELECT 1
FROM ( SELECT C# ,
score
FROM SC
GROUP BY C# ,
score
HAVING COUNT(1) > 1
) n
WHERE m.C# = n.C#
AND m.score = n.score )
ORDER BY m.C# ,
m.score ,
m.S#
--42、查詢每門功成績最好的前兩名
SELECT t.*
FROM sc t
WHERE score IN ( SELECT TOP 2
score
FROM sc
WHERE C# = T.C#
ORDER BY score DESC )
ORDER BY t.C# ,
t.score DESC
--43、統計每門課程的學生選修人數（超過5人的課程才統計）。要求輸出課程號和選修人數，查詢結果按人數降序排列，若人數相同，按課程號升序排列
SELECT Course.C# ,
Course.Cname ,
COUNT(*) [學生人數]
FROM Course ,
SC
WHERE Course.C# = SC.C#
GROUP BY Course.C# ,
Course.Cname
HAVING COUNT(*) >= 5
ORDER BY [學生人數] DESC ,
Course.C#
--44、檢索至少選修兩門課程的學生學號
SELECT student.S# ,
student.Sname
FROM student ,
SC
WHERE student.S# = SC.S#
GROUP BY student.S# ,
student.Sname
HAVING COUNT(1) >= 2
ORDER BY student.S#
--45、查詢選修了全部課程的學生信息
--方法1 根據數量來完成
SELECT student.*
FROM student
WHERE S# IN ( SELECT S#
FROM sc
GROUP BY S#
HAVING COUNT(1) = ( SELECT COUNT(1)
FROM course
) )
--方法2 使用雙重否定來完成
SELECT t.*
FROM student t
WHERE t.S# NOT IN ( SELECT DISTINCT
m.S#
FROM ( SELECT S# ,
C#
FROM student ,
course
) m
WHERE NOT EXISTS ( SELECT 1
FROM sc n
WHERE n.S# = m.S#
AND n.C# = m.C# ) )
--方法3 使用雙重否定來完成
SELECT t.*
FROM student t
WHERE NOT EXISTS ( SELECT 1
FROM ( SELECT DISTINCT
m.S#
FROM ( SELECT S# ,
C#
FROM student ,
course
) m
WHERE NOT EXISTS ( SELECT 1
FROM sc n
WHERE n.S# = m.S#
AND n.C# = m.C# )
) k
WHERE k.S# = t.S# )
--46、查詢各學生的年齡
--46.1 只按照年份來算
SELECT * ,
DATEDIFF(yy, sage, GETDATE()) [年齡]
FROM student
--46.2 按照出生日期來算，當前月日 < 出生年月的月日則，年齡減一
SELECT * ,
CASE WHEN RIGHT(CONVERT(VARCHAR(10), GETDATE(), 120), 5) < RIGHT(CONVERT(VARCHAR(10), sage, 120),
5)
THEN DATEDIFF(yy, sage, GETDATE()) - 1
ELSE DATEDIFF(yy, sage, GETDATE())
END [年齡]
FROM student
--47、查詢本周過生日的學生
SELECT *
FROM student
WHERE DATEDIFF(week,
DATENAME(yy, GETDATE()) + RIGHT(CONVERT(VARCHAR(10), sage, 120),
6), GETDATE()) = 0
--48、查詢下周過生日的學生
SELECT *
FROM student
WHERE DATEDIFF(week,
DATENAME(yy, GETDATE()) + RIGHT(CONVERT(VARCHAR(10), sage, 120),
6), GETDATE()) = -1
--49、查詢本月過生日的學生
SELECT *
FROM student
WHERE DATEDIFF(mm,
DATENAME(yy, GETDATE()) + RIGHT(CONVERT(VARCHAR(10), sage, 120),
6), GETDATE()) = 0
--50、查詢下月過生日的學生
SELECT *
FROM student
WHERE DATEDIFF(mm,
DATENAME(yy, GETDATE()) + RIGHT(CONVERT(VARCHAR(10), sage, 120),
6), GETDATE()) = -1
DROP TABLE Student,Course,Teacher,SC