Initial commit

Homework/Homework250515/Homework250515.sql

@@ -0,0 +1,63 @@
+-- 1. 统计离散数学的成绩分布情况，即按照各分数段统计人数
+CREATE PROCEDURE sp_GetDiscreteMathGradeDistribution
+AS
+BEGIN
+    DECLARE @CourseName NVARCHAR(20) = N'离散数学';
+    DECLARE @TargetCno CHAR(8);
+    SELECT @TargetCno = Cno
+    FROM Course
+    WHERE Cname = @CourseName;
+    SELECT GradeCategory AS N'成绩段',
+           COUNT(*)      AS N'人数'
+    FROM (SELECT CASE
+                     WHEN Grade >= 90 AND Grade <= 100 THEN N'90-100 (优秀)'
+                     WHEN Grade >= 80 AND Grade < 90 THEN N'80-89 (良好)'
+                     WHEN Grade >= 70 AND Grade < 80 THEN N'70-79 (中等)'
+                     WHEN Grade >= 60 AND Grade < 70 THEN N'60-69 (及格)'
+                     WHEN Grade >= 0 AND Grade < 60 THEN N'<60 (不及格)'
+                     END AS GradeCategory
+          FROM SC
+          WHERE Cno = @TargetCno) AS GradeDistribution
+    GROUP BY GradeCategory
+    ORDER BY CASE GradeCategory
+                 WHEN N'90-100 (优秀)' THEN 1
+                 WHEN N'80-89 (良好)' THEN 2
+                 WHEN N'70-79 (中等)' THEN 3
+                 WHEN N'60-69 (及格)' THEN 4
+                 WHEN N'<60 (不及格)' THEN 5
+                 END;
+END;
+Go
+
+-- 2. 统计任意一门课的平均成绩
+CREATE FUNCTION fn_GetAverageCourseGrade(@InputCno CHAR(8))
+    RETURNS DECIMAL(5, 2)
+AS
+BEGIN
+    DECLARE @AverageGrade DECIMAL(5, 2);
+    SELECT @AverageGrade = AVG(CAST(Grade AS DECIMAL(5, 2)))
+    FROM SC
+    WHERE Cno = @InputCno
+      AND Grade IS NOT NULL;
+    RETURN @AverageGrade;
+END;
+Go
+
+-- 3. 将学生选课成绩从百分制改为等级制（即A、B、C、D、E）
+CREATE PROCEDURE sp_UpdateSCGradeToClass
+AS
+BEGIN
+    BEGIN TRANSACTION;
+    UPDATE SC
+    SET Class =
+            CASE
+                WHEN Grade >= 90 AND Grade <= 100 THEN 'A'
+                WHEN Grade >= 80 AND Grade < 90 THEN 'B'
+                WHEN Grade >= 70 AND Grade < 80 THEN 'C'
+                WHEN Grade >= 60 AND Grade < 70 THEN 'D'
+                WHEN Grade >= 0 AND Grade < 60 THEN 'E'
+                END
+    WHERE Grade IS NOT NULL;
+    COMMIT TRANSACTION;
+END;
+Go