[4sem] add db course files

4sem/db/lab11.sql

@@ -0,0 +1,21 @@
+DROP FUNCTION IF EXISTS dbo.AverageMark;
+DROP FUNCTION IF EXISTS dbo.CreditsList;
+GO;
+
+CREATE FUNCTION dbo.AverageMark(@disciplineId int) RETURNS float AS BEGIN;
+    DECLARE @out float = (SELECT AVG(CAST(Оценка AS FLOAT)) FROM Изучение WHERE Дисциплина = @disciplineId);
+    RETURN IIF(@out < 2, ROUND(@out, 0), @out);
+END;
+GO;
+
+CREATE FUNCTION dbo.CreditsList(@groupId int, @semester int) RETURNS table AS RETURN (
+    SELECT DISTINCT D.[Название], D.[Отчётность] FROM [Дисциплина] AS D
+    JOIN [Группа] as G on G.ID = @groupId
+    WHERE D.[Семестр] = @semester AND G.[КодСпециальности] = D.[КодСпециальности]
+);
+GO;
+
+SELECT dbo.AverageMark(4), dbo.AverageMark(12), dbo.AverageMark(2);
+SELECT * FROM dbo.CreditsList(2, 2);
+SELECT * FROM dbo.CreditsList(4,1);
+