Initial commit

Homework/Homework250417/Work1.sql

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+Use Homework250417
+Go
+CREATE TABLE Employee(
+    EmployeeID INT PRIMARY KEY,
+    Name NVARCHAR(20),
+    Age INT,
+    Salary INT,
+);
+Go
+/* 删除员工表信息时，如果员工个数<5，不允许删除员工信息，
+   记录下企图删除员工信息的行为 */
+CREATE TABLE DelEmployeeAttempt(
+    AttemptID INT PRIMARY KEY IDENTITY(1,1),
+    EmployeeID INT,
+    AttemptTime DATETIME DEFAULT GETDATE(),
+);
+Go
+CREATE TRIGGER trg_DelEmployee
+ON Employee
+INSTEAD OF DELETE
+AS
+BEGIN
+    DECLARE @EmployeeCount INT;
+    SELECT @EmployeeCount = COUNT(*) FROM Employee;
+    IF @EmployeeCount < 5
+    BEGIN
+        INSERT INTO DelEmployeeAttempt (EmployeeID)
+        SELECT EmployeeID FROM DELETED;
+        RAISERROR(N'少于5名员工，无法删除', 16, 1);
+    END
+    ELSE
+    BEGIN
+        DELETE FROM Employee WHERE EmployeeID IN (SELECT EmployeeID FROM DELETED);
+        PRINT(N'删除员工信息成功');
+    END
+END;
+Go

Homework/Homework250417/Work2.sql

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+USE Homework250417
+Go
+/* 某公司想举行一个小型的联谊会，关系Male记录注册的男宾信息，关系Female记录注册的女宾信息。
+   建立一个触发器，将来宾的人数现在在50人以内。 */
+CREATE TABLE Male(
+    ID INT PRIMARY KEY IDENTITY(1,1),
+    Name NVARCHAR(20) NOT NULL,
+);
+CREATE TABLE Female(
+    ID INT PRIMARY KEY IDENTITY(1,1),
+    Name NVARCHAR(20) NOT NULL,
+);
+Go
+CREATE TRIGGER trg_LimitGuestCount_Male
+ON Male
+INSTEAD OF INSERT
+AS
+BEGIN
+    DECLARE @MaleCount INT;
+    DECLARE @FemaleCount INT;
+    DECLARE @TotalCount INT;
+    SELECT @MaleCount = COUNT(*) FROM Male;
+    SELECT @FemaleCount = COUNT(*) FROM Female;
+    SET @TotalCount = @MaleCount + @FemaleCount;
+    IF @TotalCount >= 50
+        RAISERROR(N'宾客人数已满，无法添加更多男宾', 16, 1)
+    ELSE
+    BEGIN
+        INSERT INTO Male (Name)
+        SELECT Name FROM INSERTED;
+        PRINT(N'添加男宾信息成功');
+    END
+END;
+Go
+CREATE TRIGGER trg_LimitGuestCount_Female
+    ON Female
+    INSTEAD OF INSERT
+    AS
+    BEGIN
+        DECLARE @MaleCount INT;
+        DECLARE @FemaleCount INT;
+        DECLARE @TotalCount INT;
+        SELECT @MaleCount = COUNT(*) FROM Male;
+        SELECT @FemaleCount = COUNT(*) FROM Female;
+        SET @TotalCount = @MaleCount + @FemaleCount;
+        IF @TotalCount >= 50
+            RAISERROR(N'宾客人数已满，无法添加更多女宾', 16, 1)
+        ELSE
+        BEGIN
+            INSERT INTO Female (Name)
+            SELECT Name FROM INSERTED;
+            PRINT(N'添加女宾信息成功');
+        END
+    END;
+Go
+-- Test