diff --git a/uebungszettel_4.sql b/uebungszettel_4.sql
new file mode 100644
index 0000000..683f600
--- /dev/null
+++ b/uebungszettel_4.sql
@@ -0,0 +1,259 @@
+--4.1)
+--a)
+CREATE TABLE UEBUNG4 (
+    ID NUMBER,
+    NAME VARCHAR2(20)
+);
+--b)
+CREATE SEQUENCE UEBUNG4_SEQ
+START WITH 1
+INCREMENT BY 5;
+--c)
+DECLARE
+    v_name VARCHAR2(20);
+    v_id NUMBER;
+BEGIN
+    -- Insert the student with the most enrollments
+    INSERT INTO UEBUNG4 (ID, NAME)
+    SELECT UEBUNG4_SEQ.NEXTVAL, NAME
+    FROM students
+    WHERE enrollments = (SELECT MAX(enrollments) FROM students);
+    DBMS_OUTPUT.PUT_LINE('Inserted student with most enrollments');
+    SAVEPOINT A;
+
+    -- Insert the student with the fewest enrollments
+    INSERT INTO UEBUNG4 (ID, NAME)
+    SELECT UEBUNG4_SEQ.NEXTVAL, NAME
+    FROM students
+    WHERE enrollments = (SELECT MIN(enrollments) FROM students);
+    DBMS_OUTPUT.PUT_LINE('Inserted student with fewest enrollments');
+    SAVEPOINT B;
+
+    -- Insert the instructor with the most courses
+    INSERT INTO UEBUNG4 (ID, NAME)
+    SELECT UEBUNG4_SEQ.NEXTVAL, NAME
+    FROM instructors
+    WHERE courses = (SELECT MAX(courses) FROM instructors);
+    DBMS_OUTPUT.PUT_LINE('Inserted instructor with most courses');
+    SAVEPOINT C;
+
+    -- Store the ID of the inserted instructor
+    SELECT ID INTO v_id
+    FROM UEBUNG4
+    WHERE NAME = (SELECT NAME FROM instructors WHERE courses = (SELECT MAX(courses) FROM instructors));
+    DBMS_OUTPUT.PUT_LINE('Stored ID of instructor with most courses: ' || v_id);
+
+    -- Rollback the insertion of the instructor with the most courses
+    ROLLBACK TO SAVEPOINT C;
+    DBMS_OUTPUT.PUT_LINE('Rolled back insertion of instructor with most courses');
+
+    -- Insert the instructor with the fewest courses using v_id
+    INSERT INTO UEBUNG4 (ID, NAME)
+    SELECT v_id, NAME
+    FROM instructors
+    WHERE courses = (SELECT MIN(courses) FROM instructors);
+    DBMS_OUTPUT.PUT_LINE('Inserted instructor with fewest courses using stored ID');
+
+    -- Insert the instructor with the most courses using the sequence
+    INSERT INTO UEBUNG4 (ID, NAME)
+    SELECT UEBUNG4_SEQ.NEXTVAL, NAME
+    FROM instructors
+    WHERE courses = (SELECT MAX(courses) FROM instructors);
+    DBMS_OUTPUT.PUT_LINE('Inserted instructor with most courses using sequence ID');
+
+    COMMIT;
+END;
+/
+--4.2)
+DECLARE
+    v_date DATE := TO_DATE('&sv_user_date ' , 'DD-MM-YYYY' ) ;
+    v_day VARCHAR2( 15 ) ;
+BEGIN
+    v_day := RTRIM(TO_CHAR( v_date , 'DAY' ) ) ;
+    IF v_day IN ( 'SATURDAY' , 'SUNDAY') THEN
+    DBMS_OUTPUT. PUT_LINE ( v_date||' falls on weekend');
+    END IF;
+    --control resumes here
+    DBMS_OUTPUT. PUT_LINE ( 'Done . . . ' ) ;
+END;
+/
+-- For 14.10.2023
+DECLARE
+    v_date DATE := TO_DATE('14-10-2023', 'DD-MM-YYYY');
+    v_day VARCHAR2(15);
+BEGIN
+    v_day := RTRIM(TO_CHAR(v_date, 'DAY'));
+    IF v_day IN ('SATURDAY', 'SUNDAY') THEN
+        DBMS_OUTPUT.PUT_LINE(v_date || ' falls on weekend');
+    END IF;
+    DBMS_OUTPUT.PUT_LINE('Done...');
+END;
+/
+
+-- For 16.10.2023
+DECLARE
+    v_date DATE := TO_DATE('16-10-2023', 'DD-MM-YYYY');
+    v_day VARCHAR2(15);
+BEGIN
+    v_day := RTRIM(TO_CHAR(v_date, 'DAY'));
+    IF v_day IN ('SATURDAY', 'SUNDAY') THEN
+        DBMS_OUTPUT.PUT_LINE(v_date || ' falls on weekend');
+    END IF;
+    DBMS_OUTPUT.PUT_LINE('Done . . .');
+END;
+/
+--Remove RTRIM
+DECLARE
+    v_date DATE := TO_DATE('14-10-2023', 'DD-MM-YYYY');
+    v_day VARCHAR2(15);
+BEGIN
+    v_day := TO_CHAR(v_date, 'DAY');
+    DBMS_OUTPUT.PUT_LINE(v_day);
+    IF v_day IN ('SATURDAY', 'SUNDAY') THEN
+        DBMS_OUTPUT.PUT_LINE(v_date || ' falls on weekend');
+    END IF;
+    DBMS_OUTPUT.PUT_LINE('Done . . .');
+END;
+/
+--Rewrite using LIKE
+DECLARE
+    v_date DATE := TO_DATE('&sv_user_date', 'DD-MM-YYYY');
+    v_day VARCHAR2(15);
+BEGIN
+    v_day := RTRIM(TO_CHAR(v_date, 'DAY'));
+    DBMS_OUTPUT.PUT_LINE(v_day);
+    IF v_day LIKE 'SATURDAY%' OR v_day LIKE 'SUNDAY%' THEN
+        DBMS_OUTPUT.PUT_LINE(v_date || ' falls on weekend');
+    END IF;
+    DBMS_OUTPUT.PUT_LINE('Done . . .');
+END;
+/
+--Rewrite using if-else
+DECLARE
+    v_date DATE := TO_DATE('&sv_user_date', 'DD-MM-YYYY');
+    v_day VARCHAR2(15);
+BEGIN
+    v_day := RTRIM(TO_CHAR(v_date, 'DAY'));
+    IF v_day LIKE 'SATURDAY%' OR v_day LIKE 'SUNDAY%' THEN
+        DBMS_OUTPUT.PUT_LINE(v_date || ' falls on weekend');
+    ELSE
+        DBMS_OUTPUT.PUT_LINE(v_date || ' does not fall on weekend');
+    END IF;
+    DBMS_OUTPUT.PUT_LINE('Done . . .');
+END;
+/
+--rewrite using SYSDATE
+DECLARE
+    v_date DATE := SYSDATE;
+    v_day VARCHAR2(15);
+    v_time VARCHAR2(15);
+BEGIN
+    v_day := RTRIM(TO_CHAR(v_date, 'DAY'));
+    v_time := TO_CHAR(v_date, 'HH24:MI');
+    IF v_day LIKE 'SATURDAY%' OR v_day LIKE 'SUNDAY%' THEN
+        IF TO_NUMBER(TO_CHAR(v_date, 'HH24')) < 12 THEN
+            DBMS_OUTPUT.PUT_LINE(v_date || ' falls on weekend in the morning');
+        ELSE
+            DBMS_OUTPUT.PUT_LINE(v_date || ' falls on weekend in the afternoon');
+        END IF;
+    ELSE
+        DBMS_OUTPUT.PUT_LINE(v_date || ' does not fall on weekend');
+    END IF;
+    DBMS_OUTPUT.PUT_LINE('Done . . .');
+END;
+/
+--4.3)
+DECLARE
+    v_instructor_id NUMBER;
+    v_section_count NUMBER;
+BEGIN
+    -- Prompt the user to input the instructor ID
+    v_instructor_id := &instructor_id;
+
+    -- Query to count the number of sections taught by the instructor
+    SELECT COUNT(*)
+    INTO v_section_count
+    FROM sections
+    WHERE instructor_id = v_instructor_id;
+
+    -- Check if the number of sections is greater than 3
+    IF v_section_count > 3 THEN
+        DBMS_OUTPUT.PUT_LINE('Instructor ' || v_instructor_id || ' needs a vacation');
+    ELSE
+        DBMS_OUTPUT.PUT_LINE('Instructor ' || v_instructor_id || ' teaches ' || v_section_count || ' sections');
+    END IF;
+END;
+/
+--Aufgabe 4.4
+--Block 1
+DECLARE
+    v_num NUMBER;
+BEGIN
+    IF v_num > 0 THEN
+        DBMS_OUTPUT.PUT_LINE('v_num is greater than 0');
+    ELSE
+        DBMS_OUTPUT.PUT_LINE('v_num is not greater than 0');
+    END IF;
+END;
+/ 
+--Block 2
+DECLARE
+    v_num NUMBER;
+BEGIN
+    IF v_num > 0 THEN
+        DBMS_OUTPUT.PUT_LINE('v_num is greater than 0');
+    END IF;
+    IF NOT (v_num > 0) THEN
+        DBMS_OUTPUT.PUT_LINE('v_num is not greater than 0');
+    END IF;
+END;
+/
+
+--Aufgabe 4.5
+DECLARE
+    v_date DATE := SYSDATE;
+    v_day VARCHAR2(15);
+    v_time VARCHAR2(15);
+BEGIN
+    v_day := RTRIM(TO_CHAR(v_date, 'DAY'));
+    v_time := TO_CHAR(v_date, 'HH24:MI');
+
+    CASE 
+        WHEN v_day LIKE 'SATURDAY%' OR v_day LIKE 'SUNDAY%' THEN
+            CASE 
+                WHEN TO_NUMBER(TO_CHAR(v_date, 'HH24')) < 12 THEN
+                    DBMS_OUTPUT.PUT_LINE(v_date || ' falls on weekend in the morning');
+                ELSE
+                    DBMS_OUTPUT.PUT_LINE(v_date || ' falls on weekend in the afternoon');
+            END CASE;
+        ELSE
+            DBMS_OUTPUT.PUT_LINE(v_date || ' does not fall on weekend');
+    END CASE;
+
+    DBMS_OUTPUT.PUT_LINE('Done . . .');
+END;
+/
+
+--Aufgabe 4.6
+DECLARE
+    v_instructor_id NUMBER;
+    v_section_count NUMBER;
+BEGIN
+    -- Prompt the user to input the instructor ID
+    v_instructor_id := &instructor_id;
+
+    -- Query to count the number of sections taught by the instructor
+    SELECT COUNT(*)
+    INTO v_section_count
+    FROM sections
+    WHERE instructor_id = v_instructor_id;
+
+    -- Use a CASE statement to determine the output message
+    CASE 
+        WHEN v_section_count > 3 THEN
+            DBMS_OUTPUT.PUT_LINE('Instructor ' || v_instructor_id || ' needs a vacation');
+        ELSE
+            DBMS_OUTPUT.PUT_LINE('Instructor ' || v_instructor_id || ' teaches ' || v_section_count || ' sections');
+    END CASE;
+END;
+/
\ No newline at end of file