diff --git a/VinhTX_DB.sql b/VinhTX_DB.sql
new file mode 100644
index 0000000..1846deb
--- /dev/null
+++ b/VinhTX_DB.sql
@@ -0,0 +1,99 @@
+#create professor
+create table testdb.professor (
+	prof_id int primary key,
+    prof_lname varchar(50),
+    prof_fname varchar(50)
+);
+
+# create course
+create table testdb.course(
+	course_id int primary key,
+    course_name varchar(255)
+);
+
+# create room
+create table testdb.room (
+	room_id int primary key,
+    room_loc varchar(50),
+    room_cap varchar(50),
+    class_id int
+);
+
+# create class 
+create table testdb.class (
+	class_id int primary key,
+    class_name varchar(255),
+    prof_id int,
+    course_id int,
+    room_id int,
+    foreign key (prof_id) references professor(prof_id),
+    foreign key (course_id) references course(course_id)
+);
+
+# add foreign key for room table
+alter table testdb.room add foreign key (class_id) references class(class_id)
+
+# create student
+create table testdb.student (
+	stud_id int primary key,
+    stud_fname varchar(50),
+    stud_lname varchar(50),
+    stud_street varchar(255),
+    stud_city varchar(50),
+    stud_zip varchar(10)
+ )
+ 
+ # create enroll
+create table testdb.enroll (
+	stud_id int,
+    class_id int,
+    grade varchar(3),
+    primary key (stud_id, class_id),
+    foreign key (stud_id) references student(stud_id),
+    foreign key (class_id) references class(class_id)
+ )
+ 
+# những cặp student-professor có dạy học nhau và số lớp mà họ có liên quan
+ select stud_id, prof_id, count(class_id) num_class from (
+ select a.stud_id, b.prof_id, c.class_id from testdb.student a, testdb.professor b, testdb.class c, testdb.enroll d
+ where b.prof_id = c.prof_id and a.stud_id = d.stud_id and c.class_id = d.class_id) a group by stud_id, prof_id;
+ 
+# những course (distinct) mà 1 professor cụ thể đang dạy
+ select distinct prof_id, course_id from testdb.class;
+ 
+# những course (distinct) mà 1 student cụ thể đang học
+select distinct b.stud_id, a.course_id from tesdb.class a, testdb.enroll b where a.stud_id = b.stud_id;
+
+# điểm số trung bình của 1 học sinh cụ thể (quy ra lại theo chữ cái, và xếp loại học lực (weak nếu avg < 5, average nếu >=5 < 8, good nếu >=8 )
+select stud_id, case
+  when grade >= 0 and grade <= 2 then 'F'
+     when grade > 2 and grade <= 4 then 'D'
+     when grade > 4 and grade <= 6 then 'C'
+     when grade > 6 and grade <= 8 then 'B'
+     else 'A'
+ end grade_letter, case
+  when grade < 5 then 'weak'
+     when grade >=5 and grade < 8 then 'average'
+     else 'good' 
+ end level from (
+ select stud_id, avg(grade) grade from testdb.enroll group by stud_id) a;
+ 
+# điểm số trung bình của các class (quy ra lại theo chữ cái)
+select class_id, case
+  when grade >= 0 and grade <= 2 then 'F'
+     when grade > 2 and grade <= 4 then 'D'
+     when grade > 4 and grade <= 6 then 'C'
+     when grade > 6 and grade <= 8 then 'B'
+     else 'A'
+ end grade_letter from (
+ select class_id, avg(grade) grade from testdb.enroll group by class_id) a;
+ 
+# điểm số trung bình của các course (quy ra lại theo chữ cái)
+select course_id, case
+  when grade >= 0 and grade <= 2 then 'F'
+     when grade > 2 and grade <= 4 then 'D'
+     when grade > 4 and grade <= 6 then 'C'
+     when grade > 6 and grade <= 8 then 'B'
+     else 'A'
+ end grade_letter from (
+ select a.course_id, avg(b.grade) grade from testdb.class a, testdb.enroll b where a.class_id = b.class_id group by a.course_id) c
\ No newline at end of file