diff --git a/advlabdb/models.py b/advlabdb/models.py
index ffbc72f..44341de 100644
--- a/advlabdb/models.py
+++ b/advlabdb/models.py
@@ -18,6 +18,13 @@ from advlabdb.exceptions import DataBaseException
 
 MIN_MARK = 0
 MAX_MARK = 15
+MIN_YEAR = 22
+MAX_YEAR = 99
+MIN_STUDENT_NUMBER = 0
+MIN_EXPERIMENT_NUMBER = 1
+MIN_GROUP_NUMBER = 1
+MIN_DURATION_IN_DAYS = 1
+MIN_PART_NUMBER = 1
 
 
 def roundHalfUpToInt(number):
@@ -26,7 +33,9 @@ def roundHalfUpToInt(number):
 
 class Student(db.Model):
     id = db.Column(db.Integer, primary_key=True)
-    student_number = db.Column(db.Integer, db.CheckConstraint("student_number > -1"), nullable=False, unique=True)
+    student_number = db.Column(
+        db.Integer, db.CheckConstraint(f"student_number >= {MIN_STUDENT_NUMBER}"), nullable=False, unique=True
+    )
     first_name = db.Column(db.String(100), nullable=False)
     last_name = db.Column(db.String(100), nullable=False)
     uni_email = db.Column(db.String(200), nullable=False, unique=True)
@@ -137,7 +146,7 @@ class PartStudent(db.Model):
 
 class Group(db.Model):
     id = db.Column(db.Integer, primary_key=True)
-    number = db.Column(db.Integer, db.CheckConstraint("number > 0"), nullable=False)
+    number = db.Column(db.Integer, db.CheckConstraint(f"number > {MIN_GROUP_NUMBER}"), nullable=False)
 
     semester_id = db.Column(db.Integer, db.ForeignKey("semester.id"), nullable=False)
     program_id = db.Column(db.Integer, db.ForeignKey("program.id"), nullable=False)
@@ -227,14 +236,16 @@ class GroupExperiment(db.Model):
 
 class Experiment(db.Model):
     id = db.Column(db.Integer, primary_key=True)
-    number = db.Column(db.Integer, db.CheckConstraint("number > 0"), nullable=False)
+    number = db.Column(db.Integer, db.CheckConstraint(f"number > {MIN_EXPERIMENT_NUMBER}"), nullable=False)
     title = db.Column(db.String(200), nullable=False)
     description = db.Column(db.Text, nullable=True)
     wiki_link = db.Column(db.String(300), nullable=True)
     building = db.Column(db.String(100), nullable=False)
     room = db.Column(db.String(100), nullable=False)
     responsibility = db.Column(db.String(200), nullable=True)
-    duration_in_days = db.Column(db.Integer, db.CheckConstraint("duration_in_days > 0"), nullable=False)
+    duration_in_days = db.Column(
+        db.Integer, db.CheckConstraint(f"duration_in_days >= {MIN_DURATION_IN_DAYS}"), nullable=False
+    )
     active = db.Column(db.Boolean, default=True, nullable=False)
 
     program_id = db.Column(db.Integer, db.ForeignKey("program.id"), nullable=False)
@@ -407,7 +418,7 @@ class Appointment(db.Model):
 
 class Part(db.Model):
     id = db.Column(db.Integer, primary_key=True)
-    number = db.Column(db.Integer, db.CheckConstraint("number > 0"), nullable=False)
+    number = db.Column(db.Integer, db.CheckConstraint(f"number > {MIN_PART_NUMBER}"), nullable=False)
 
     program_id = db.Column(db.Integer, db.ForeignKey("program.id"), nullable=False)
     semester_id = db.Column(db.Integer, db.ForeignKey("semester.id"), nullable=False)
@@ -426,7 +437,9 @@ class Part(db.Model):
 class Semester(db.Model):
     id = db.Column(db.Integer, primary_key=True)
     label = db.Column(db.String(10), nullable=False)
-    year = db.Column(db.Integer, db.CheckConstraint("year > 0"), db.CheckConstraint("year < 100"), nullable=False)
+    year = db.Column(
+        db.Integer, db.CheckConstraint(f"year >= {MIN_YEAR}"), db.CheckConstraint(f"year <= {MAX_YEAR}"), nullable=False
+    )
 
     parts = db.relationship("Part", backref="semester", lazy=True)
     semester_experiments = db.relationship("SemesterExperiment", backref="semester", lazy=True)