diff --git a/athena/athena/models/db_exercise.py b/athena/athena/models/db_exercise.py
index 13fd5593e..323cc5527 100644
--- a/athena/athena/models/db_exercise.py
+++ b/athena/athena/models/db_exercise.py
@@ -1,18 +1,27 @@
 from sqlalchemy import Column, String, Float, JSON, Enum as SqlEnum
-
+from sqlalchemy.orm import relationship
+from athena.database import Base
 from athena.schemas import ExerciseType
 from .model import Model
 from .big_integer_with_autoincrement import BigIntegerWithAutoincrement
 
 
-class DBExercise(Model):
+class DBExercise(Model, Base):
+    __tablename__ = "exercise"
     id = Column(BigIntegerWithAutoincrement, primary_key=True, index=True, nullable=False)
     lms_url = Column(String, index=True, nullable=False)
     title = Column(String, index=True, nullable=False)
-    type = Column(SqlEnum(ExerciseType), index=True, nullable=False)
     max_points = Column(Float, index=True, nullable=False)
     bonus_points = Column(Float, index=True, nullable=False)
     grading_instructions = Column(String)
     problem_statement = Column(String)
     grading_criteria = Column(JSON, nullable=True)
     meta = Column(JSON, nullable=False)
+
+    # Polymorphism, discriminator attribute
+    type = Column(SqlEnum(ExerciseType), index=True, nullable=False)
+
+    __mapper_args__ = {
+        'polymorphic_identity': 'exercise',
+        'polymorphic_on': 'type'
+    }
\ No newline at end of file
diff --git a/athena/athena/models/db_modeling_exercise.py b/athena/athena/models/db_modeling_exercise.py
index 450b32e77..818724ab8 100644
--- a/athena/athena/models/db_modeling_exercise.py
+++ b/athena/athena/models/db_modeling_exercise.py
@@ -1,14 +1,17 @@
-from sqlalchemy import Column, String
+from athena.schemas.exercise_type import ExerciseType
+from sqlalchemy import Column, String, ForeignKey
 from sqlalchemy.orm import relationship
-
-from athena.database import Base
 from .db_exercise import DBExercise
-
-
-class DBModelingExercise(DBExercise, Base):
+from .big_integer_with_autoincrement import BigIntegerWithAutoincrement
+class DBModelingExercise(DBExercise):
     __tablename__ = "modeling_exercises"
 
-    example_solution: str = Column(String)  # type: ignore
-
+    example_solution = Column(String)  # type: ignore
+    
+    id = Column(BigIntegerWithAutoincrement, ForeignKey('exercise.id'), primary_key=True)
     submissions = relationship("DBModelingSubmission", back_populates="exercise")
     feedbacks = relationship("DBModelingFeedback", back_populates="exercise")
+
+    __mapper_args__ = {
+        'polymorphic_identity': ExerciseType.modeling.value
+    }
\ No newline at end of file
diff --git a/athena/athena/models/db_programming_exercise.py b/athena/athena/models/db_programming_exercise.py
index b558dd58f..3060e5831 100644
--- a/athena/athena/models/db_programming_exercise.py
+++ b/athena/athena/models/db_programming_exercise.py
@@ -1,13 +1,15 @@
-from sqlalchemy import Column, String
+from athena.schemas.exercise_type import ExerciseType
+from sqlalchemy import Column, String, ForeignKey
 from sqlalchemy.orm import relationship
 
-from athena.database import Base
 from .db_exercise import DBExercise
+from .big_integer_with_autoincrement import BigIntegerWithAutoincrement
 
 
-class DBProgrammingExercise(DBExercise, Base):
+class DBProgrammingExercise(DBExercise):
     __tablename__ = "programming_exercises"
 
+    id = Column(BigIntegerWithAutoincrement, ForeignKey('exercise.id'), primary_key=True)
     programming_language: str = Column(String, nullable=False)  # type: ignore
     solution_repository_uri: str = Column(String, nullable=False) # type: ignore
     template_repository_uri: str = Column(String, nullable=False) # type: ignore
@@ -15,3 +17,7 @@ class DBProgrammingExercise(DBExercise, Base):
 
     submissions = relationship("DBProgrammingSubmission", back_populates="exercise")
     feedbacks = relationship("DBProgrammingFeedback", back_populates="exercise")
+
+    __mapper_args__ = {
+        'polymorphic_identity': ExerciseType.programming.value
+    }
\ No newline at end of file
diff --git a/athena/athena/models/db_text_exercise.py b/athena/athena/models/db_text_exercise.py
index f3c2823ef..05df9e5c0 100644
--- a/athena/athena/models/db_text_exercise.py
+++ b/athena/athena/models/db_text_exercise.py
@@ -1,14 +1,20 @@
-from sqlalchemy import Column, String
+from athena.schemas.exercise_type import ExerciseType
+from sqlalchemy import Column, String, ForeignKey
 from sqlalchemy.orm import relationship
 
-from athena.database import Base
 from .db_exercise import DBExercise
+from .big_integer_with_autoincrement import BigIntegerWithAutoincrement
 
 
-class DBTextExercise(DBExercise, Base):
+class DBTextExercise(DBExercise):
     __tablename__ = "text_exercises"
+    id = Column(BigIntegerWithAutoincrement, ForeignKey('exercise.id'), primary_key=True)
 
     example_solution: str = Column(String)  # type: ignore
 
     submissions = relationship("DBTextSubmission", back_populates="exercise")
     feedbacks = relationship("DBTextFeedback", back_populates="exercise")
+
+    __mapper_args__ = {
+        'polymorphic_identity': ExerciseType.text.value
+    }
\ No newline at end of file
diff --git a/athena/athena/schemas/grading_criterion.py b/athena/athena/schemas/grading_criterion.py
index 15225a7dc..f13e23768 100644
--- a/athena/athena/schemas/grading_criterion.py
+++ b/athena/athena/schemas/grading_criterion.py
@@ -26,4 +26,4 @@ class GradingCriterion(Schema, ABC):
                      {"credits": 0.0, "gradingScale": "Bad", "instructionDescription": "Some instructions", "feedback": "Try again!", "usageCount": 0}])
 
 class StructuredGradingCriterion(BaseModel):
-    criteria: List[GradingCriterion]
\ No newline at end of file
+    criteria: List[GradingCriterion]