app/models/student_batch.py

from sqlalchemy import Table, Column, String, ForeignKey, Index
from app.db.database import Base

# Pure association table — no ORM class needed
student_batch_table = Table(
    "student_batch",
    Base.metadata,
    Column("student_id", String(36), ForeignKey("students.id", ondelete="CASCADE"), primary_key=True),
    Column("batch_id",   String(36), ForeignKey("batches.id",  ondelete="CASCADE"), primary_key=True),
    Index("ix_student_batch_batch_id", "batch_id"),
)