Difference b/w one first and one_none: first(): we create a table of student and insert data, after that we read from table with the query (# result = session.exec(select(Book).where(Book.name==book_name)).first()) for example different student have sama name so this query will be select the name which come in first:if there is no matching then it will be return none:
one(): result = session.exec(select(Book).where(Book.name==book_name)).one() this query will be match only with one row over all the table if they find out multiple row with the same name it will be return error: and if the not found any row they also return error:
one_none(): result = session.exec(select(Book).where(Book.id==book_id)).one_or_none() this will be perfect one b/z this query will be match with one row in over all the table if the find out it will be return the result otherwise it will be go the else: part