This comment on another thread links to a succinct presentation of the Relational Model which you might find helpful - https://news.ycombinator.com/item?id=3920

This comment on another thread links to a succinct presentation of the Relational Model which you might find helpful - https://news.ycombinator.com/item?id=39201972 https://news.ycombinator.com/item?id=39201972 Basically, SQL does not constrain one to a strict mathematical relational model since you can have ordering, duplicates, nulls etc.