Editing Relational model (section)

=== SQL and the relational model ===
SQL, initially pushed as the [[standardization|standard]] language for [[relational database]]s, deviates from the relational model in several places. The current [[International Organization for Standardization|ISO]] SQL standard doesn't mention the relational model or use relational terms or concepts.{{citation needed|date=December 2023}}

According to the relational model, a Relation's attributes and tuples are [[Set (mathematics)|mathematical sets]], meaning they are unordered and unique. In a SQL table, neither rows nor columns are proper sets. A table may contain both duplicate rows and duplicate columns, and a table's columns are explicitly ordered. SQL uses a [[Null (SQL)|Null]] value to indicate missing data, which has no analog in the relational model. Because a row can represent unknown information, SQL does not adhere to the relational model's ''Information Principle''.<ref name="professionals">{{cite book |last1=Date |first1=Chris J. |title=Relational Theory for Computer Professionals: What Relational Databases are Really All About |date=2013 |publisher=O'Reilly Media |location=Sebastopol, Calif |isbn=978-1-449-36943-9 |edition=1.}}</ref>{{rp|153–155,162}}