Editing SQL (section)

==Criticisms==
===Design===
SQL deviates in several ways from its theoretical foundation, the relational model and its tuple calculus.  In that model, a table is a [[set (mathematics)|set]] of tuples, while in SQL, tables and query results are [[list (computing)|list]]s of rows; the same row may occur multiple times, and the order of rows can be employed in queries (e.g., in the LIMIT clause).
Critics argue that SQL should be replaced with a language that returns strictly to the original foundation: for example, see ''The Third Manifesto'' by Hugh Darwen and C.J. Date (2006, {{ISBN|0-321-39942-0}}).

===Orthogonality and completeness===
Early specifications did not support major features, such as primary keys. Result sets could not be named, and subqueries had not been defined. These were added in 1992.<ref name="Early History" />

The lack of [[sum type]]s has been described as a roadblock to full use of SQL's user-defined types. JSON support, for example, needed to be added by a new standard in 2016.<ref name="Brandon21">{{cite web |last1=Brandon |first1=Jamie |title=Against SQL |url=https://scattered-thoughts.net/writing/against-sql/ |access-date=2 August 2021 |language=en |date=July 2021}}</ref>

===Null===
The concept of [[Null (SQL)|Null]] is the subject of some [[Null (SQL)#Criticisms|debate]]. The Null marker indicates the absence of a value, and is distinct from a value of 0 for an integer column or an empty string for a text column. The concept of Nulls enforces the [[Null (SQL)#Comparisons with NULL and the three-valued logic (3VL)|3-valued-logic in SQL]], which is a concrete implementation of the general [[Three-valued logic|3-valued logic]].<ref name="Early History" />

===Duplicates===
Another popular criticism is that it allows duplicate rows, making integration with languages such as [[Python (programming language)|Python]], whose data types might make accurately representing the data difficult,<ref name="Early History" /> in terms of parsing and by the absence of modularity. This is usually avoided by declaring a primary key, or a unique constraint, with one or more columns that uniquely identify a row in the table.

===Impedance mismatch===
In a sense similar to [[object–relational impedance mismatch]], a mismatch occurs between the declarative SQL language and the procedural languages in which SQL is typically embedded.{{Citation needed|date=February 2024}}