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A Formalization of SQL with Nulls. [PDF]
J Autom Reason, 2022 AbstractSQL is the world’s most popular declarative language, forming the basis of the multi-billion-dollar database industry. Although SQL has been standardized, the full standard is based on ambiguous natural language rather than formal specification.
Ricciotti W, Cheney J.
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Relational Algebra and Calculus with SQL Null Values [PDF]
, 2022 The logic of nulls in databases has been subject of investigation since their introduction in Codd's Relational Model, which is the foundation of the SQL standard. We show a logical characterisation of a first-order fragment of SQL with null values, by first focussing on a simple extension with null values of standard relational algebra, which captures
Enrico Franconi, Sergio Tessaris
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SQL Nulls and Two-Valued Logic
Proceedings of the 42nd ACM SIGMOD-SIGACT-SIGAI Symposium on Principles of Database Systems, 2023 The design of SQL is based on a three-valued logic (3VL), rather than the familiar two-valued Boolean logic (2VL). In addition to true and false, 3VL adds unknown to handle nulls. Viewed as indispensable for SQL expressiveness, it is often criticized for unintuitive behavior of queries and for being a source of programmer mistakes.
Leonid Libkin, Liat Peterfreund
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Correctness of SQL Queries on Databases with Nulls [PDF]
ACM SIGMOD Record, 2017 Multiple issues with SQL's handling of nulls have been well documented. Having efficiency as its main goal, SQL disregards the standard notion of correctness on incomplete databases -- certain answers -- due to its high complexity. As a result, the evaluation of SQL queries on databases with nulls may produce answers that are just plain wrong. However,
Paolo Guagliardo, Leonid Libkin
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Handling SQL Nulls with Two-Valued Logic [PDF]
, 2020 The design of SQL is based on a three-valued logic (3VL), rather than the familiar Boolean logic. 3VL adds a truth value unknown to true and false to handle nulls. Viewed as indispensable for SQL expressiveness, it is at the same time much criticized for unintuitive behavior of queries and being a source of programmer mistakes.
Leonid Libkin, Liat Peterfreund
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On the Codd semantics of SQL nulls [PDF]
Information Systems, 2018 Abstract Theoretical models used in database research often have subtle differences with those occurring in practice. One particular mismatch that is usually neglected concerns the use of marked nulls to represent missing values in theoretical models of incompleteness, while in an SQL database these are all denoted by the same syntactic object ...
Paolo Guagliardo, Leonid Libkin
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Usability and optimization of online apps in user’s context [PDF]
PeerJ Computer ScienceThe OptiFlow framework introduces a novel approach for enhancing usability evaluation and optimization known as OptiFlow. This framework combines heuristic evaluation with a web-based platform to provide a comprehensive method for assessing and ...
M. Waseem Iqbal +5 more
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Research on Data Storage of Medical Record Based on Knowledge Graph [PDF]
Jisuanji gongcheng, 2019 Resource Description Framework(RDF) storage scheme based on relational database mostly does not consider the domain characteristics,resulting in insufficient query performance.Therefore,an improved medical record storage scheme is proposed.According to ...
XIA Yuhang,GAO Daqi,RUAN Tong,WANG Haofen,YIN Yichao
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MonetDB/XQuery: a fast XQuery processor powered by a relational engine [PDF]
, 2006 Relational XQuery systems try to re-use mature relational data management infrastructures to create fast and scalable XML database technology. This paper describes the main features, key contributions, and lessons learned while implementing such a system.
Boncz, P. +5 more
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Possible and certain SQL keys [PDF]
, 2015 Driven by the dominance of the relational model, the requirements of modern applications, and the veracity of data, we revisit the fundamental notion of a key in relational databases with NULLs. In SQL database systems primary key columns are NOT NULL by
Kohler, Henning +2 more
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