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Nulls, three-valued logic, and ambiguity in SQL

Claude Rubinson
2007 SIGMOD record  
Date's popular critique of SQL's three-valued logic [4, 3] purports to demonstrate that SQL queries can produce erroneous results when nulls are present in the database.  ...  Although his critique is flawed, I agree with Date's general conclusion: SQL's use of nulls and three-valued logic introduces a startling amount of complexity into seemingly straightforward queries.  ...  And since the presence of a single null value taints the entire database [6] , one must generally assume three-valued logic.  ... 
doi:10.1145/1361348.1361350 fatcat:aktjshd6x5gppguxxln4lhwsqe

Handling SQL Nulls with Two-Valued Logic [article]

Leonid Libkin, Liat Peterfreund
2022 arXiv   pre-print
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.  ...  We show that, contrary to the widely held view, SQL could have been designed based on the standard Boolean logic, without any loss of expressiveness and without giving up nulls.  ...  INTRODUCTION To process data with nulls, SQL uses a three-valued logic (3VL). This is one of the most often criticized aspects of the language, and one that is very confusing to programmers.  ... 
arXiv:2012.13198v2 fatcat:znjim6svefezban5swagb3gxsq

Null values in SQL

John Grant
2008 SIGMOD record  
The purpose of this article is to show that, contrary to Rubinson's claim, Date's critique of query evaluation in the presence of null values in SQL is completely justified.  ...  In a recent article in the ACM SIGMOD Record, [8], Rubinson states that "Date misinterprets the meaning of his example query" and "SQL returns the correct answer to the query posed".  ...  be one of the above 3 values.  ... 
doi:10.1145/1462571.1462575 fatcat:ob3qrr6isfbqnfh45pjgn4k3su

Some remarks on self-tuning logical database design

F. De Marchi, M.-S. Hacid, J.-M. Petit
2005 21st International Conference on Data Engineering Workshops (ICDEW'05)  
Moreover, the huge number of null values occurring in practice may incur a significant overhead on his daily work, either to optimize the memory layout or to maintain (or design new) SQL queries.  ...  with respect to SQL workloads and the data themselves.  ...  Through the notion of assistant 2 , one could envision the self-tuning of logical database design from both SQL workloads and the data themselves.  ... 
doi:10.1109/icde.2005.287 dblp:conf/icde/MarchiHP05 fatcat:6aupc5bpbjarlnlqhxirrhhyaa

Do We Need Many-valued Logics for Incomplete Information?

Marco Console, Paolo Guagliardo, Leonid Libkin
2019 Proceedings of the Twenty-Eighth International Joint Conference on Artificial Intelligence  
by null values is no more powerful than the usual two-valued logic with the standard Boolean interpretation of the connectives.  ...  We impose rationality conditions on the semantics of the connectives of the propositional logic, and prove that Kleene's logic is the maximal sublogic to which the standard optimization rules apply, thereby  ...  As one example, consider the version of FO that underlies SQL and is based on Kleene's logic.  ... 
doi:10.24963/ijcai.2019/851 dblp:conf/ijcai/ConsoleGL19 fatcat:ygefts4zznbabdxkd3knhpp4y4

A Study on Database Fuzzy Query Method in SQL

ZHANG Peng
2011 Procedia Engineering  
However, logical connection always or Zadeh Based on fuzzy logic, this paper introduces the fuzzy theory and the relationship of the weight to the extended fuzzy query.  ...  This kind of fuzzy inquires the solved here through the fuzzy theory and the function of the SQL combination, which will improve the fuzzy inquiry system, so that the query will be more effective.  ...  Conclusion Based on the fuzzy SQL inquires and the study of the fuzzy theory, the logic of fuzzy language zadeh conjunction quantified, not the traditional OR.  ... 
doi:10.1016/j.proeng.2011.11.2653 fatcat:2stutqapfjeqfje5aqr3ilyn6a

A formal semantics of SQL queries, its validation, and applications

Paolo Guagliardo, Leonid Libkin
2017 Proceedings of the VLDB Endowment  
One is the first formal proof of the equivalence of basic SQL and relational algebra that extends to bag semantics and nulls.  ...  The other application looks at the three-valued logic employed by SQL, which is universally assumed to be necessary to handle nulls.  ...  The authors would like to thank the anonymous referees for their comments. Work partially supported by EPSRC grants N023056 and M025268.  ... 
doi:10.14778/3151113.3151116 fatcat:kriv2vdpdffuheayjuvldzmx5e

Comprehending nulls [article]

James Cheney, Wilmer Ricciotti
2021 arXiv   pre-print
However, SQL's treatment of incomplete information, using nulls and three-valued logic, is not compatible with 'standard' NRC based on two-valued logic.  ...  Nulls are widely used in practice for incomplete data, but the question of how to accommodate SQL-style nulls and incomplete information in NRC, or integrate such queries into a typed programming language  ...  ACKNOWLEDGMENTS This work was supported by ERC Consolidator Grant Skye (grant number ERC 682315), and by an ISCF Metrology Fellowship grant provided by the UK government's Department for Business, Energy  ... 
arXiv:2107.11347v1 fatcat:6r6z3mru3nh6fet6lhjwf2k2zi

The problem of missing data in geoscience databases

Stephen Henley
2006 Computers & Geosciences  
One of the most serious problems with SQL is the way it handles missing data. It uses a special value 'NULL' to represent data items whose value is not known.  ...  Relational database theorists advocate that a strict two-valued logic (true/false) be used instead, with prohibition of the use of NULL, and justify this stance by assertion that it is a true representation  ...  Acknowledgements The author gratefully acknowledges useful discussions with and helpful suggestions by Professor George Bardossy, Dr. T. Victor Loudon, and Dr. Peter Robson.  ... 
doi:10.1016/j.cageo.2005.12.008 fatcat:3qrs37iqcbb5tcqt5l36gv6twu

Ultrawrap: SPARQL execution on relational data

Juan F. Sequeda, Daniel P. Miranker
2013 Journal of Web Semantics  
The experiment is embodied in a system, Ultrawrap, that encodes a logical representation of the database as an RDF graph using SQL views and a simple syntactic translation of SPARQL queries to SQL queries  ...  In contrast, related research is predicated on incorporating optimizing transforms as part of the SPARQL to SQL translation, and/or executing some of the query outside the underlying SQL environment.  ...  rewrite the plan into one more typical of a comparable SQL query.  ... 
doi:10.1016/j.websem.2013.08.002 fatcat:sk4kbrnggjd4vk4zndokldmqce

Ultrawrap: SPARQL Execution on Relational Data

Juan Sequeda, Daniel P. Miranker
2013 Social Science Research Network  
The experiment is embodied in a system, Ultrawrap, that encodes a logical representation of the database as an RDF graph using SQL views and a simple syntactic translation of SPARQL queries to SQL queries  ...  In contrast, related research is predicated on incorporating optimizing transforms as part of the SPARQL to SQL translation, and/or executing some of the query outside the underlying SQL environment.  ...  rewrite the plan into one more typical of a comparable SQL query.  ... 
doi:10.2139/ssrn.3199073 fatcat:tnsv3g2amfdhfdglt3mwdldzyy

Query Rewrite for XML in Oracle XML DB [chapter]

M KRISHNAPRASAD, Z LIU, A MANIKUTTY, J WARNER, V ARORA, S KOTSOVOLOS
2004 Proceedings 2004 VLDB Conference  
It has the capability to physically store XML documents by shredding them as relational or object relational data, and creating logical XML documents using SQL/XML publishing functions.  ...  This technique integrates querying XML using XPath embedded inside SQL operators and SQL/XML publishing functions with the object relational and relational algebra.  ...  Acknowledements We gratefully acknowledge the contributions of all the members of the Oracle XML DB development and product management teams.  ... 
doi:10.1016/b978-012088469-8/50098-x fatcat:xh2kzi2hvbh7xpk6azriktkcjm

The man who wasn't there: The problem of partially missing data

Stephen Henley
2005 Computers & Geosciences  
in the form of NULLs, and even these are not handled properly by the SQL language. r  ...  The emphasis of both the relational theorists (Codd, Date, and others) and the developers of database systems is on commercial applications where only rudimentary treatment of missing data is required,  ...  SQL provides a three-valued logic (3VL) solution with most logical operations involving nulls leading to a new logic value unknown.  ... 
doi:10.1016/j.cageo.2005.01.010 fatcat:7rf56k7sifft3nll4kosfc6ree

Query Rewrite for XML in Oracle XML DB [chapter]

Muralidhar Krishnaprasad, Zhen Hua Liu, Anand Manikutty, James W. Warner, Vikas Arora, Susan Kotsovolos
2004 Proceedings 2004 VLDB Conference  
It has the capability to physically store XML documents by shredding them as relational or object relational data, and creating logical XML documents using SQL/XML publishing functions.  ...  This technique integrates querying XML using XPath embedded inside SQL operators and SQL/XML publishing functions with the object relational and relational algebra.  ...  Acknowledements We gratefully acknowledge the contributions of all the members of the Oracle XML DB development and product management teams.  ... 
doi:10.1016/b978-012088469-8.50098-x dblp:conf/vldb/KrishnaprasadLMWAK04 fatcat:icxkgdbd35fcfglxrddah4f6ii

Achieving Data Privacy through Secrecy Views and Null-Based Virtual Updates

Leopoldo Bertossi, Lechen Li
2013 IEEE Transactions on Knowledge and Data Engineering  
The virtual updates are based on null values as used in the SQL standard. We provide the semantics of secrecy views, virtual updates, and secret answers to queries.  ...  The different instances resulting from the virtually updates are specified as the models of a logic program with stable model semantics, which becomes the basis for computation of the secret answers.  ...  Support from Georg Gottlob, Thomas Eiter and a Pauli Fellowship of the "Wolfgang Pauli Institute, Vienna" is highly appreciated.  ... 
doi:10.1109/tkde.2012.86 fatcat:fzxrqwny2bdrvjmipodq6o2fr4
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