{"id":"https://openalex.org/W2066837227","doi":"https://doi.org/10.1016/0022-0000(84)90080-1","title":"Database relations with null values","display_name":"Database relations with null values","publication_year":1984,"publication_date":"1984-02-01","ids":{"openalex":"https://openalex.org/W2066837227","doi":"https://doi.org/10.1016/0022-0000(84)90080-1","mag":"2066837227"},"language":"en","primary_location":{"id":"doi:10.1016/0022-0000(84)90080-1","is_oa":false,"landing_page_url":"https://doi.org/10.1016/0022-0000(84)90080-1","pdf_url":null,"source":{"id":"https://openalex.org/S141020589","display_name":"Journal of Computer and System Sciences","issn_l":"0022-0000","issn":["0022-0000","1090-2724"],"is_oa":false,"is_in_doaj":false,"is_core":true,"host_organization":"https://openalex.org/P4310320990","host_organization_name":"Elsevier BV","host_organization_lineage":["https://openalex.org/P4310320990"],"host_organization_lineage_names":["Elsevier BV"],"type":"journal"},"license":null,"license_id":null,"version":"publishedVersion","is_accepted":true,"is_published":true,"raw_source_name":"Journal of Computer and System Sciences","raw_type":"journal-article"},"type":"article","indexed_in":["crossref"],"open_access":{"is_oa":false,"oa_status":"closed","oa_url":null,"any_repository_has_fulltext":false},"authorships":[{"author_position":"first","author":{"id":"https://openalex.org/A5113467760","display_name":"Carlo Zaniolo","orcid":null},"institutions":[],"countries":[],"is_corresponding":true,"raw_author_name":"Carlo Zaniolo","raw_affiliation_strings":["Bell Laboratories, Holmdel, New Jersey 07733, USA"],"affiliations":[{"raw_affiliation_string":"Bell Laboratories, Holmdel, New Jersey 07733, USA","institution_ids":[]}]}],"institutions":[],"countries_distinct_count":0,"institutions_distinct_count":1,"corresponding_author_ids":["https://openalex.org/A5113467760"],"corresponding_institution_ids":[],"apc_list":{"value":2520,"currency":"USD","value_usd":2520},"apc_paid":null,"fwci":5.6774,"has_fulltext":false,"cited_by_count":264,"citation_normalized_percentile":{"value":0.95274883,"is_in_top_1_percent":false,"is_in_top_10_percent":true},"cited_by_percentile_year":{"min":89,"max":100},"biblio":{"volume":"28","issue":"1","first_page":"142","last_page":"166"},"is_retracted":false,"is_paratext":false,"is_xpac":false,"primary_topic":{"id":"https://openalex.org/T10317","display_name":"Advanced Database Systems and Queries","score":0.9995999932289124,"subfield":{"id":"https://openalex.org/subfields/1705","display_name":"Computer Networks and Communications"},"field":{"id":"https://openalex.org/fields/17","display_name":"Computer Science"},"domain":{"id":"https://openalex.org/domains/3","display_name":"Physical Sciences"}},"topics":[{"id":"https://openalex.org/T10317","display_name":"Advanced Database Systems and Queries","score":0.9995999932289124,"subfield":{"id":"https://openalex.org/subfields/1705","display_name":"Computer Networks and Communications"},"field":{"id":"https://openalex.org/fields/17","display_name":"Computer Science"},"domain":{"id":"https://openalex.org/domains/3","display_name":"Physical Sciences"}},{"id":"https://openalex.org/T11106","display_name":"Data Management and Algorithms","score":0.9995999932289124,"subfield":{"id":"https://openalex.org/subfields/1711","display_name":"Signal Processing"},"field":{"id":"https://openalex.org/fields/17","display_name":"Computer Science"},"domain":{"id":"https://openalex.org/domains/3","display_name":"Physical Sciences"}},{"id":"https://openalex.org/T10215","display_name":"Semantic Web and Ontologies","score":0.9955000281333923,"subfield":{"id":"https://openalex.org/subfields/1702","display_name":"Artificial Intelligence"},"field":{"id":"https://openalex.org/fields/17","display_name":"Computer Science"},"domain":{"id":"https://openalex.org/domains/3","display_name":"Physical Sciences"}}],"keywords":[{"id":"https://openalex.org/keywords/soundness","display_name":"Soundness","score":0.8715763092041016},{"id":"https://openalex.org/keywords/null","display_name":"Null (SQL)","score":0.8059906959533691},{"id":"https://openalex.org/keywords/relational-database","display_name":"Relational database","score":0.6286445260047913},{"id":"https://openalex.org/keywords/set","display_name":"Set (abstract data type)","score":0.6189772486686707},{"id":"https://openalex.org/keywords/computer-science","display_name":"Computer science","score":0.5169864892959595},{"id":"https://openalex.org/keywords/interpretation","display_name":"Interpretation (philosophy)","score":0.47885796427726746},{"id":"https://openalex.org/keywords/theoretical-computer-science","display_name":"Theoretical computer science","score":0.475715696811676},{"id":"https://openalex.org/keywords/mathematics","display_name":"Mathematics","score":0.47208163142204285},{"id":"https://openalex.org/keywords/simple","display_name":"Simple (philosophy)","score":0.44804394245147705},{"id":"https://openalex.org/keywords/relational-algebra","display_name":"Relational algebra","score":0.44290661811828613},{"id":"https://openalex.org/keywords/relational-model","display_name":"Relational model","score":0.4227336347103119},{"id":"https://openalex.org/keywords/algebra-over-a-field","display_name":"Algebra over a field","score":0.37583446502685547},{"id":"https://openalex.org/keywords/database","display_name":"Database","score":0.36197179555892944},{"id":"https://openalex.org/keywords/programming-language","display_name":"Programming language","score":0.16996082663536072},{"id":"https://openalex.org/keywords/pure-mathematics","display_name":"Pure mathematics","score":0.13433951139450073}],"concepts":[{"id":"https://openalex.org/C39920170","wikidata":"https://www.wikidata.org/wiki/Q693083","display_name":"Soundness","level":2,"score":0.8715763092041016},{"id":"https://openalex.org/C203763787","wikidata":"https://www.wikidata.org/wiki/Q371029","display_name":"Null (SQL)","level":2,"score":0.8059906959533691},{"id":"https://openalex.org/C5655090","wikidata":"https://www.wikidata.org/wiki/Q192588","display_name":"Relational database","level":2,"score":0.6286445260047913},{"id":"https://openalex.org/C177264268","wikidata":"https://www.wikidata.org/wiki/Q1514741","display_name":"Set (abstract data type)","level":2,"score":0.6189772486686707},{"id":"https://openalex.org/C41008148","wikidata":"https://www.wikidata.org/wiki/Q21198","display_name":"Computer science","level":0,"score":0.5169864892959595},{"id":"https://openalex.org/C527412718","wikidata":"https://www.wikidata.org/wiki/Q855395","display_name":"Interpretation (philosophy)","level":2,"score":0.47885796427726746},{"id":"https://openalex.org/C80444323","wikidata":"https://www.wikidata.org/wiki/Q2878974","display_name":"Theoretical computer science","level":1,"score":0.475715696811676},{"id":"https://openalex.org/C33923547","wikidata":"https://www.wikidata.org/wiki/Q395","display_name":"Mathematics","level":0,"score":0.47208163142204285},{"id":"https://openalex.org/C2780586882","wikidata":"https://www.wikidata.org/wiki/Q7520643","display_name":"Simple (philosophy)","level":2,"score":0.44804394245147705},{"id":"https://openalex.org/C95916125","wikidata":"https://www.wikidata.org/wiki/Q840540","display_name":"Relational algebra","level":3,"score":0.44290661811828613},{"id":"https://openalex.org/C40207289","wikidata":"https://www.wikidata.org/wiki/Q755662","display_name":"Relational model","level":3,"score":0.4227336347103119},{"id":"https://openalex.org/C136119220","wikidata":"https://www.wikidata.org/wiki/Q1000660","display_name":"Algebra over a field","level":2,"score":0.37583446502685547},{"id":"https://openalex.org/C77088390","wikidata":"https://www.wikidata.org/wiki/Q8513","display_name":"Database","level":1,"score":0.36197179555892944},{"id":"https://openalex.org/C199360897","wikidata":"https://www.wikidata.org/wiki/Q9143","display_name":"Programming language","level":1,"score":0.16996082663536072},{"id":"https://openalex.org/C202444582","wikidata":"https://www.wikidata.org/wiki/Q837863","display_name":"Pure mathematics","level":1,"score":0.13433951139450073},{"id":"https://openalex.org/C111472728","wikidata":"https://www.wikidata.org/wiki/Q9471","display_name":"Epistemology","level":1,"score":0.0},{"id":"https://openalex.org/C138885662","wikidata":"https://www.wikidata.org/wiki/Q5891","display_name":"Philosophy","level":0,"score":0.0}],"mesh":[],"locations_count":2,"locations":[{"id":"doi:10.1016/0022-0000(84)90080-1","is_oa":false,"landing_page_url":"https://doi.org/10.1016/0022-0000(84)90080-1","pdf_url":null,"source":{"id":"https://openalex.org/S141020589","display_name":"Journal of Computer and System Sciences","issn_l":"0022-0000","issn":["0022-0000","1090-2724"],"is_oa":false,"is_in_doaj":false,"is_core":true,"host_organization":"https://openalex.org/P4310320990","host_organization_name":"Elsevier BV","host_organization_lineage":["https://openalex.org/P4310320990"],"host_organization_lineage_names":["Elsevier BV"],"type":"journal"},"license":null,"license_id":null,"version":"publishedVersion","is_accepted":true,"is_published":true,"raw_source_name":"Journal of Computer and System Sciences","raw_type":"journal-article"},{"id":"pmh:oai:CiteSeerX.psu:10.1.1.19.1226","is_oa":false,"landing_page_url":"http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.19.1226","pdf_url":null,"source":null,"license":null,"license_id":null,"version":"submittedVersion","is_accepted":false,"is_published":false,"raw_source_name":"http://www.cs.ucla.edu/%7Ezaniolo/papers/nullvalues.pdf","raw_type":"text"}],"best_oa_location":null,"sustainable_development_goals":[{"score":0.7900000214576721,"display_name":"Reduced inequalities","id":"https://metadata.un.org/sdg/10"}],"awards":[],"funders":[],"has_content":{"pdf":false,"grobid_xml":false},"content_urls":null,"referenced_works_count":32,"referenced_works":["https://openalex.org/W91443868","https://openalex.org/W101983502","https://openalex.org/W1486310914","https://openalex.org/W1492228160","https://openalex.org/W1495302482","https://openalex.org/W1496815773","https://openalex.org/W1968915456","https://openalex.org/W2003017562","https://openalex.org/W2010272308","https://openalex.org/W2011039300","https://openalex.org/W2021611189","https://openalex.org/W2034642607","https://openalex.org/W2039610696","https://openalex.org/W2057773300","https://openalex.org/W2103219113","https://openalex.org/W2103343882","https://openalex.org/W2116436709","https://openalex.org/W2122789628","https://openalex.org/W2133384222","https://openalex.org/W2337288897","https://openalex.org/W2489748212","https://openalex.org/W2788164529","https://openalex.org/W6603704065","https://openalex.org/W6604169916","https://openalex.org/W6629123387","https://openalex.org/W6629655320","https://openalex.org/W6631393269","https://openalex.org/W6642623622","https://openalex.org/W6655925563","https://openalex.org/W6675925439","https://openalex.org/W6683895068","https://openalex.org/W6703338257"],"related_works":["https://openalex.org/W1983413912","https://openalex.org/W2056177422","https://openalex.org/W2583932101","https://openalex.org/W2056093042","https://openalex.org/W1583538690","https://openalex.org/W2166509456","https://openalex.org/W1974358179","https://openalex.org/W2002489304","https://openalex.org/W1542080972","https://openalex.org/W2066837227"],"abstract_inverted_index":null,"counts_by_year":[{"year":2026,"cited_by_count":1},{"year":2025,"cited_by_count":2},{"year":2024,"cited_by_count":2},{"year":2023,"cited_by_count":8},{"year":2022,"cited_by_count":3},{"year":2021,"cited_by_count":5},{"year":2020,"cited_by_count":1},{"year":2019,"cited_by_count":5},{"year":2018,"cited_by_count":2},{"year":2017,"cited_by_count":5},{"year":2016,"cited_by_count":28},{"year":2015,"cited_by_count":6},{"year":2014,"cited_by_count":7},{"year":2013,"cited_by_count":7},{"year":2012,"cited_by_count":13}],"updated_date":"2026-04-05T17:49:38.594831","created_date":"2025-10-10T00:00:00"}