Correctness of SQL Queries on Databases with Nulls

被引：11
作者：
Guagliardo, Paolo [1 ]
Libkin, Leonid [1 ]
机构：
[1] Univ Edinburgh, Sch Informat, Edinburgh, Midlothian, Scotland
来源：
SIGMOD RECORD | 2017年 / 46卷 / 03期
基金：
英国工程与自然科学研究理事会;
关键词：
Algebra;
D O I：
10.1145/3156655.3156657
中图分类号：
TP [自动化技术、计算机技术];
学科分类号：
0812 ;
摘要：
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, SQL evaluation can be modified, at least for relational algebra queries, to approximate certain answers, i.e., return only correct answers. We examine recently proposed approximation schemes for certain answers and analyze their complexity, both theoretical bounds and real-life behavior.
引用
收藏
页码：5 / 16
页数：12
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