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Results tagged with db.databases
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user 109
Questions in database theory
4
votes
What are recent advances in relational databases?
The biggest "advance" in relational databases has been the cleaving apart of the monolithic RDBMS model into discrete components, that are then put together in novel ways. These include data stores t …
- 19.2k
5
votes
Accepted
How do you argue a query is impossible in a query language like SPARQL or SQL?
From page 52 of Leonid Libkin's Elements of Finite Model Theory textbook:
Since we know that graph connectivity is not Hanf-local and transitive closure is not Gaifman-local, we immediately obtain …
- 19.2k
10
votes
Accepted
DATALOG references
Most of what you are looking for is well-covered in the survey
Stefano Ceri, Georg Gottlob, and Letizia Tanca, What you always wanted to know about Datalog (and never dared to ask), IEEE Transaction …
- 19.2k
16
votes
Why do relational databases work at all, given the theoretical exponential complexity of ans...
There are large classes of queries which are "easy", even in the worst case. In particular, if the class of queries contains conjunctive queries only and each query has bounded width (for instance tr …
- 19.2k
6
votes
Minimize a datalog program
There does not seem to be a general algorithm.
Checking whether two Datalog programs are equivalent (in the sense of producing the same output database for every possible input database) is undecidab …
- 19.2k
14
votes
Accepted
How do database aggregations form a monoid?
You ask why database aggregations have monoidal structure.
Say we want to combine data values $a$ and $b$, but want to keep things general -- these may be integers, strings, floating point numbers, v …
- 19.2k