Database Management Systems: Chapter 3 - Algorithms for Query Processing and Optimization Introduction to Query Processing; Translating SQL Queries into Relational Algebra; Algorithms for External Sorting; Algorithms for SELECT and JOIN Operations;...
The Oracle database engine has become a huge piece of software. This not only means that a single human can no longer be roficient in using all the features provided in recent versions, but it also means that some of them will rarely be used. Actually, in most situations, it is enough to know and take advantage of a limited number of core features in order to use the Oracle database
engine efficiently and successfully.
Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí y học Molecular Biology cung cấp cho các bạn kiến thức về ngành sinh học đề tài: On the optimality of the neighbor-joining algorithm...
The degree that any activity is aesthetic and educative—whether lifting
a stone, creating art, or solving scientific problems—is related to the
degree that active doing and receptive undergoing are joined in percep-
tion. We do something, we undergo its consequences, we do something
in response, we undergo again. And so on. The experience becomes
educative as we grasp the relationship between doing and undergoing.
The experience is transformative as we have new thoughts, feelings, and
action, and also as the world reveals itself and acts...
Early relational systems used indices as table replicas that allowed
vertical partitioning, allowed associative search, and allowed con-
venient data ordering. Database optimizers and executors use
semi-join on these structures to run common queries on covering
indices. These query strategies give huge speedups.
These early ideas evolved to materialized views (often maintained
by triggers) that went far beyond simple covering indices and
provided fast access to star and snowflake schema. In...
For small join tables, REED always chooses to push
them into the network if their selectivity is smaller than
one. For intermediate tables, the REED query optimizer
makes a decision as to whether to push the join into the
network based on the estimated selectivity of the predicate
(which may be learned from past performance or gathered
statistics, or estimated using basic query optimization tech-
niques ) and the average depth of sensor nodes in the
In shared-nothing database systems, data often needs to be moved whenever there is a join or an aggregation process
for which the data requires repartitioning across the segments. As a result, the interconnect serves as one of the most
critical components within Greenplum Database. Greenplum’s gNet interconnect (Figure 8m) optimizes the flow of
data to allow continuous pipelining of processing without blocking on all nodes of the system.
Query processing in the original TinyDB implementation
works as follows. The query is input on the user’s PC, or
basestation. This query is optimized to improve execution;
currently, TinyDB only considers the order of selection
predicates during optimization (as the existing version does
not support joins). Once optimized, the query is translated
into a sensor-network specific format and injected into the
network via a gateway node.
The product type of the Target of Evaluation (TOE) described in this ST is a database
management system (DBMS) with the capability to limit TOE access to authorized users,
enforce Discretionary Access Controls on objects under the control of the database
management system based on user and/or role authorizations, and to provide user
accountability via audit of users‘ actions.
A DBMS is a computerized repository that stores information and allows authorized users to
retrieve and update that information.
Gamma uses traditional relational techniques for query parsing, optimization [SELI79, JARK84], and code
generation. The optimization process is somewhat simpliﬁed as Gamma only employs hash-based algorithms for
joins and other complex operations. Queries are compiled into a left-deep tree of operators. At execution time,
each operator is executed by one or more operator processes at each participating site.
now is the time for all partners to join forces in a
concerted effort. this means scaling up and prioritizing
a package of high-impact interventions, strengthening
health systems, and integrating efforts across diseases
and sectors such as health, education, water, sanitation
and nutrition. It also means promoting human rights,
gender equality and poverty reduction.
all actors should work to optimize current investments.