DATABASE SYSTEMS (phần 26) pot
Sổ tay phụ huynh - Phần 26 pot
... trẻ sử dụng một tay nào đó để làm mọi
việc. Có một số trẻ thuận cả hai tay cho đến 5-6 tuổi và sau đó tự chúng sẽ chọn
lựa chúng thích sử dụng tay nào hơn.
Số người thuận tay trái trên thế ... thuận tay nào bị
ảnh hưởng lớn bởi yếu tố di truyền. Nếu cả hai vợ chồng đều thuận tay trái thì đứa
trẻ có 42% khả năng cũng sẽ thuận tay trái. Và nếu bạn tò mò muốn biết trẻ thuận...
DATABASE SYSTEMS (phần 1) ppt
... using,
and
imple-
menting
database
systems
and
applications.
Our
presentations
stresses
the
fundamentals
of database
modeling
and
design,
the
languages
and
facilities
provided
by
the
database
management
systems,
and
system
implementation
techniques.
The
book
is
meant
to
be
used ... I
Chapter
1
Databases
and
Database
Users
DATABASE
SYSTEM
UserS/Programmers
~
Application Programs/...
DATABASE SYSTEMS (phần 2) doc
... databases
and
Web
pages.
XML
combines
concepts
from
the
models
used in
document
systems
with
database
modeling
concepts.
1.7.5
Extending
Database
Capabilities for
New
Applications
The
success of database systems in traditional applications ... processing
and
optimization,
their
performance
improved. Eventually,
relational
databases
became
the
dominant
type of
database
systems
fo...
DATABASE SYSTEMS (phần 4) pot
... concepts (see
Chapter
24).
• KR schemes include reasoning
mechanisms
that
deduce additional facts from the
facts stored in a database.
Hence,
whereas most
current
database systems are limited
to ... relational database
and
a rela-
tional database schema. A
relational
database
schema
S is a set of relation schemas S =
(R
I
,
R
z
,
, R
m
}
and
a set of
integrity
constraints
IC....
DATABASE SYSTEMS (phần 5) ppt
... as
RM/T.
Childs
(1968)
had
earlier used set theory to model databases. Later,
Codd (1990) published a
book
examining over
300
features of
the
relational
data
model
and database systems.
Since Codd's pioneering ... whose
DNUM
= 5. We
can
therefore write:
IF (x.DNUM =5)
THEN
F
z
which
is
equivalent
to
(NOT
(x.DNUM =5)
OR
F
z
)
3. Formula F
I
,
hence, is of
the
form NOT(x.DNuM =5)
OR...
DATABASE SYSTEMS (phần 6) docx
... success
of
rela-
tional
databases in
the
commercial world. Because it became a standard for relational
databases,
users were less
concerned
about
migrating
their
database applications from
other
types of database
systems- for
example,
network
or ... 10
b
5
FIGURE
6.13
A
database
state for
the
relations T1
and
T2.
Relational Database
Design by
ER-
and
EER-to-Relational
Mapping
We now...
DATABASE SYSTEMS (phần 7) pdf
... appropriate
SQL
DDL
statements
to define
the
database.
8.8.
Repeat Exercise 8.7,
but
use
the
AIRLINE database schema of Figure 5.8.
8.9.
Consider
the
LIBRARY
relational database
schema
of Figure 6.12.
Choose
the
appro-
priate
action
(reject, ... updating,
and
the
specification of views. Most database systems
have
an interactive
interface
where these SQL commands
can
be typed directl...
DATABASE SYSTEMS (phần 8) doc
... a
constraint
between
two sets of attributes from the
database.
Suppose
that
our
relational database schema has n attributes
AI'
A
2
,
•••
, An; let us
think
of
the
whole database as being described by a single
universal
relation ... {
6)
System.out.println
("Driver could not be loaded") ;
7) }
8)
String
dbacct, passwrd, ssn,
lname
9)
Double
salary
;
10) dbacct
= readent...
DATABASE SYSTEMS (phần 9) pps
... a relational database schema for this database application. First show all
the
functional dependencies
that
should hold among
the
attributes.
Then
design
relation schemas for
the
database
that
are
each
in ... becomes
questionable
when
the
constraints
on
which
they
are based are hard
to
understand or to
detect
by
the
database designers
and
users
who
must discover these constraints. Thu...
DATABASE SYSTEMS (phần 11) pot
... discussing
the
role of information systems in organizations;
database systems are looked
upon
as a
part
of information systems in large-scale
applica-
tions. We discussed
how
databases fit
within
an information ... and 11)
discuss
high
level
transaction
design
and
joint
analysis of
data
and
functions. Shasha
(1992) is an
excellent
source on database tuning.
Information
about
some...
DATABASE SYSTEMS (phần 14) potx
... (see
Chapter
6).
Practical Database
Design and Tuning
In this chapter, we first discuss
the
issues
that
arise in physical database design in
Section
16.1.
Then, we discuss
how
to
improve database performance through database
tuning
in
Section ... undertaking
physical
database design, we must have a good idea of the intended use of the database by defining the
queries and transacti...
DATABASE SYSTEMS (phần 20) potx
... in a database.
Because
part
of
the
theoretical foundation for some deductive database systems is
mathematical
logic, such rules are often referred to as logic databases.
Other
types of
systems, ... in
the
application programs
that
access
the
database.
Section
24.3 will give a brief overview of spatial
and
multimedia databases. Spatial
databases provide
concepts
for databases
that
kee...
DATABASE SYSTEMS (phần 21) potx
... types of distributed database systems, including federated and
multidatabase systems
and
highlights
the
problems of heterogeneity and the needs of
autonomy in federated database systems, which will ... retrieve
the
employee
25.7
Distributed Databases in
Oracle
I831
Net8
Database
server
Database
server
Net8
(c:::>c:::>c:::>
=
EMPtable
t-
,
,
Sales
,
database
CONNECT T...
DATABASE SYSTEMS (phần 26) pot
... 262
sequence interaction, 263-264
database programming languages, 255
database schema, 27-28, 115
database servers, 36, 263
database state, 28
database systems
active, 19
active database technology, 3
characteristics,
8-11
deductive, ... data, 902
database administrators
(DBA),
12
interfaces for, 34
security and, 734
database applications, 49, 52-53, 255, 262
database desi...
Database Management systems phần 1 potx
... 308
11 .3 Minimizing I/O Cost versus Number of I/Os 309
11 .3 .1 Blocked I/O 310
11 .3.2 Double Buffering 311
11 .4 Using B+ Trees for Sorting 312
11 .4 .1 Clustered Index 312
11 .4.2 Unclustered Index 313
11 .5 ... Replication 611
21. 8 Distributed Catalog Management 611
21. 8 .1 Naming Objects 612
21. 8.2 Catalog Structure 612
21. 8.3 Distributed Data Independence 613
2...