Databases Demystified a self teaching guide phần 10 pps
Databases Demystified a self teaching guide phần 10 pps
... letter A in the acronym ACID stands for:
a. Automated
b. Abbreviated
c. Atomicity
d. Autonomous
e. Analog
82. Database locks:
a. Are implemented in exactly the same way by all major database vendors
b. ... 261
models, database, 2
modules, 55
MOLAP databases, 299–301
msdb database, 261
multidimensional OLAP databases, 299–301
multiple joins, 77–80
multivalued attributes, 150
N
namespace,...
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... that ends every SQL statement.
In Oracle, a transaction is automatically started for each database user session as soon
as the user connects to the database. At any time, the database user can ... table’s data.
The ALTER TABLE Statement
The ALTER TABLE statement may be used to change many aspects of the definition
of a database table. Again, there is a wide variation in implementation a...
Databases Demystified a self teaching guide phần 1 doc
... models, a brief his
-
tory of databases, and the rationale for focusing on the relational model.
Properties of a Database
A database is a collection of interrelated data items that are managed as a ... database can be defined as the file
that contains the data items. Oracle Corporation defines their database as a collec
-
tion of physical files that are managed by an instance of...
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... screen
Constraints
A constraint is a rule placed on a database object (typically a table or column) that
restricts the allowable data values for that database object in some way. These are
most important ... relational databases were built by both IBM and UC Berkeley.
e. Nearly all the commercial relational databases are descendents of either
System R or INGRES.
18. Currently avai...
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... row are called aggregate functions. The following table shows
aggregate functions that are commonly used in relational databases:
Function Name Description
AVG Calculates the average value for a ... one-to-many, one-to-one, or many-to-many
5. The Microsoft Access Show Table dialog box:
a. Lists all tables in the database and allows for the metadata about tables
to be added, changed, and...
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... redundant data in tables
•
Storing summarized data in tables
Note also that normalization is intended to remove anomalies from databases that
are used for online transaction-processing systems. Databases ... Databases that store historical
data used solely for analytical purposes are not as subject to insert, update, and de
-
lete anomalies. Chapter 12 contains more information on data...
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... profile
Composite Default screen
194
Databases Demystified
Demystified / Databases Demystified / Oppel/ 225364-9 / Chapter 7
The Data Flow Diagram
The data flow diagram (DFD) is the most data centric of all the ... normalization is
a. To eliminate redundant data
b. To remove certain anomalies from the relations
c. To provide a reason to denormalize the database
d. To optimize data-...
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... considered
a best practice because it can lead to a lack of data sharing. Moreover, placing
geographic or organizational unit names in table names plays havoc every
time the organization changes.
CHAPTER ... synchronizing data updates for
any redundantly stored data
•
More expensive than the centralized model
•
Lack of guidelines and best practices for how to partition data and
applicatio...
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... even to a different version of the same vendor’s database).
Connecting Databases to Java Applications
Java started as a proprietary programming language (originally named Oak) that was
developed ... that
binds the API to the particular database and platform, and a definition known as the
ODBC data source contains the information necessary for a particular application to
connect with...
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... contains more data than a data warehouse.
e. The project has a lower overall cost than a data warehouse project.
16. Building a data warehouse first, followed by data marts:
a. Will delay data mart ... screen
CHAPTER 12 Databases for Online Analytical Processing
301
Demystified / Databases Demystified / Oppel/ 225364-9 / Chapter 12
Data Marts
A data mart is a subset of a...