100% tevredenheidsgarantie Direct beschikbaar na betaling Zowel online als in PDF Je zit nergens aan vast
logo-home
Summary Data wrangling and data analysis €5,99
In winkelwagen

Samenvatting

Summary Data wrangling and data analysis

 169 keer bekeken  14 keer verkocht

Applied Data Science Utrecht University (UU): Data handling and preparation, supervised & non-supervised machine learning, using SQL, Python, and R.

Voorbeeld 2 van de 102  pagina's

  • 18 november 2021
  • 102
  • 2021/2022
  • Samenvatting
Alle documenten voor dit vak (3)
avatar-seller
Samme
Silberschatz Et Al. 2019 – Database Systems Concepts
1.1. Database-System Applications
Database-management system (DBMS): collection of interrelated data and a set of
programs to access those data goal of a DBMS is information storage and manipulation

- Back-office: database internal of an organisation
- End-users: interaction between user and database within organisation

Two modes of databases usage:

- Online transaction processing: where large number users use the database, with
each user retrieving relatively small amounts of data, and performing small updates
- Data analytics: the processing of data to draw conclusions, and infer rules or decision
procedures, which are then used to drive business decisions

The field of data mining combines knowledge-discovery techniques invented by artificial
intelligence researchers and statistical analysts with efficient implementation techniques that
enable them to be used on extremely large databases

1.2. Purpose of Database Systems
File-processing system: store permanent records in various files, and it needs different
application programs to extract records from, and add records to, the appropriate files.
Disadvantages organizational information in file-processing system:

- Data redundancy and inconsistency: different programmers / structures /
programming languages or double data per identifier over different groups
o Redundancy leads to higher storage and costs
o Inconsistency leads to disagreement of data
- Difficulty in accessing data: conventional file-processing environments do not
allow needed data to be retrieved in a convenient and efficient manner. More
responsive data-retrieval systems are required for general use
- Data isolation: because data is scattered in various files, and files may be in different
formats, writing new application programs to retrieve the appropriate data is difficult
- Integrity problems: data values stored in the data base must satisfy certain types of
consistency constraints, because new data and software may be dissimilar
- Atomicity problems: a computer system is subject to failure; data transfer must be
atomic — it must happen in its entirety or not at all
- Concurrent access anomalies: systems must allow multiple users to update data
simultaneously. The system must maintain some form of supervision
- Security problems: not every user of the database system should be able to access
all the data


1

, 1.3. View of Data
The data models can be classified into four different categories:

- Relational model: collection of tables to represent both data and the relationships
among those data (record-based model; matrix / excel sheet)
- Entity-relationship (E-R) model: collection of basic objects, called entities, and
relationships among these objects
- Semi-structured data model: permit the specification of data where individual
data items of the same type may have different sets of attributes (JSON / XML)
- Object-based data model: database systems allow procedures to be stored in the
database system and executed by the database system (Java, C++, or C#)

Database-system users are not computer trained, developers hide the complexity from users
through several levels of data abstraction, to simplify users’ interactions with the system:

- Physical level: lowest level of abstraction describes how the data are stored. The
physical level describes complex low-level data structures in detail
- Logical level: next-higher level of abstraction describes what data are stored in the
database, and what relationships exist among those data. The logical level thus
describes the entire database in terms of a small number of relatively simple structures
- View level: highest level of abstraction describes only part of the entire database.
Even though the logical level uses simpler structures, complexity remains because of
the variety of information stored in a large database

Instance: collection of information stored in the database at a particular moment

Schema: overall design of the database (physical; logical schema; view level subschema)

1.4. Database Languages
Database systems provide a data-definition language (DDL) to specify database schema
and a data-manipulation language (DML) to express database queries and updates (SQL)

Database systems implement only integrity constraints testable with minimal overhead:

- Domain constraints: domain of possible values must be associated with every
attribute (for example, integer types, character types, date/time types)
- Referential integrity: ensure that a value that appears in one relation for a given set
of attributes also appears in a certain set of attributes in another relation
- Authorisation: differentiate among users as far as type of access they are permitted
on various data values in the database; read / insert / update / delete authorisation

Data-definition language: SQL provides a rich DDL that allows one to define tables with
data types and integrity constraints


2

Voordelen van het kopen van samenvattingen bij Stuvia op een rij:

Verzekerd van kwaliteit door reviews

Verzekerd van kwaliteit door reviews

Stuvia-klanten hebben meer dan 700.000 samenvattingen beoordeeld. Zo weet je zeker dat je de beste documenten koopt!

Snel en makkelijk kopen

Snel en makkelijk kopen

Je betaalt supersnel en eenmalig met iDeal, creditcard of Stuvia-tegoed voor de samenvatting. Zonder lidmaatschap.

Focus op de essentie

Focus op de essentie

Samenvattingen worden geschreven voor en door anderen. Daarom zijn de samenvattingen altijd betrouwbaar en actueel. Zo kom je snel tot de kern!

Veelgestelde vragen

Wat krijg ik als ik dit document koop?

Je krijgt een PDF, die direct beschikbaar is na je aankoop. Het gekochte document is altijd, overal en oneindig toegankelijk via je profiel.

Tevredenheidsgarantie: hoe werkt dat?

Onze tevredenheidsgarantie zorgt ervoor dat je altijd een studiedocument vindt dat goed bij je past. Je vult een formulier in en onze klantenservice regelt de rest.

Van wie koop ik deze samenvatting?

Stuvia is een marktplaats, je koop dit document dus niet van ons, maar van verkoper Samme. Stuvia faciliteert de betaling aan de verkoper.

Zit ik meteen vast aan een abonnement?

Nee, je koopt alleen deze samenvatting voor €5,99. Je zit daarna nergens aan vast.

Is Stuvia te vertrouwen?

4,6 sterren op Google & Trustpilot (+1000 reviews)

Afgelopen 30 dagen zijn er 52510 samenvattingen verkocht

Opgericht in 2010, al 14 jaar dé plek om samenvattingen te kopen

Start met verkopen
€5,99  14x  verkocht
  • (0)
In winkelwagen
Toegevoegd