08_Clarisha Riezky Amalia_4-44_Mindmap Pertemuan 4.
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What Is a Database
A set interrelated, centrally coordinate data files that are stored with as litle data redundancy
A database consolidates records previously stored in separate files into a common pool and serves a variety of users and data processing applications
Advantage of Database
Data is integrated
Minimize data redundancy and inconsistencies
Data is independent of the programs that use the data
Data is easily accessed for reporting and cross-functional analysis
DATABASE USER AND DESIGNERS
Different users of the database information are at an external level of the database. These users have logical views of the data.
Designers of a database need to understand user’s needs and the conceptual level of the entire database as well as the physical view.
A schema is a description of the data elements in a database, the relationships among them, and the logical model used to organize and describe the data
The conceptual-level schema
the organization-wide view of the entire database, lists all data elements and the relationships among them.
The external-level schema
an individual user’s view of portions of a database
The internal-level schema
a low-level view of the database, describes how the data are stored and accessed, including record layouts, definitions, addresses, and indexes.
To design a database, you need to have a conceptual view of the entire database. The conceptual view illustrates the different files and relationships between the files
Data Definition Language (DDL)
Builds the data dictionary
Creates the database
Describes logical views for each user
Specifies record or field security constraints
Data Manipulation Language (DML)
Changes the content in the database
Data Query Language (DQL)
Enables users to retrieve, sort, and display specific data from the database
Represents the conceptual and external schema as if that “data view” were truly stored in one table
Each row called a tuple, contains data about a specific item in a database table. This is equivalent to a record
Each column contains data about an attribute of of an entity. This is equivalent to a field
Users may want specific information found in a relational database and not have to sort through all the files to get that information. So they query (ask a question) the data.
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