Podcast
Questions and Answers
DML is primarily used for creating database schema.
False
SQL is an example of a procedural language.
False
FORTRAN is a non-procedural language.
False
SQL is used to specify how to get the required data.
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Application programs access databases only through language extensions to allow embedded SQL.
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SQL is the most widely used procedural language.
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COBOL is an example of a non-procedural language.
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The SQL query 'select customer.customer-name from customer where customer.customer-id = ‘192-83-7465’' is used to find the balances of all accounts held by the customer with customer-id 192-83-7465.
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Language extensions are used to allow embedded Java.
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ODBC is an application program interface.
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Study Notes
Database Overview
- A database is a structured collection of data, e.g., a telephone directory.
- A database is a data-centered mirror of an organization's business processes, where the structure of data reflects organizational processes and the content of data reflects the organization's history.
Database Management System (DBMS)
- A DBMS is a general-purpose software system that facilitates defining, constructing, manipulating, and sharing databases among various users and applications.
- An application program accesses the database by sending queries or requests for data to the DBMS.
Database Applications
- Databases are used in various applications, including banking, airlines, universities, sales, manufacturing, and human resources.
- Databases touch all aspects of our lives.
Purpose of Database Systems
- Databases were initially built on top of file systems, but this approach had drawbacks, including data redundancy and inconsistency, difficulty in accessing data, data isolation, integrity problems, atomicity of updates, and concurrent access by multiple users.
- Database systems offer solutions to these problems.
Levels of Abstraction
- Database systems comprise complex data structures, and abstraction is used to hide irrelevant details from users.
- There are three levels of data abstraction: physical, logical, and view levels.
View of Data
- An architecture for a database system consists of entities, attributes, and relationships.
Entities, Attributes, and Relationships
- An entity represents a real-world object or concept, such as an employee or a project.
- An attribute represents a property of interest that further describes an entity, such as an employee's name or salary.
- A relationship among two or more entities represents an association among the entities.
Relational Databases
- A relational database supports storage of data as a set of inter-related tables.
- Each table stores data about a set of entities, and each table row is a record about one entity.
- Each record column is a field specifying an attribute of the entity.
- Each record has a field that acts as a unique identifier of an entity.
- Relationships among entities are specified by referring to this unique identifier from other tables.
DBMS Languages
- DBMS languages include Data Definition Language (DDL) and Data Manipulation Language (DML).
Data Definition Language (DDL)
- DDL is a specification notation for defining the database schema.
- DDL compiler generates a set of tables stored in a data dictionary, which contains metadata (i.e., data about data).
Data Manipulation Language (DML)
- DML is a language for accessing and manipulating the data organized by the appropriate data model.
- DML includes query languages, such as SQL.
SQL
- SQL is a widely used non-procedural language for accessing and manipulating data.
- SQL is used to specify what data is required without specifying how to get those data.
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Description
Assess your knowledge of database systems with this quiz from Seiyun University's College of Applied Science - CS department.
