Introduction to Databases

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Questions and Answers

What is the primary purpose of using foreign keys in relational databases?

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How does maintaining data integrity through relationships in relational databases benefit data analysis?

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Which statement correctly defines primary keys in relational databases?

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What advantage does reducing data redundancy provide in relational databases?

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Why is entity identification important in relational databases?

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What is the purpose of the LIKE operator in SQL?

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How is the TRIM function used in SQL?

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In SQL, which operation would you use to return the first three characters of a string?

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Which logical operator would you use to negate a condition in SQL?

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What character does the wildcard '%' represent in SQL pattern matching?

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What type of operation do subqueries perform in SQL?

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Which SQL function would you use to find the total number of characters in a string?

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What does the UPPER function do in SQL?

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What does the SQL query 'SELECT carid, daily_rate, dailyrate - 5 AS discounted_rate FROM cars;' accomplish?

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Which SQL command is used to add a new column to an existing table?

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What is the result of performing a LEFT JOIN between two tables?

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Which SQL clause would you use to filter results after performing a JOIN?

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What does the following query do: SELECT COUNT(*) FROM table_name;?

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In the context of SQL, what does an INNER JOIN accomplish?

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Which statement is true regarding the syntax of the DELETE query?

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What is the purpose of using the SUM() function in SQL?

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Which SQL command is executed to remove a table from a database entirely?

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What is the function of the UNIQUE operator in SQL?

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Which type of relationship allows one entity to be associated with multiple instances of another entity?

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What is the primary purpose of normalization in database design?

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In an ER diagram, which symbol is used to represent an entity?

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Which of the following statements best describes the first normal form (1NF)?

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How are foreign keys typically represented in an ER diagram?

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Which step is NOT part of the ER model creation process?

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What does the third normal form (3NF) aim to eliminate?

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Flashcards

Primary Key (PK)

A column or set of columns used to uniquely identify each row in a table, ensuring every record is distinct. It prevents duplicate entries and maintains data integrity.

Foreign Key (FK)

A column or set of columns in one table that references the primary key of another table, creating a link between the two.

Relational Database

A database management system that stores and manages data in structured tables with rows and columns, allowing for relationships between different tables.

Entity-Relationship Diagram (ERD)

A diagram used to visualize the entities, attributes, and relationships within a database system, helping to plan and understand data structures.

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Data Integrity

Ensuring the accuracy and consistency of data in a database, often achieved through constraints and rules.

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SELECT Statement

The SELECT statement retrieves data from one or more tables.

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FROM Clause

The FROM clause specifies the table you want to get data from. It's like telling the database where to look.

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WHERE Clause

The WHERE clause filters rows based on a condition. It narrows down the results.

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INSERT Statement

The INSERT statement adds new records to the table.

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UPDATE Statement

The UPDATE statement modifies existing data in a table. Use a WHERE clause to specify which records to modify.

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DELETE Statement

The DELETE statement removes records from a table using a WHERE clause.

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JOIN Clause

A JOIN clause combines data from two or more tables based on a common column. It's like connecting pieces of a puzzle.

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INNER JOIN

An INNER JOIN retrieves matching records from both tables. It's like finding the overlap between two sets.

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Aggregate Function

An AGGREGATE FUNCTION is used to summarize data, derive insights and perform calculations on datasets. For example, SUM, AVG, MAX, MIN, COUNT.

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Relationship Definition

Describes how entities in a database are related to each other. It helps understand the interactions between various entities.

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One-to-One Relationship

A type of relationship where one instance of an entity can only be associated with one instance of another entity. Example: one person has one driver's license.

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One-to-Many Relationship

A type of relationship where one instance of an entity can be associated with multiple instances of another entity. Example: one school has many students.

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Many-to-one Relationship

A type of relationship where multiple instances of an entity can be associated with one instance of another entity. Example: many employees work in one store.

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Many-to-Many Relationship

A type of relationship where multiple instances of one entity can be associated with multiple instances of another entity. Example: many employees can enroll in many trainings, and many trainings can have many employees enrolled.

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Normalization

A process of organizing and structuring data in a database to reduce redundancy and improve data integrity. It involves eliminating redundancies, using primary and foreign keys, and reducing transitive dependencies.

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Database Design

The process of creating a detailed blueprint for how data will be stored, accessed, and managed in a database. It involves defining table structure, primary keys, foreign keys, and other constraints based on the ER diagram.

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Arithmetic Operations

Mathematical operations (+, -, *, /) applied to data in SQL queries. They let you perform calculations like finding discounted rates.

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Comparison Operators

Used to compare data in SQL queries (>, <, =, !=, LIKE). They help filter results based on specific conditions.

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LIKE Operator

A special comparison operator used for pattern matching in strings, often with wildcards (%) and (_). Useful for finding records containing specific patterns.

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Logical Operators

Operators used to combine multiple conditions in SQL queries (AND, OR, NOT). They help create complex filters for more precise data retrieval.

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String Functions

Functions that manipulate and transform text data in SQL queries. They allow you to concatenate, extract, format, and search within strings.

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Subqueries

A query placed inside another SQL query, enclosed in parentheses. They break down complex queries into smaller units, making them easier to understand and maintain.

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JOIN

Joining data from multiple tables based on a common column. Think of combining information from different sources.

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Concat Function

Used to combine multiple columns into a single string in SQL queries. It helps create combined data fields.

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Substring Function

A function that extracts a specific portion of a string in SQL queries, based on starting position and length.

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Study Notes

Introduction to Databases

  • Databases are essential for efficient data management in today's digital world, used across various industries like e-commerce, social media, finance, healthcare, and education.
  • Before databases, data was stored on paper, magnetic tapes, books, and electronic files.
  • These methods lacked efficiency in searching, retrieving, and managing large volumes.

Evolution of Databases

  • In the 1970s, the Entity-Relationship model was introduced as a database design standard tool.
  • Oracle introduced the first relational database management system (RDBMS) in the 1970s.
  • The 1980s saw the development of SQL as a standard language for RDBMS.
  • More companies developed RDBMS, including Sybase and the early Microsoft SQL Server.

Basic Concepts of Databases

  • A database is a collection of interrelated data organized for efficient access, management, and updating.
  • Databases consist of tables with rows (records) and columns (fields).
  • Data in one table can be related to other tables through relationships.
  • Databases can store information on various subjects such as people, products, or orders.
  • As data grows in a spreadsheet or word processing program, redundancies and inconsistencies arise.
  • Databases use DBMS (Database Management Systems) software for storage, retrieval, and manipulation of data.

The 3 Architecture Levels in a Database

  • Conceptual Design: a technology-agnostic design defining entities and relationships in a database.
  • Logical Level: detailing the structure (tables, columns) suitable for specific database management systems.
  • Physical Level: describing how data is physically stored in the system.

Database Management System (DBMS)

  • DBMS software manages databases.
  • It provides a user-friendly interface to interact with the databases.
  • Main functions include defining, creating, searching, updating and administering databases.
  • Examples of DBMS software include Oracle Database, Microsoft SQL Server, and MySQL.

Relational Databases

  • Store data in tables with rows and columns.
  • Use relationships between tables to link data.
  • Tables consist of attributes and rows of related instances.
  • Key concepts are Primary Keys (uniquely identifying rows) and Foreign Keys (creating links between tables).
  • Relational database designs are crucial for data integrity and reliability.

Entity-Relationship Diagrams (ERD)

  • ER diagrams visually display entity attributes and relationships.
  • Entities are represented by rectangles, attributes by ovals, and relationships by diamonds.

Normalization

  • Normalization is a process to organize and structure data in databases.
  • Eliminate data redundancies and improve data integrity.
  • Normal Forms (1NF, 2NF, 3NF) detail the data structure.

SQL (Structured Query Language)

  • A language for managing and manipulating relational databases.
  • SQL provides commands for creating, reading, updating, and deleting data.
  • Used in most relational databases.

Real-world Database Applications

  • Business Intelligence uses SQL to create reports.
  • Finance uses SQL for transaction processing and risk management
  • Healthcare uses SQL for patient records and data management.
  • Various businesses utilize SQL for e-commerce and inventory management.
  • Data analysis uses SQL to gain insights.

NoSQL Databases

  • Non-relational databases are used with larger sets of data and handle different data structures.
  • NoSQL databases are schema-less compared to relational databases.
  • They are horizontally scalable, accommodating vast data volumes.
  • They are suitable for various data types including structured, semi-structured, or unstructured.
  • NoSQL databases are preferable in handling real-time, big data applications, and data changing rapidly.

Types of NoSQL Databases

  • Document stores are used for content management systems and flexible data structures.
  • Key-value stores are suited for caching, session management, and real-time bidding.
  • Graph databases efficiently model and store highly connected data.

Using Microsoft Excel as a Database

  • Excel can be used as a simple database for smaller collections or prototypes.
  • Excel isn´t designed for a complex storage structure but can handle simple tables.
  • Data Relationships in Excel are important and require careful management of referential integrity.

Power BI as a Database Tool

  • Power BI is a tool to analyze and visualize data rather than a primary tool for data storage.
  • Power BI Desktop is a software installed on the computer to clean and transform data and connect to several sources.
  • Power BI Service is a cloud-based platform suitable for sharing data and collaborating.

Big Data

  • Big data is a term referring to large datasets with characteristics like volume, velocity, variety, veracity, and value.
  • Different tech (including relational and other formats) are used to process big data.
  • Variety of data formats and structures can be processed and integrated.

Economic and Financial Data Sources

  • Datasets like company financial records, transaction logs, and market indexes.
  • Government sources, central banks, and financial institutions also provide relevant data.

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