Day - 1 of SQL for Data Science

In today's data-driven world, SQL remains a foundational tool for data professionals, empowering them to extract valuable insights from databases. I've put together a comprehensive guide in this article to help you understand the significance of mastering some basic SQL queries.

Structured Query Language (SQL)

SQL is a domain-specific programming language used for managing and manipulating relational databases. It provides a standardized way to interact with databases, allowing users to create, retrieve, update, and delete data within them. SQL is widely used in the field of data management and plays a fundamental role in data-related tasks such as data analysis, data reporting, and database administration.

Key features of SQL include :

• Data Querying : SQL enables users to retrieve specific data from one or more tables in a database using queries. These queries can include various clauses like SELECT, FROM, WHERE, GROUP BY, HAVING, and ORDER BY to filter, sort, and aggregate data.
• Data Modification : SQL allows users to insert, update, and delete data in the database using INSERT, UPDATE, and DELETE statements, respectively. This functionality ensures data can be modified as needed while maintaining data integrity and consistency.
• Database Schema Definition : SQL provides commands to create and manage database schemas, including creating tables, defining relationships between tables (foreign keys), and setting constraints to maintain data accuracy and completeness.
• Data Manipulation Language (DML) : SQL includes commands for manipulating data in the database, such as SELECT, INSERT, UPDATE, and DELETE. These statements form the core of data manipulation tasks.
• Data Definition Language (DDL) : SQL's DDL commands facilitate the creation, modification, and deletion of database structures, including tables, views, indexes, and constraints.
• Data Control Language (DCL) : SQL provides DCL commands to manage user permissions and access control to databases, ensuring data security and privacy.

SQL is implemented by various database management systems (DBMS) such as MySQL, PostgreSQL, Oracle, Microsoft SQL Server, and SQLite, among others. While SQL syntax may vary slightly between different DBMS, the core concepts and capabilities remain consistent, making it a portable and widely applicable language for database management.

Advantages of SQL

There are some major advantages to using traditional relational databases, which we interact with using SQL.

The five most apparent are :

• SQL is easy to understand.
• Traditional databases allow us to access data directly.
• Traditional databases allow us to audit and replicate our data.
• SQL is a great tool for analyzing multiple tables at once.
• SQL allows you to analyze more complex questions than dashboard tools like Google Analytics.

Why Businesses Like Databases

• Data integrity is ensured - only the data you want entered is entered, and only certain users are able to enter data into the database.
• Data can be accessed quickly - SQL allows you to obtain results very quickly from the data stored in a database. Code can be optimized to quickly pull results.
• Data is easily shared - multiple individuals can access data stored in a database, and the data is the same for all users allowing for consistent results for anyone with access to your database.

How Databases Store Data

A few key points about data stored in SQL databases:

• Data in databases is stored in tables that can be thought of just like Excel spreadsheets.
• All the data in the same column must match in terms of data type.
• Consistent column types are one of the main reasons working with databases is fast.

Database SQL File and ERD Diagram

From Udacity, I have downloaded the ERD Diagram and the SQL File of "The Parch and Posey Database" which you need while writting queries related to SQL Concepts.

Entity Relationship Diagrams (ERD)

An entity relationship diagram is a common way to view data in a database. Below is the ERD for the database we will use from Parch & Posey. These diagrams help you visualize the data you are analyzing including:

1. The names of the tables.
2. The columns in each table.
3. The way the tables work together.

SQL Database File

Install all the requirements and understand the ERD Diagram of "The Parch and Posey Databse".

From tommarow we will start our journey of SQL and we will write some queries.