Structured Query Language (SQL)| Full Explanation (Definition, usage, structure and example with MySQL)
Tags: sql, database, development
Published: 2023-07-03 23:24:39

Structured Query Language (SQL)| Full Explanation (Definition, usage, structure and example with MySQL)

# Introduction

Hello, my name is Daniela Barazarte and I want to welcome you to this complete explanation of SQL. This explanation will be intuitive and simple as well as all the explanations that are part of #DetectaLaLogica.

If you prefer videos, here is a full tutorial made by me on YouTube, it's in Spanish but it also has subtitles: https://youtu.be/Hjs-zGEQtg8

# <u>Theory</u>
## Definition of each word
**Structured Query Language (SQL) or Structured Query Language**
- Language: refers to the set of rules and syntax used to write programs that a computer can understand.
- Structured: means to organize the code of a program in smaller and more logical pieces, so that it is easier to understand and maintain.
- Query: refers to a specific search for information in a database.

## Full definition
SQL is a programming language used to manage and manipulate structured and relational databases using queries.


![SQL Database](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/c4hlfjkg6gio7bbrut5t.png)

## #DetectTheLogic
SQL is called Structured Query Language (Structured Query Language) because it is literally a language that allows us to query a structured database and obtain results

# <u>Use</u>
## So that
It is used to manage and manipulate relational databases, either to create, modify, delete, or view tables, objects, and records in a database.

## When and where
- E-commerce websites
- Content management applications
- Social media apps
- Data analysis applications
- Project management applications
- Booking and appointment apps

## As
You need a relational database management system that supports SQL (MySQL, Oracle, Microsoft SQL Server, etc.) Then, you must use the commands

# <u>Practice</u>
## Exercise
You have a web application for an online store that sells electronics. You must store and manage order information.

### **Method: SQL**

```
-- Create the order table
CREATE TABLE orders (
   id INT AUTO_INCREMENT PRIMARY KEY,
   client VARCHAR(50) NOT NULL,
   date DATE NOT NULL,
   product VARCHAR(50) NOT NULL,
   amount INT NOT NULL,
   price DECIMAL(10,2) NOT NULL
);

-- Create orders
INSERT INTO orders (customer, date, product, quantity, price)
VALUES
   ('Juan Perez', '2023-06-16', 'Red shirt', 2, 20.50),
   ('Ana Garcia', '2023-06-15', 'Blue pants', 1, 35.00),
   ('Luis Gomez', '2023-06-15', 'Green dress', 2, 40.00),
   ('Maria Hernandez', '2023-06-14', 'Bob Grapefruit Socks', 12, 5.80),
   ('Carlos Rodriguez', '2023-06-14', 'Jacket for the cold', 1, 75.50),
   ('Laura Martinez', '2023-06-13', 'Blue Blouse', 3, 30.20),
   ('Pedro Sanchez', '2023-06-13', 'Cowboy Jeans', 6, 50.00),
   ('Sofia Ramirez', '2023-06-12', 'Sweatshirt for exercise', 2, 25.80),
   ('Diego Torres', '2023-06-12', 'Crocodile Cap', 1, 12.80),
   ('Fernanda Castro', '2023-06-11', 'Coat', 2, 90.00);

-- Read all orders
SELECT * FROM orders;

-- Read order by ID
SELECT * FROM orders WHERE id = 3;

-- Edit/Update Order
UPDATE orders SET quantity = 4, price = 80.00 WHERE id = 5;

-- Delete order
DELETE FROM orders WHERE id IN (2, 6, 8);
```

# Importance
**SQL has several benefits:**

- It is easy to learn and use.
- It is very efficient to manipulate and access data.
- It is flexible and can handle both simple and complex queries.
- It is scalable, it works with small or very large databases.
- It is a de facto standard, widely compatible between different database systems.
- Once you master it, you can apply your skills to multiple database platforms.

# Farewell
(Remember) #DetectaLaLógica: SQL is called Structured Query Language (Structured Query Language) because it is literally a language that allows us to query a structured database and obtain results

You can practice this topic in my GitHub repository (C# language code): https://github.com/danielabarazarte/DetectaLaLogica

Thank you very much for reading, if you have any questions you can comment and you can also follow me to see more posts of this style, thanks <3.