Updating my branch with main

Topics/Tech_Stacks/SQL-creating_database.md

@@ -0,0 +1,109 @@
+# Understanding SQL Schemas, Database Creation, and Best Practices for Optimal Setup
+
+## Table of Contents
+1. [Introduction to SQL](#introduction-to-sql)
+2. [Understanding Schema in SQL](#understanding-schema-in-sql)
+3. [Steps for Basic Database Creation](#steps-for-basic-database-creation)
+    1. [How to create a schema](#how-to-create-a-schema)
+    2. [How to create tables in the schema](#how-to-create-tables-in-the-schema)
+    3. [Datatypes](#datatypes)
+    4. [Reaction policies](#reaction-policies)
+4. [Best Practices for Database Structure](#best-practices-for-database-structure)
+
+### Introduction to SQL
+SQL also known as Structured Query Language is a programming language used to store and process information in a relational database.
+When working with databases in your projects, it is a very helpful language to easily manage and manipulate data.
+It also integrates well with different programming languages making it a very efficient tool.
+
+To learn more about what SQL is, check out [What is SQL (Structured Query Language)?](https://aws.amazon.com/what-is/sql/#:~:text=Structured%20query%20language%20(SQL)%20is,relationships%20between%20the%20data%20values).
+
+### Understanding Schema in SQL
+In a SQL database, a schema is a list of logical structures of data. It's a way to organize and manage database objects. A schema helps to segregate and structure the database by providing a namespace for these objects.
+
+It allows different users or applications to have their own space within the database without conflicting with each other's objects.
+
+To read more about schema and their advantages, you can check out
+[What Is a Schema in SQL and Advantages of Using Schema](https://www.simplilearn.com/tutorials/sql-tutorial/schema-in-sql#:~:text=MEANExplore%20Program-,What%20is%20Schema%20in%20SQL%3F,user%20who%20constructs%20the%20object).
+
+### Steps for Basic Database Creation
+
+#### How to create a schema
+The first step of a good database creation should be to initialize a schema.
+<br>
+You can do so by using the query 
+<br>CREATE SCHEMA <schema name>; <br>
+and then alter the schema to add tables to it.
+
+You can alternatively use,<br>
+CREATE SCHEMA <schema name> <br>
+CREATE TABLE table_name (...);
+
+#### How to create tables in the schema
+A table is a fundamental structure used to store data in a relational database. It consists of rows and columns where each column represents a different attribute, and each row represents a record or an entry in the table
+
+The syntax to create a table is
+<br>
+CREATE TABLE <tablename> (
+<br>
+<column1_name column1_datatype other_attributes,
+<br>
+column2_name column2_datatype other_attributes,
+<br>
+...);
+
+Example : <br>
+CREATE SCHEMA University<br>
+CREATE TABLE Students(<br>
+    utorid varchar(8),<br>
+    fname varchar(15),<br>
+    lname varchar(15)<br>
+);
+
+![example_table_creation](https://github.com/learning-software-engineering/learning-software-engineering.github.io/assets/113269746/98cfb7cb-731b-49da-bb9b-b1bf5e9ba087)
+
+Additional Resources :<br>
+https://www.w3schools.com/sql/sql_create_table.asp <br>
+https://www.w3schools.com/sql/sql_alter.asp
+
+#### Datatypes
+SQL has a range of datatypes your column can have.
+
+Check https://www.w3schools.com/sql/sql_datatypes.asp for the list of datatypes, their description and storage.
+
+#### Reaction policies
+Reaction policies are actions defined on a database level to manage referential integrity constraints, especially when a referenced record is affected by a change (update or delete).
+Some of the most common reaction policies are :
+- CASCADE<br>
+  This action replicates the same changes (update or delete) to the related rows automatically. For example, if a record in a parent table is deleted, CASCADE will automatically delete all related records in the child table that reference the deleted record.
+- SET NULL<br>
+  With this action, if a referenced record is deleted or updated, the foreign key columns in the referencing table are set to NULL.
+- RESTRICT<br>
+  This action prevents changes that would violate referential integrity. For example, it prevents the deletion or update of a referenced record if there are still related records in the referencing table.
+
+### Best Practices for Database Structure
+When it comes to practices, there are a lot of practices that one can adopt in order to build a nice and efficient. Here are some of the main things to keep in mind while building a database.
+
+1. Avoid redundancy
+
+Redundancy refers to the unnecessary repetition or duplication of data within a database. Redundancy can occur when the same data is stored in multiple places or when unnecessary columns are present in a table.
+<br>
+There are many ways to reduce redundancy and one of the ways is to normalize your data. There are algorithms like BCNF Decomposition, 3CNF etc. which can be useful.
+
+Additional Resources:
+- https://www.mydbsync.com/blogs/ways-to-reduce-data-redundancy/
+- https://www.linkedin.com/advice/1/how-do-you-normalize-your-data-reduce-redundancy
+
+2. Use primary and foreign keys
+
+A primary key is a key used to uniquely identify a row in a table and cannot have NULL values.
+<br>
+A foreign key is a key that refers to a column in a relational database table that provides a link between data in two tables. It is a column (or columns) that references a column (most often the primary key) of another table.
+<br>
+Utilize these keys effectively to establish relationships between tables, enforcing data integrity and ensuring referential integrity.
+
+3. Use consistent naming conventions
+
+
+4. Construct your schema with the intention of minimizing the presence of nullable attributes.
+
+These are just some ideas and tips to create a basic schema. SQL is a very powerful languages, and you can do a lot more using it!