What is sql

Structured Query Language is a domain-specific language used to manage data, especially in a relational database management system.It allows users to delete,update,insert and retrive data.

Purpose of SQL

• Store Data: Organize data in tables.

• Retrieve Data: Fetch specific records using queries.

• Update Data: Modify existing records.

• Delete Data: Remove unnecessary records.

• Manage Permissions: Control user access to the database.

Places where we can code SQL

SQL Fiddle – For testing SQL queries online

DB Fiddle – Supports multiple SQL dialects

Mode Analytics – For data analysis using SQL

W3Schools SQL Tryit Editor – For basic SQL practice

Basic SQL Commands:

Create a Table:

CREATE TABLE Students (

    ID INT PRIMARY KEY,

    Name VARCHAR(50),

    Age INT

);

Insert Data:
sql

INSERT INTO Students (ID, Name, Age) VALUES (1, 'John', 14);

Retrieve Data:
SELECT * FROM Students;

Update Data:
UPDATE Students SET Age = 15 WHERE ID = 1;

3. 
   

4. Delete Data:
   DELETE FROM Students WHERE ID = 1;

Joins in sql:

1. INNER JOIN (Only Matching Records)

• Returns only the rows where there is a match in both tables.

Example:

SELECT customers.id, customers.name, orders.order_id

FROM customers

INNER JOIN orders ON customers.id = orders.customer_id;

2. LEFT JOIN (All from Left Table + Matches from Right Table)

• Returns all rows from the left table, and matching rows from the right table. If there's no match, NULL is returned for the right table's columns.

Example:

SELECT customers.id, customers.name, orders.order_id

FROM customers

LEFT JOIN orders ON customers.id = orders.customer_id;