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What is SQL? Structured Query Language (SQL) is a standard programming language designed for managing and manipulating data in relational databases. It allows users to create, read, update, and delete (CRUD operations) data within a database. SQL is essential for anyone working with databases, from software developers to data analysts. Key Components of SQL Database: A collection of organized/unorganized data that can be easily stored, accessed, managed, and updated. Table: A collection of related data entries consisting of rows and columns Row: A single record in a table is called a Row. Column: A single field in a table that contains all data of a specific type (or same type) is called a Column Basic SQL Commands 1. Creating a Database and a Table - Creating a database CREATE DATABASE Database_Name; -- Using the database USE Databse_Name; -- Creating a table CREATE TABLE Table_Name ( Attribute_Name Data_Type ); 2. Inserting Data -- Inserting data into the table INSERT INTO Table_Name (attribute1, attribute2) VALUES (Value1, value2); 3. Querying Data -- Selecting all data from the table SELECT * FROM Table_Name; -- Selecting specific columns from the table SELECT Attribute1, Attribute2 FROM Table_Name; 4. Updating Data -- Updating data in the table UPDATE Table_Name SET Attribute1 = 'Value' WHERE Attribute = Value; 5. Deleting Data -- Deleting data from the table DELETE FROM Table_Name WHERE Attribute = value; For eg:- // Create DataBase Create DATABASE mydatabase; // Select DataBase to use it USE mydatabase; // Create table CREATE TABLE employee { id INT, first_name VARCHAR(50), last_name VARCHAR(50), email VARCHAR(100) }; // Inserting Data INSERT INTO employee (id, first_name, last_name, email) VALUES (1, ‘Virat’, ‘Kohli’, ‘Virat265@example.com’) , (2, ‘Rohit’, ‘Sharma’, ‘Rohit@example.com’); //Querying Data SELECT * FROM employee; SELECT first_name, last_name FROM employee; // Updating Data UPDATE employee SET email = 'Virat.Kohli@example.com' WHERE id = 1; // Deleting Data DELETE FROM employee WHERE id = 2; Advanced SQL Concepts 1. Joins Joins are used to combine rows from two or more tables based on a related column. -- Inner Join SELECT employees.first_name, departments.department_name FROM employee INNER JOIN departments ON employee.department_id = departments.id; 2. Aggregate Functions Aggregate functions perform calculations on a set of values and return a single value. -- COUNT SELECT COUNT(*) FROM employee; -- SUM SELECT SUM(salary) FROM employee; -- AVG SELECT AVG(salary) FROM employee; -- MAX SELECT MAX(salary) FROM employee; -- MIN SELECT MIN(salary) FROM employee; 3. Subqueries A subquery is a query which is written within another query. -- Subquery to find employees with salaries above average SELECT * FROM employee WHERE salary > (SELECT AVG(salary) FROM employee); 4. Indexes Indexes improve the speed of data retrieval operations on a table at the cost of additional storage space and slower writes. -- Creating an index on the email column CREATE INDEX idx_email ON employee (email); Best Practices Normalization: It is used to reduce data redundancy and maintain data integrity. Indexing: Use indexes to speed up queries without over-indexing. Backup: Regularly backup your database to prevent data loss. Security: Implement proper security measures to protect your data, such as using strong passwords and encrypting sensitive data. Conclusion SQL is a powerful tool for managing and manipulating relational databases. By mastering its basic and advanced features, you can efficiently handle large datasets and perform complex queries. This guide provides a basic knowledge about what SQL is and basic SQL commands, but continued practice and learning are essential to becoming proficient in SQL. Happy querying!

Tag: database

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