SQL Basics - A Beginner's Guide

1. Creating a Table

Use the CREATE TABLE command to define a new table.

CREATE TABLE employees (
    id INT PRIMARY KEY,
    name VARCHAR(50),
    age INT,
    department VARCHAR(50),
    salary DECIMAL(10,2)
);

2. Inserting Data

Add records using INSERT INTO.

INSERT INTO employees (id, name, age, department, salary)
VALUES 
(1, 'Alice', 28, 'HR', 50000.00),
(2, 'Bob', 34, 'IT', 70000.00),
(3, 'Charlie', 25, 'Finance', 60000.00);

Table After Insertion:

ID Name Age Department Salary
1 Alice 28 HR 50000.00
2 Bob 34 IT 70000.00
3 Charlie 25 Finance 60000.00

3. Retrieving Data

Use SELECT * FROM to view all records.

SELECT * FROM employees;

4. Updating Data

Modify a record using UPDATE.

UPDATE employees SET salary = 75000 WHERE id = 2;

Table After Update:

ID Name Age Department Salary
1 Alice 28 HR 50000.00
2 Bob 34 IT 75000.00
3 Charlie 25 Finance 60000.00

5. Deleting a Record

Remove an employee using DELETE.

DELETE FROM employees WHERE id = 1;

Table After Deletion:

ID Name Age Department Salary
2 Bob 34 IT 75000.00
3 Charlie 25 Finance 60000.00

6. Counting Records

Find the total number of employees.

SELECT COUNT(*) FROM employees;

Output:

2

7. Sorting Data

Sort employees by salary in descending order.

SELECT * FROM employees ORDER BY salary DESC;

8. Deleting the Table

Use DROP TABLE to remove a table.

DROP TABLE employees;