30.10.2024

Basic SQL Commands

SQL (Structured Query Language) is the standard language used to interact with relational databases. Whether you’re working with MySQL, PostgreSQL, or SQLite, SQL provides the essential commands needed to create, manage, and manipulate databases.

In this article, we’ll cover the basic SQL commands every beginner should know.

1. SELECT

The SELECT statement is used to retrieve data from a database. You can specify which columns to select and which table to query:

SELECT column1, column2 FROM table_name;

Example:

SELECT first_name, last_name FROM employees;

2. INSERT INTO

The INSERT INTO statement is used to insert new records into a table:

INSERT INTO table_name (column1, column2) VALUES (value1, value2);

Example:

INSERT INTO employees (first_name, last_name) VALUES (‘John’, ‘Doe’);

3. UPDATE

The UPDATE statement is used to modify existing records in a table:

UPDATE table_name SET column1 = value1 WHERE condition;

Example:

UPDATE employees SET last_name = ‘Smith’ WHERE id = 1;

4. DELETE

The DELETE statement is used to remove records from a table:

DELETE FROM table_name WHERE condition;

Example:

DELETE FROM employees WHERE id = 1;

5. CREATE TABLE

The CREATE TABLE statement is used to create a new table in the database:

CREATE TABLE table_name ( column1 datatype, column2 datatype, … );

Example:

CREATE TABLE employees ( id INT PRIMARY KEY, first_name VARCHAR(50), last_name VARCHAR(50) );

6. ALTER TABLE

The ALTER TABLE statement is used to modify an existing table, such as adding or deleting columns:

ALTER TABLE table_name ADD column_name datatype;

Example:

ALTER TABLE employees ADD email VARCHAR(100);

7. DROP TABLE

The DROP TABLE statement is used to delete an entire table from the database:

DROP TABLE table_name;

Example:

DROP TABLE employees;

8. WHERE Clause

The WHERE clause is used to filter records in a query based on a condition:

SELECT * FROM table_name WHERE condition;

Example:

SELECT * FROM employees WHERE first_name = ‘John’;

Conclusion

These basic SQL commands form the foundation of database management and data manipulation. By mastering these commands, you can create, update, delete, and query data in relational databases. As you gain more experience, you can explore more advanced SQL features like joins, indexes, and transactions.