Introduction to SQL
SQL (Structured Query Language) is a standard language used to manage and manipulate relational databases. With SQL, we can perform various operations such as reading data, inserting data, updating data, and deleting data from a database.
Why Learn SQL?
SQL is used in almost every modern system, such as:
- POS (Point of Sale) applications
- Banking systems
- Marketplaces
- Analytics dashboards
- Backend APIs
- Inventory and warehouse systems
Understanding SQL is an essential foundation for backend developers, data analysts, and software engineers.
Main SQL Functions
Some of the main SQL commands include:
| Command | Function |
|---|---|
SELECT | Retrieve data |
INSERT | Add data |
UPDATE | Modify data |
DELETE | Remove data |
CREATE | Create table/database |
ALTER | Modify table structure |
DROP | Delete table/database |
SQL Query Examples
Retrieving Data
SELECT * FROM users;
Inserting Data
INSERT INTO users (name, email)
VALUES ('Akmad', 'akmad@mail.com');
Updating Data
UPDATE users
SET name = 'Nudin'
WHERE id = 1;
Deleting Data
DELETE FROM users
WHERE id = 1;
Be careful when using DELETE without a WHERE clause. It may remove all data in a table.
Relational Database Structure
A relational database consists of several components:
Components
- Database → Main storage container
- Table → Collection of data
- Row → A single record of data
- Column → Data field structure
- Primary Key → Unique identifier for data
- Foreign Key → Relationship between tables
Conclusion
SQL is a fundamental skill that should be understood in modern software development. By learning SQL, we can manage data efficiently, quickly, and in a structured way.
Additional notes will be created in each module according to tasks needed in a working environment.