What is SQL?
SQL (Structured Query Language) is the standard language for managing and manipulating databases. Whether you want to retrieve data, insert new records, update existing data, or delete unnecessary entries.
Essential SQL Keywords
Understanding SQL keywords is fundamental to writing effective queries. Here are some of the most commonly used SQL keywords:
- SELECT: Retrieve data from a database.
- FROM: Specify the table to query data from.
- WHERE: Filter records based on specified conditions.
- INSERT INTO: Add new records to a table.
- UPDATE: Modify existing records.
- DELETE: Remove records from a table.
Data Types
Data types define the kind of data that can be stored in a table. Here are some basic SQL data types you should know:
- INT: Integer numbers.
- VARCHAR: Variable-length strings.
- TEXT: Long text strings.
- DATE: Dates.
- FLOAT: Floating-point numbers.
- BOOLEAN: True/false values.
Basic Operations
Let’s explore some fundamental SQL operations through practical examples.
SELECT Statement
The SELECT statement is used to fetch data from a database. Here’s a simple example:
SELECT first_name, last_name FROM employees
WHERE department = 'Sales';
This query retrieves the first and last names of employees in the Sales department.
INSERT Statement
The INSERT INTO statement adds new records to a table. Here’s how you can add a new employee:
INSERT INTO employees (first_name, last_name, department, salary)
VALUES ('John', 'Doe', 'Marketing', 160000);
This command inserts a new employee named John Doe into the Marketing department with a salary of 160,000.
UPDATE Statement
The UPDATE statement modifies existing records. Suppose you need to update an employee’s salary:
UPDATE employees SET salary = 165000
WHERE first_name = 'John' AND last_name = 'Doe';
This updates John Doe’s salary to 165,000.
DELETE Statement
The DELETE statement removes records from a table. Here’s how to delete an employee record:
DELETE FROM employees WHERE first_name = 'John' AND last_name = 'Doe';
This deletes John Doe’s record from the employees table.
Conclusion
Mastering basic syntax is the first step towards becoming proficient in database management. Practice these fundamental operations and experiment with different queries to deepen your understanding. Happy querying!
Learn more on SQL data definition language (DDL).
