SQL: Key Concepts You Should Know

SQL (Structured Query Language) is a standard programming language used for managing and manipulating relational databases.

Photo by Caspar Camille Rubin on Unsplash

Aliases Aliases are like shortcuts for making your SQL queries easier to read. They give temporary names to tables or columns.

For example:

SELECT name AS employee_name FROM employees;

GROUP BY The GROUP BY clause helps you summarize data by grouping rows that have the same values in specified columns.

For example:

SELECT department, COUNT() AS num_employees FROM employees GROUP BY department;*

ORDER BY Use ORDER BY to sort your query results. You can sort data in ascending (ASC) or descending (DESC) order:

SELECT name, salary FROM employees ORDER BY salary DESC;

JOINS Joins combine rows from two or more tables based on related columns. Common types include:

-INNER JOIN: Shows rows with matching values in both tables. -LEFT JOIN: Shows all rows from the left table and matched rows from the right table.

SELECT employees.name, departments.department_name FROM employees INNER JOIN departments ON employees.department_id = departments.department_id;

Functions SQL functions perform operations on your data. Examples are: -Aggregate Functions: COUNT, SUM, AVG -String Functions: CONCAT, SUBSTRING

SELECT AVG(salary) AS average_salary FROM employees;

WHERE Clause The WHERE clause filters data based on conditions you specify:

SELECT name, salary FROM employees WHERE salary > 50000;

Mastering these SQL basics will make working with data much smoother.