Do you know how to perform joins in SQL?

To perform a join in SQL, you write a SELECT statement that references two or more tables and specifies the join type and condition. For example:

SELECT a.id, a.name, b.salary
FROM employees a
INNER JOIN salaries b ON a.id = b.emp_id;

This inner join returns only employees that have a matching salary record. You can replace INNER with LEFT, RIGHT, or FULL to include unmatched rows. The ON clause defines the join key; you can use multiple conditions or inequalities for more complex logic. For cross joins, omit the ON clause:

SELECT * FROM table1 CROSS JOIN table2;

Remember to alias tables for readability and to avoid column name conflicts. Using proper indexes on join columns improves performance, especially for large tables.