Sql Joins Notes Pdf Apr 2026

SELECT e.name, d.dept_name FROM employees e JOIN departments d ON e.dept_id = d.dept_id; Assume two tables:

| student_id | course | |------------|-----------| | 1 | Math | | 2 | Science | | 4 | Art | Returns only rows with matching keys in BOTH tables.

SELECT * FROM students INNER JOIN courses ON students.id = courses.student_id; | id | name | student_id | course | |----|-------|------------|---------| | 1 | Alice | 1 | Math | | 2 | Bob | 2 | Science | sql joins notes pdf

| id | name | |----|---------| | 1 | Alice | | 2 | Bob | | 3 | Charlie |

1. What is a JOIN? A JOIN clause is used to combine rows from two or more tables based on a related column between them. SELECT e

Document Version 2.0 – Last updated: 2026-04-17

📊 Union of A and B. 3.5 CROSS JOIN Cartesian product – every row in A paired with every row in B. (Use with caution!) A JOIN clause is used to combine rows

SELECT * FROM students FULL OUTER JOIN courses ON students.id = courses.student_id; | id | name | student_id | course | |------|---------|------------|---------| | 1 | Alice | 1 | Math | | 2 | Bob | 2 | Science | | 3 | Charlie | NULL | NULL | | NULL | NULL | 4 | Art |