Sql Joins Notes Pdf -

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

📊 Intersection of A and B. 3.2 LEFT JOIN (or LEFT OUTER JOIN) Returns ALL rows from the left table, matched rows from the right table. NULL if no match. sql joins notes pdf

📊 Union of A and B. 3.5 CROSS JOIN Cartesian product – every row in A paired with every row in B. (Use with caution!) | student_id | course | |------------|-----------| | 1

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 | NULL if no match

SELECT * FROM students RIGHT JOIN courses ON students.id = courses.student_id; | id | name | student_id | course | |------|-------|------------|---------| | 1 | Alice | 1 | Math | | 2 | Bob | 2 | Science | | NULL | NULL | 4 | Art | RIGHT JOIN is less common; you can usually rewrite it as a LEFT JOIN by swapping table order. 3.4 FULL OUTER JOIN Returns ALL rows from both tables. Matches where available, NULL elsewhere.

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