Sql Joins Notes Pdf May 2026

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.

-- Query: Books with author names SELECT b.title, a.name FROM books b LEFT JOIN authors a ON b.author_id = a.id; sql joins notes pdf

📊 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

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