The document discusses different types of JOIN operations in SQL including: - INNER JOIN, which combines records from two tables based on common values and returns matched records - OUTER JOIN, which returns all records from one or both tables even if they do not meet the join condition - LEFT and RIGHT OUTER JOINs return all records from the left or right table respectively - SEMI JOIN returns records from the left table that have matching records in the right table - THETA JOIN allows a more general join condition specified by a binary operator like less than, greater than, etc.