what are join types
INNER JOIN: is used when retrieving data from multiple tables and will return only matching data. LEFT OUTER JOIN: is used when retrieving data from multiple tables and will return left table and any matching right table records. RIGHT OUTER JOIN: is used when retrieving data from multiple tables and will return right table and any matching left table records FULL OUTER JOIN: is used when retrieving data from multiple tables and will return both table records, matching and non-matching.