What is the difference between INNER JOIN and OUTER JOIN ?

The difference between INNER JOIN and OUTER JOIN in SQL lies in how they handle the rows from the tables being joined and the results they produce.

INNER JOIN

• Definition: An INNER JOIN returns only the rows that have matching values in both tables. It combines rows from two or more tables based on a related column between them.
• Result Set: Only the rows that meet the join condition from both tables are included in the result set. If a row in one table does not have a matching row in the other table, that row will not be included.
• Syntax:
  sql Copy

  SELECT columns
  FROM table1
  INNER JOIN table2
  ON table1.column_name = table2.column_name;

• Performance: Generally faster than OUTER JOINs because it only processes matching rows[1][4][6].

OUTER JOIN

• Definition: An OUTER JOIN returns all rows from one table and the matching rows from another table. If there is no match, NULL values are included for columns from the non-matching table.
• Types:
  • LEFT OUTER JOIN: Returns all rows from the left table and the matched rows from the right table. If no match is found, NULL values are returned for columns from the right table.
  • RIGHT OUTER JOIN: Returns all rows from the right table and the matched rows from the left table. If no match is found, NULL values are returned for columns from the left table.
  • FULL OUTER JOIN: Returns all rows when there is a match in either left or right table. If there is no match, NULL values are included for columns from the non-matching table.
• Syntax:
  sql Copy

  -- LEFT OUTER JOIN
  SELECT columns
  FROM table1
  LEFT OUTER JOIN table2
  ON table1.column_name = table2.column_name;
  
  -- RIGHT OUTER JOIN
  SELECT columns
  FROM table1
  RIGHT OUTER JOIN table2
  ON table1.column_name = table2.column_name;
  
  -- FULL OUTER JOIN
  SELECT columns
  FROM table1
  FULL OUTER JOIN table2
  ON table1.column_name = table2.column...