Understanding INNER JOIN and OUTER JOIN in SQL

Focus keyword: INNER JOIN and OUTER JOIN

In SQL, INNER JOIN and OUTER JOIN are both used to combine rows from different tables based on a related column between them. The main difference between the two is:

• INNER JOIN: This type of join returns only the rows where there is a match between the columns in both tables. It excludes unmatched rows from the result set.
• OUTER JOIN: On the other hand, OUTER JOIN returns all rows from at least one of the tables being joined, along with matching rows from the other table (if any). There are different types of OUTER JOINs such as LEFT OUTER JOIN, RIGHT OUTER JOIN, and FULL OUTER JOIN.

When deciding which type of join to use in a given situation, consider the following:

• Use INNER JOIN:
  • When you only want to retrieve rows that have matching values in both tables.
  • For scenarios where you need to retrieve data from two related tables where a match is mandatory.
• Use OUTER JOIN:
  • When you want to include unmatched rows from one or both tables in the result set.
  • For situations where you need to retrieve data from one table, even if there are no corresponding rows in the other table.

By understanding the differences between INNER JOIN and OUTER JOIN and considering the specific requirements of your query, you can effectively choose the appropriate join type to use in SQL.