Explain the difference between INNER JOIN and LEFT JOIN in Postgresql.

Understanding the difference between INNER JOIN and LEFT JOIN in Postgresql

When working with relational databases in Postgresql, it is crucial to understand the distinction between INNER JOIN and LEFT JOIN to effectively retrieve data from multiple tables.

INNER JOIN

The focus keyword "INNER JOIN" pertains to a type of join operation that returns only the rows where there is a match found in both tables based on the specified join condition. In other words, INNER JOIN selects and combines rows from two tables that have matching values in the joined columns. Records that do not have a match in both tables will be excluded from the result set.

LEFT JOIN

The focus keyword "LEFT JOIN" refers to another type of join in Postgresql that retrieves all the rows from the left table along with the matched rows from the right table. If there is no match found in the right table, NULL values are appended to the result set. This means that even if there are unmatched rows in the left table, they will still be included in the output when using a LEFT JOIN.

Therefore, the main difference between INNER JOIN and LEFT JOIN lies in how they handle unmatched rows. While INNER JOIN excludes unmatched rows, LEFT JOIN includes them with NULL values for the columns of the right table.

It is essential to choose the appropriate join type based on the requirements of your query to ensure accurate and efficient data retrieval from multiple tables in Postgresql.