Different types of Joins in SQL and what are the outputs when you join two tables with nulls.

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Different types of Joins in SQL and the outputs when joining two tables with nulls.

Types of joins in SQL include inner join, left join, right join, and full outer join.
When joining two tables with nulls, the output depends on the type of join used.
In an inner join, null values are excluded from the result.
In a left join, all rows from the left table and matching rows from the right table are included, with nulls for non-matching rows.
In a right join, all rows from the right table and matching rows from the left table are included, with nulls for non-matching rows.
In a full outer join, all rows from both tables are included, with nulls for non-matching rows.

Accepted Answer

In SQL, joins are used to combine data from two or more tables based on a common column between them. There are several types of joins, each with its own behavior and purpose. Let's explore the common types of joins and what happens when you join tables with null values:

INNER JOIN:
- Returns only the rows that have matching values in both tables.
- If there's no match between the tables, those rows are excluded from the result.
- Rows with null values in the joining column are excluded from the output.
LEFT JOIN (or LEFT OUTER JOIN):
- Returns all rows from the left table and the matching rows from the right table.
- If there's no match in the right table, null values are filled in for the columns from the right table.
- Rows with null values in the joining column of the left table are still included in the output.
RIGHT JOIN (or RIGHT OUTER JOIN):
- Returns all rows from the right table and the matching rows from the left table.
- If there's no match in the left table, null values are filled in for the columns from the left table.
- Rows with null values in the joining column of the right table are still included in the output.
FULL OUTER JOIN:
- Returns all rows from both tables, including the matching rows and the non-matching rows from each table.
- If there's no match in either table, null values are filled in for the columns from the table that doesn't have a match.

Now, let's consider what happens when you join two tables with null values:

Inner Join: Rows with null values in the joining column of either table will be excluded from the result since null is not considered a match.
Left Join: Rows with null values in the joining column of the right table will be included in the result, with null values filling the columns from the right table.
Right Join: Rows with null values in the joining column of the left table will be included in the result, with null values filling the columns from the left table.
Full Outer Join: Rows with null values in the joining column of either table will be included in the result, and columns from the table that doesn't have a match will be filled with null values.

Different types of Joins in SQL and what are the outputs when you join two tables with nulls.

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