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If you are venturing into the world of SQL, one thing you inevitably will come across are SQL Joins. They are integral to combining data from two or more tables based on related columns between them. In this blog post, we will dive deep into one specific type of join: the Full Outer Join, exploring its functionality, and illustrating with some examples.
What is a Full Outer Join?
In SQL, a Full Outer Join combines the results of both left and right outer joins. The joined table will contain all records from both tables and fill in NULLS for missing matches on either side.
Basic Syntax
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SELECT column_name(s) FROM table1 FULL OUTER JOIN table2 ON table1.column_name = table2.column_name; |
In this syntax, the full outer join returns all records when there is a match in either table1 or table2.
SQL Full Outer Join Example
Let’s assume we have two tables. The first table is the ‘Orders’ table:
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SELECT * FROM Orders; |
And the ‘Customers’ table:
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SELECT * FROM Customers; |
Now let’s perform a Full Outer Join on these tables:
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SELECT Orders.OrderID, Customers.CustomerName FROM Orders FULL OUTER JOIN Customers ON Orders.CustomerID = Customers.CustomerID; |
This SQL statement would return all order IDs and customer names whenever there is a match in either table. If there is no match, the missing side will contain NULL.
Working with NULL Values
When performing a Full Outer Join, NULL Values can occur. Here is how to manage them:
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SELECT Orders.OrderID, ISNULL(Customers.CustomerName, 'No Customer') FROM Orders FULL OUTER JOIN Customers ON Orders.CustomerID = Customers.CustomerID; |
This command uses the ISNULL function to replace the NULL values with ‘No Customer’ in the result set.
Conclusion
A Full Outer Join in SQL can be a powerful tool when you need to combine data from two tables. It gives you the flexibility to get all records, matched or not, from the tables involved, providing a comprehensive overview of your data. Remember that practice is the key to mastering any concept in SQL, so don’t be shy to create your own examples and experiment with different types of data to fully grasp the functionality of Full Outer Joins.
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