SQL for Beginners and Data Analyst – Chapter 28: cross apply, outer apply

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SQL, or Structured Query Language, is a widely used language in the field of data analysis and management. As a beginner in SQL, it’s important to learn the various functions and commands that you can use to effectively manage and extract insights from data. Two important functions to be aware of are the CROSS APPLY and OUTER APPLY functions.

CROSS APPLY and OUTER APPLY are functions used to join data from two tables in a database. The key difference between these two functions is the way that they handle missing data.

The CROSS APPLY function returns only the rows from the first table that have matching rows in the second table. If there’s no matching row in the second table, the row from the first table is not returned in the result.

For example, if you have a table containing customer information and another table containing order information, you can use the CROSS APPLY function to return only the customer information for those customers who have placed orders.

On the other hand, the OUTER APPLY function returns all the rows from the first table, whether or not there’s a matching row in the second table. If there’s no matching row in the second table, the result will still contain the row from the first table, but with NULL values in the columns from the second table.

Using the same example, if you use the OUTER APPLY function to join the customer information and order information tables, the result will contain all the customer information, even for customers who haven’t placed orders. In these cases, the columns from the order information table will contain NULL values.

Both CROSS APPLY and OUTER APPLY are important functions to understand as a beginner in SQL, as they allow you to join data from two different tables in a flexible and efficient manner.

In conclusion, CROSS APPLY and OUTER APPLY are powerful functions in SQL that allow you to join data from two tables. Understanding the differences between these two functions is important for any beginner in SQL or data analyst looking to effectively manage and extract insights from data. So, be sure to master these functions and add them to your SQL toolkit!

SQL for Beginners and Data Analyst – Chapter 28: cross apply, outer apply

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