Using CROSS APPLY and OUTER APPLY in SQL Server

Learn how to use CROSS APPLY and OUTER APPLY in SQL Server for advanced querying.

Introduction to CROSS APPLY and OUTER APPLY

CROSS APPLY and OUTER APPLY are used in SQL Server to join a table with a table-valued function.

They allow for more flexible queries compared to traditional JOINs.

Understanding these concepts can greatly enhance your SQL querying skills.

What is CROSS APPLY?

CROSS APPLY works like an INNER JOIN and returns only the rows from the left table that produce a result from the table-valued function.

What is OUTER APPLY?

OUTER APPLY works like a LEFT JOIN and returns all rows from the left table along with matched rows from the right table, filling in NULLs for non-matching rows.

When to Use CROSS APPLY vs OUTER APPLY?

Use CROSS APPLY when you only want rows that have matching data from the function.

Use OUTER APPLY when you want all rows from the left table regardless of matches.

Quick Checklist

Understand the difference between CROSS APPLY and OUTER APPLY
Know when to use each apply type
Practice with table-valued functions

FAQ

What is the main difference between CROSS APPLY and INNER JOIN?

CROSS APPLY is specifically for table-valued functions, while INNER JOIN is used for standard table joins.

Can OUTER APPLY return NULL values?

Yes, OUTER APPLY returns NULL for non-matching rows from the right table.

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