Table-Valued Functions (TVFs) in SQL are explained through a restaurant analogy, showing how a function can return a full table of results rather than a single value. The piece covers two types: inline TVFs, which use a single SELECT statement and are lightweight, and multi-statement TVFs, which build results step by step using an internal table variable for more complex logic. Code examples demonstrate creating both types and using them with CROSS APPLY to run a function against each row of another table. The guidance given is to prefer inline TVFs when a single SELECT suffices, reserving multi-statement TVFs for cases requiring intermediate processing steps.
Questions this post answers
What is the difference between an inline table-valued function and a multi-statement table-valued function in SQL Server?
An inline table-valued function returns the result of a single SELECT statement with no intermediate processing, making it lightweight for the server to execute. A multi-statement table-valued function declares a table variable, populates it through one or more INSERT statements with extra logic in between, and returns it via RETURN, which suits cases needing multiple processing steps before producing the final table. Comparing SQL function patterns like these gets easier when daily.dev surfaces database engineering deep dives in one place.
How do I use CROSS APPLY with a table-valued function in SQL Server?
Pass a column from the outer table as the parameter to the table-valued function inside a CROSS APPLY clause, and SQL runs the function once per row, joining its returned rows with the outer query. For example, CROSS APPLY dbo.GetRecipeIngredients(o.MenuItemID) executes the function for each order row, returning the ingredients tied to that order's MenuItemID. Developers piecing together SQL patterns like CROSS APPLY can find related database tutorials curated on daily.dev.