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T-SQL / Stored Programming

Scalar UDF

Learn Scalar UDF in T-SQL through a focused explanation, a dedicated construct-specific example, an engineering boundary, and a mastery check.

10 min read • Intermediate

Scalar UDF is an atomic T-SQL topic inside Stored Programming. This lesson focuses on how the Scalar UDF construct is written, what it changes, and when it is the right tool.

Trace the example line by line. Identify the exact syntax for Scalar UDF, the input state before it runs, and the resulting value, control flow, database state, hardware behavior, or runtime effect afterward. Neighboring lessons use different constructs rather than renamed copies of this one.

Topic-specific example

tsql-05-05-scalar-udf.sql
tsql Try It Live 
SELECT dbo.Tax(total) AS tax FROM Orders;
Edge case / engineering note

For Scalar UDF, test the boundary that belongs to this exact feature rather than a generic failure case. Check invalid or empty input, NULL/unknown state, numeric limits, transaction or exception behavior, synthesis/runtime constraints, ownership/permission rules, or backtracking/control-flow effects where they apply.

Content source & attribution
Original Syntaxis Content · Original Syntaxis Content

Lesson quizzes

Scalar UDF Mastery Check →
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Inline table-valued function