.svg)
Acmeware Achieves 100% Submission Success
Featured article
Acmeware completes 100% successful submissions for eCQM, PQRS, Hospital IQR, and Joint Commission ORYX using OneView for acute and ambulatory settings.
TL/DR
SQL Server user-defined functions save time by encapsulating reusable logic into database objects. Two types serve different needs.
- Scalar functions return a single value, ideal for calculations like patient age from date of birth
- Table-valued functions return multiple rows, useful for computing all time components (years through minutes) between two dates
- Part 2 covers additional advantages, best practices, and the DRY principle for function design
User-defined functions in SQL Server let you create reusable logic for common calculations like patient age and clinical time intervals.
Article content
A function is a SQL query saved as a database object, which leverages and outputs data to serve a focused purpose. Once created, functions streamline data production and allow technology to simplify workflows.
Scalar Functions
Scalar functions return a single value when called. To illustrate, consider an age-calculation example using a function named fnAgeYears.
The function demonstrates how to calculate a patient's age in years based on their date of birth and a specified date of interest (such as admission or lab test dates). The implementation includes a CASE statement that accounts for specific day-of-year calculations and accommodates leap year birthdays on February 29.
Use case: When combining patient data from multiple sources where only date of birth is available, or when reporting requires historical age at specific timepoints.
Table-Valued Functions
Table-valued functions (TVFs) differ fundamentally. They return multiple values each time they are called, including multiple rows of values, just like a table.
Consider tvAw_AgeAll as an example TVF that calculates all discrete time components (years through minutes) from two datetime values. Users can SELECT from it like a standard table, retrieving whichever time intervals suit their clinical calculations.
Advantage: One generic function serves multiple reporting needs without code duplication.
User-defined functions offer flexibility and coding efficiency. In Part 2, we cover additional advantages and best practices.
.svg){kind=icon}
