SQL Server series: Custom functions

A user-defined function can be called as a system function in a query or stored procedure, can accept parameters, perform operations, and return the result of the operation as a value. The return value can be a single scalar or result set.

1. Scalar functions

Scalar functions return a scalar value that determines the type, for scalar functions of multiple statements, the function body defined in the begin End block contains a series of T-SQL statements that return a single value.

2. Table-Valued functions

A table-valued function is a function that returns a data type table, and the returned table value is the result of a single SELECT statement query.

SQL Server series: Custom functions