Function calls

note

This article is about function calls as part of the SQL syntax that USoft supports.

Function calls

Column expressions may contain functions calls. A function call is signalled by the required presence of parentheses around the column name or literal. The function name is the name immediately preceding the opening parenthesis:

*function-name*( { *column* | *literal* } [ , *argument* ... ] )

Functions expect 0, 1 or multiple arguments, which may be required or optional depending on the function. Function arguments are separated by commas. Functions may be nested.

Example

In this example, the UPPER( ) function converts retrieved values from the NAME column to all-uppercase. The result is passed as the first argument of the SUBSTR( ) function, which in this case takes 2 arguments, the input string and the number 5, which causes it to return the input string from position 5 onward.

SELECT     SUBSTRING( UPPER( name ), 5 )

This example returns the string SON if the retrieved name is Johnson.

Method invocations

Invocations of methods of RDMI components are a special case of function call. These invocations are signalled by the presence of a full-stop separator ( . ) in the function name:

*component.method*( { *column* | *literal* } )

These invocations can alternatively be expressed by an INVOKE ... WITH SELECT statement.