When you call a UDF in the body of a tag that has a query attribute, such as a cfloop query=... tag, any function argument that is a query column name passes a single element of the column, not the entire column. Therefore, the function must manipulate a single query element.

For example, the following code defines a function to combine a single first name and last name to make a full name. It queries the cfdocexamples database to get the first and last names of all employees, and then it uses a cfoutput tag to loop through the query and call the function on each row in the query.

<cfscript>
function FullName(aFirstName, aLastName)
 { return aFirstName & " " & aLastName; }
</cfscript>

<cfquery name="GetEmployees" datasource="cfdocexamples"> 
    SELECT FirstName, LastName
    FROM Employee
</cfquery>

<cfoutput query="GetEmployees">
#FullName(FirstName, LastName)#<br>
</cfoutput>

You generally use functions that manipulate many rows of a query outside tags that loop over queries. Pass the query to the function and loop over it inside the function. For example, the following function changes text in a query column to uppercase. It takes a query name as an argument.

function UCaseColumn(myquery, colName) {
    var currentRow = 1;
    for (; currentRow lte myquery.RecordCount; currentRow = currentRow + 1)
    {
        myquery[colName][currentRow] = UCase(myquery[colName][currentRow]);
    }
    Return "";
}

The following code uses a script that calls the UCaseColumn function to convert all the last names in the GetEmployees query to uppercase. It then uses cfoutput to loop over the query and display the contents of the column.

<cfscript>
    UCaseColumn(GetEmployees, "LastName");
</cfscript>
<cfoutput query="GetEmployees">
    #LastName#<br>
</cfoutput>