Review the existing built-in functions

The second step in planning a UDX is to confirm that your function or aggregate is not already available as a built-in to SQL. Netezza Performance Server SQL offers a wide set of string, mathematical, analytical, and conversion functions. For example, if you want a function that changes the letter case of a string from uppercase to lowercase, or vice versa, Netezza Performance Server already provides built-in LOWER() and UPPER() functions for that conversion.

Also, never create a UDX that has the same name, but different letter-casing, as a built-in function. That is, do not create a UDX named upper() because the system has a built-in function UPPER(). Although it is possible to reuse an existing name by using delimited (quoted) identifiers, the practice often results in confusion for query users. It can also result in identifier collisions if the Netezza Performance Server administrator changes the default system casing to lowercase, for example. For a list of existing built-in functions and names, see the IBM® Netezza® Database User’s Guide.