CHARONLY()
 Determines the common denominator between two strings on the basis of
 individual characters
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 Syntax

     CHARONLY(<cString1>,<cString2>) --> cString

 Arguments

     <cString1>  Designates a sequence of characters that are not removed
     from <cString2>.

     <cString2>  Designates the string that is processed.

 Returns

     CHARONLY() returns the processed string <cString2>.

 Description

     CHARONLY() removes all characters from <cString2> that are not in
     <cString1>.  The function is particularly useful when comparing data
     that should have a standard format but has been input by different
     people.  This category can consist of things like telephone numbers,
     part numbers, customer numbers, etc. (see example).

 Example

     Since numbers are the only characters that are relevant in a telephone
     number, any characters that are not numbers are removed.  The result in
     each case is "2133907923":

     ? CHARONLY("0123456789", "213 - 39 07 923")
     ? CHARONLY("0123456789", "213 / 390 7923")