Concatenation problem select field1 || field2 ok in SQL but how in 4gl ?

This code is fine is SQL "select field1 || field2 as field1and2 ok in SQL but how in 4gl ? I am trying to overcome a problem where the table has a multi-part index on the 1st 2 fields (I cannot change this) and keep on getting the error " 245: Could not position within a file via an index. 103: ISAM error: illegal key descriptor (too many parts or too long).Derek Ruskin