Noconcatenate is, indeed, the answer, but I doubt if it can be appended directly to the SQL statement. It can, however, be added to the preceding LOAD statement in front of the SQL SELECT:
SQL select * from searchengine1.system;
SQL select * from searchengine2.system;
If the two tables have the same field names then QlikView will try to join the tables on ALL of the fields.
(be careful of synthetic keys too )
Few of ways of fixing this are:
1. Use Noconcatenate keyword or
2.Rename the fields in one table or
3.Use QUALIFY keyword to prefix the fields in your tables with the table name.