Strange Performancetuning

IDS 9.4 (WE) on RH9 Linux 2.4.20 Hi all, we found a very strange Performance-Tuning of a simple SELECT-Statement, and now, we fear to have to rewrite a lot of application-code in order to tune our SQL-Statements: We have 3 tables (a,b,c), which are joined each by one join-column: a --> b --> c (each 1:n) All join-columns have a single index, some unique, some duplicate. We compared the following two SELECT's which have the same results. Query 1: SELECT a.* FROM a,b,c WHERE ... Query 2: SELECT b.join_col_to_a from b, c WHERE ... INTO TEMP temp01; CREATE INDEX idx01 ON temp01(join_col_to_a); UPDATE STATISTICS FOR TABLE temp01; SELECT a.* FROM a, temp01 WHERE ..... Query 1 takes 15 seconds Query 2 takes 1 second. (all 4 Statements!!) This is really confusing. We executed some UPDATE STAISTICS on these tables, and the optimizer seems to go the right way in both queries. However, Query1 is much more elegant and I expected, that Query1 should not be a problem for the Database-Server. I made the same test under IDS 9.21 and had (nearly) the same effect. Does anyone know the reason for this behaviour? Did I miss any important ONCONFIG-Setting? Thanks in advance! bye Markus