Jeffrey, And index is a B(Binary)+ tree, the plus means that it auto adjusts and balances itself as it builds or shrinks.
After UniData 5.2 UniQuery will use as many indices as it can. In your case it is the equivalent of doing two UniQuery selects to two different lists and then doing a MERGE.LIST. If you are always wanting a combined index lookup on those two values you can create an I-Descriptor that combines them and index the I-Descriptor. Then use the I-Descriptor in your select statements. Remember using an Index doesn't always mean faster selects. If your index brings back a lot of records then you are processing them by index pointer and the disk reads will be all over the file. Whereas without the index you are reading the file going through it by groups and it will minimize the disk reads. David A. Green (480) 201-7953 DAG Consulting -----Original Message----- From: u2-users-boun...@listserver.u2ug.org [mailto:u2-users-boun...@listserver.u2ug.org] On Behalf Of jeffrey Butera Sent: Friday, December 06, 2013 8:09 AM To: U2 Users List Subject: [U2] Unidata index/query ? Unidata 7.3.3 on RedHat: I have a table with numerous indicies built: File.................. H08.CR.COURSE.EVALS Alternate key length.. 20 Node/Block size....... 4K OV blocks............. 1 (0 in use, 0 overflowed) Indices............... 6 (6 D-type) Index updates......... Enabled, No updates pending Index-Name...... F-type K-type Built Empties Dups In-DICT S/M F-no/VF-expr.... XCCE.STUDENT.ID D Num Yes Yes Yes Yes S 8 XCCE.STATUS D Txt Yes No Yes Yes S 17 XCCE.COURSE.NAME D Txt Yes No Yes Yes S 14 XCCE.TERM D Txt Yes No Yes Yes S 12 XCCE.TYPE D Txt Yes No Yes Yes S 22 XCCE.SUBJECT D Txt Yes No Yes Yes S 23 Since these are data fields (nothing computed on-the-fly) and indexed, queries should be fast. The table has approximately 737,000 records. This query runs in under 1 second: SELECT H08.CR.COURSE.EVALS WITH XCCE.TERM EQ '2013F' However this query takes 10+ seconds (or longer) - even with two indexed fields: SELECT H08.CR.COURSE.EVALS WITH XCCE.TERM EQ '2013F' AND XCCE.TYPE EQ 'FINCRSE' I'm at a loss to explain the second, any insight appreciated. -- Jeffrey Butera, PhD Associate Director for Application and Web Services Information Technology Hampshire College 413-559-5556 _______________________________________________ U2-Users mailing list U2-Users@listserver.u2ug.org http://listserver.u2ug.org/mailman/listinfo/u2-users _______________________________________________ U2-Users mailing list U2-Users@listserver.u2ug.org http://listserver.u2ug.org/mailman/listinfo/u2-users