SQL slow query patterns

1. given a composite index, make sure the order of your index is in line with your access pattern. you do not want the following

2. index for equality first then ranges so you limit the matching entries. you do not want the following

Search all employees of subsidiary ID = 27 who were born between 01-JAN-71 and 09-JAN-71

The right column order in multi-column indexes

Indexing SQL range conditions less than, greater than and between