Select/Omit Criteria specifies details of any records that are to be either selected or omitted from an index.
Select/Omit
Select/Omit And/Or
Select/Omit Type
Select/Omit Column Name
S/O Operator
S/O Value
S/O Range
Also See
3.4 Indexes
3.4.9 Index Keys
Select Omit Concepts in the Developer Guide.