In B tree index single column indexes do not include entries for null values ; but bitmap and function based index can store all null entries .
Multi column indexes will store null values but only if at least one column is not null
1) If all columns contain null values , the entry will not be stored in the index
2) Adding a frequently null valued column to an index can impact performance by allowing the index to filter the nulls
3) If range scanning a column ie: < or > , put those columns at the end of the composite index
Multi column indexes will store null values but only if at least one column is not null
1) If all columns contain null values , the entry will not be stored in the index
2) Adding a frequently null valued column to an index can impact performance by allowing the index to filter the nulls
3) If range scanning a column ie: < or > , put those columns at the end of the composite index
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