What if you need an index other than a primary index? You can only have one primary index on a table, but what if you have a requirement to have multiple indexes on a table? Teradata gives you the secondary index (SI) to satisfy that requirement. You can use a primary index for distribution and access, but to have a secondary access path, you can use SI:
CREATE UNIQUE INDEX (Coulumn_Name) on TABLE_NAME; -- UNIQUE INDEX, USI CREATE INDEX (Coulumn_Name) on TABLE_NAME; -- NON UNIQUE INDEX, NUSI
Secondary indexes supply alternate access paths. As we know, primary indexes are used for the distribution of rows, and sometimes, to reduce the skewness of tables, we might need to choose columns based on even distribution instead of selectivity. So, to rescue and provide the alternative approach, Teradata has a feature known as the secondary index.
This increases performance. For best results, base secondary indexes on frequently used set selections and...