Real Rules to Qualify as Teradata Index
The Teradata RDBMS support five types of indexes
- Unique Primary Index (UPI)
- Unique Secondary Index (USI)
- Non-Unique Primary Index (NUPI)
- Non-Unique Secondary Index (NUPI)
- Join Index
The row hash is not the value, but a mathematically transformed address. The Teradata RDBMS uses this transformed address as a retrieval index.
The following rules apply to the indexes used in the Teradata Relation database:
- An index is a scheme used to distribute and retrieve rows of a data table. It can be based on the values in one or more columns of the table.
- A table can have a number of indexes, including one primary index, and up to 32 secondary indexes.
- An index for a relational table may be primary or secondary, and may be unique or non-unique. Each kind of index affects system performance, and can be important to data integrity.
- An index is usually defined on a table column whose values are frequently used in specifying WHERE constraints or join conditions.
- An index is used to enforce PRIMARY KEY and UNIQUE constraints.