|#Highlights Of Teradata Indexes:|
- Unique Primary Index (UPI)
- Unique Secondary Index (USI)
- Non-Unique Primary Index (NUPI)
- Non-Unique Secondary Index (NUPI)
- Join Index
The typical index contains two fields: a value and a pointer to instances of that value in a data table. Because the Teradata RDBMS uses hashing to distribute rows across the AMPs, the value is condensed into an entity called a row hash, which is used as the pointer. 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.
Read more : Teradata+Indexes