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Contents
- 1 Teradata Tutorial – Secondary Index, data access using SI , etc
- 2 What is the Teradata non-unique secondary index?
- 3 Can a Teradata table contain more than one index?
- 4 What is the difference between Teradata USI and Nusi?
- 5 What are non-unique secondary indexes (NuSI)?
- 6 Information related to the topic non unique secondary index in teradata
Teradata Tutorial – Secondary Index, data access using SI , etc
What is the Teradata non-unique secondary index?
The Teradata Non-Unique Secondary Index ( NUSI) is an alternative data access path that can reduce IOs. While B+ Tree Indexes are a quite commonly used index mechanism in relational database systems, Teradata uses a different approach based on hashing.
Can a Teradata table contain more than one index?
A table can contain only one primary index. More often, you will come across scenarios where the table contains other columns, using which the data is frequently accessed. Teradata will perform full table scan for those queries. Secondary indexes resolve this issue.
What is the difference between Teradata USI and Nusi?
Teradata distinguishes between unique secondary indexes (USI) and non-unique secondary indexes (NUSI). Although the naming may seduce to assume they are technically the same, they are not at all. This article is related to the non-unique Teradata secondary index or NUSI.
What are non-unique secondary indexes (NuSI)?
Non-unique secondary indexes are sub-tables; they do not show up as real objects in the DBC data dictionary tables (in contrast to Join Indexes). NUSI rows are not hash distributed.
What is a non-unique secondary index (NuSI)?
A Non-Unique Secondary Index (NUSI) is designed to prevent the full table scan (FTS) and usually contains duplicate values. Once you create a secondary index, a subtable is created on each AMP. The main difference between the USI and NUSI is that USI subtable rows are hashed and the NUSI subtable rows are AMP-Local.
What is a unique secondary index (USI)?
A Unique Secondary Index allows only unique values for the columns defined as USI. Accessing the row by USI is a two amp operation. The following example creates USI on EmployeeNo column of employee table.
What are the different types of secondary indexes?
Unique Secondary Indexes Nonunique Secondary Indexes Multiple NUSI Access NUSI Bit Mapping NUSIs and Query Covering Value-Ordered NUSIs and Range Conditions Selecting a Secondary Index Secondary Index Access Summarized by Example
What is the difference between B+ tree indexes and Nusi?
While B+ Tree Indexes are a quite commonly used index mechanism in relational database systems, Teradata uses a different approach based on hashing. Teradata distinguishes between unique secondary indexes (USI) and non-unique secondary indexes (NUSI). Although the naming may seduce to assume they are technically the same, they are not at all.
References:
The Teradata NUSI Or Nonunique Secondary Index
Teradata – Secondary Index – tutorialspoint.com
Teradata Secondary Indexes – javatpoint
How to Create or Drop the Secondary Index in Teradata
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Questions just answered:
What is the difference between Teradata USI and Nusi?
What is the Teradata non-unique secondary index?
Can a Teradata table contain more than one index?
What is a non-unique secondary index (NuSI)?
What is a unique secondary index (USI)?
What are the different types of secondary indexes?
What is the difference between B+ tree indexes and Nusi?
What are non-unique secondary indexes (NuSI)?
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