Chuyển tới nội dung
Trang chủ » Non Unique Secondary Index In Teradata? The 30 Detailed Answer

Non Unique Secondary Index In Teradata? The 30 Detailed Answer

Are you looking for an answer to the topic “non unique secondary index in teradata“? We answer all your questions at the website vi-magento.com in category: https://vi-magento.com/chia-se/. You will find the answer right below.

Non-Unique Secondary Index (NUSI). As soon as you define secondary index, the next move comes from Teradata creating a Subtable on every AMP. This is true for both the USI and the NUSI. Subtables require additional disk space and maintenance; they should be only used on queries that run again and again.

Teradata Tutorial – Secondary Index, data access using SI , etc

Teradata Tutorial – Secondary Index, data access using SI , etc
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.

The Technical Details of the Nonunique Secondary Index in Teradata – NUSI Like any index of a relational database system, the Teradata NUSI provides an alternative access path to the rows of a table. Indexes serve to keep the resource consumption (especially IOs) as low as possible.

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.

The main difference between the USI and NUSI is that USI subtable rows are hashed and the NUSI subtable rows are AMP-Local. But why NUSI is AMP Local and what does it mean? It is obvious that NUSI value is duplicate and there could be huge number of duplicate values in it. So Teradata takes a different strategy to maintain subtable in this case.

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.

Non-Unique Secondary Index (NUSI) A Non-Unique Secondary Index (NUSI) allows duplicate values for the columns defined as NUSI. A Non-Unique Secondary Index is usually specified to prevent full-table scans, in which every row of a table is read.

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

Information related to the topic non unique secondary index in teradata

Here are the search results of the thread non unique secondary index in teradata from Bing. You can read more if you want.


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)?

non unique secondary index in teradata

You have just come across an article on the topic non unique secondary index in teradata. If you found this article useful, please share it. Thank you very much.

Trả lời

Email của bạn sẽ không được hiển thị công khai. Các trường bắt buộc được đánh dấu *