-
What is explain in teradata?
What is explain and how does it work?
Read Best Answer
Editorial / Best Answer
Madhulathamadduri- Member Since Jan-2010 | Apr 15th, 2011
The EXPLAIN modifier preceding an SQL statement generates an
English translation of the optimizer’s plan. It is fully parsed and
optimized, but not executed.
EXPLAIN returns:
Text showing how a statement will be processed (a plan).
An estimate of how many rows will be involved.
A relative cost of the request (in units of time).
This information is useful for:
• Predicting row counts.
• Predicting performance.
• Testing queries before production.
• Analyzing various approaches to a problem.
EXPLAIN may also be accessed using Teradata Visual Explain.senthang
- Jun 22nd, 2011
1. English version on optimizer plan2. to identify the objects used and kind of locks applied on those objects3. to identify the number of amp operation eg. single ot group amp4. to identify the data ...
yuvaevergreen
- Jun 6th, 2011
Explain statement generally gives the step by step analysis of the queries being executed in the database. It is the plan prepared by PE dispatched to the amps. It could also identify intermediate sp...
-
What is the purpose of Before Journal and After journal?
yuvaevergreen
- Jun 7th, 2011
Before Journal keeps the images of the table before making the change to the table. Very useful, if the changes need to be reverted incase of a fault or rollback. After Journal keeps the images of the table after the changes has been made to the table.
SanthuTeradata
- Mar 30th, 2011
We use both before journal and after journal in Permenent journal to do selective or full recovery of data..........consider Today Monday**Yesterday--------->Before ImageTuesday------------>Afte...
-
What is cliques? What is Vdisk and how it will communicate with physical data storage at the time of data retrieval through AMP ?
rajnsuccess
- Feb 6th, 2011
Clique is mainly used to prevent node failures.Group of nodes which share common disk drives is called CLIQUE.Group of cylindrical or physical disks arranged in array fashion is called VDISKS.After AM...
Sangra
- Feb 23rd, 2010
In case of one Disk failure the mirrored disk would provide the fallback protection In case of AMP failure the second AMP (in the fallback Clique) can provide the protection In case of Node failure th...
-
What is a common data source for the central enterprise data warehouse?
Operational data stores
-
EXCEPT and MINUS
What is the difference between EXCEPT and MINUS operator in Teradata SQL?
Abhilash AS
- Jan 11th, 2011
EXCEPT is ANSI Compliant and MINUS is Teradata specific. Function wise both are same.
-
Low and High Confidentiality
Explain What are Low and High Confidentiality in Explain command.
yuvaevergreen
- Aug 13th, 2010
The explain generally displays the plan which would be prepared by Optimizer. We can say that(though not accurate), plan would be the steps followed by Teradata to solve a query. Confidence levels ind...
samyukta.mogadali
- Jul 28th, 2010
Low Confidence: Normally when stats are difficult to use preciselyHigh Confidence: Normally Optimizer is sure of the results based on the stats available
-
SPOOL Process Error Types
How many types errors will be occur in total SPOOL process How will you connect a database server to other server?
developer_veni
- Jul 26th, 2009
We can connect from one server to another server in UNIX using the commandssh or FTP or SUssh -?ssh user_id@server_name
-
After creating tables dynamically in the Teardata, where is the GRANT table option usually done ? When tables are newly created, what is the default role and what the default privileges which get assigned ?
girishnayak
- Jun 27th, 2009
The default previleges being assigned to a creator are as belowRUDRSDGCGIXDPDTRFI
Neelima Dahi
- Aug 10th, 2007
The GRANT option for any particular table depends on the privilages of the user. If it is an admin user you can grant privilages at any point of time.The deafult roles associated with the newly created tables depend on he schema in which they are created.
-
Set and Multi Set Tables
What are set tables and multiset tables in Teradata?Explain with an appropriate example?
-
Teradata Optimization and Performance Tuning
What is optimization and performance tuning and How does it work in practical projects. Explain with an example.
asshu18
- Apr 14th, 2009
Optimization is the technique of selecting the least expensive plan (fastest plan) for the query to fetch results. Optimization is directly proportional to the availibility of --1. CPU resources 2. Sy...
-
How teradata makes sure that there are no duplicate rows being inserted when its a SET table?
Teradata will redirect the new inserted row as per its PI to the target AMP (on the basis of its row hash value), and if it find same row hash value in that AMP (hash synonyms) then it start comparing the whole row, and find out if duplicate.If its a duplicate it silently skips it without throwing any error.Cheers,Shilpa
saurabh.gupta4u
- Feb 6th, 2009
When the target table has UPI then the Row hash of PI column will lead to the AMP and the duplicate row is rejected with an error.In case of a NUPI defined on a SET table the duplicate row is compared on all columns and if the entire row is dups then it is rejected without an error code > 0.
-
How can we build data marts from FSLDM. is there any standard approach for this? Is FSLDM supports place holder for aggregated data?
gopi.mainframe
- Jul 26th, 2008
Here DM is a Subject oriented small data warehouse. It pics all the data from the HISTORICAL DATA WAREHOUSE IS OLAP.
-
-
-
-
Which two can be implemented as a centrally located logical architecture?
č operational data storeč logical data mart
Imad
- Aug 15th, 2006
1- Logical Data Mart Repository2- Provides a single version of the truth
-
-
What is the difference between start schma and Fsldm?
Rajendran77
- Feb 24th, 2006
FSLDM --> Financial Services Logical Data Model (FS-LDM). Its a Teradata standard product for Financial Sector (Specifically for Banks). It can be customized based on the user requirements.S...
rajendran
- Feb 24th, 2006
Hi there, FSLDM --> Financial Services Logical Data Model (Teradata FS-LDM 7.0) its developed by Teradata for the financial sectors (Speciafially for Bank). it can be customised based on the ...
Teradata Interview Questions
Read Best Answer
Ans