Here are some of the most frequently asked Teradata interview questions and answers to help you succeed in your next interview.
1. Speaking of Teradata, what are the basic differences between fast load and multiload?
So far as fast load is concerned, it is essentially meant to load colossal amounts of data through the use of multiple sessions. On the other hand, multiload is chiefly used for the maintenance of tables and views. The striking feature of the same is that it also works with non-empty tables.
2. Since you mentioned sessions, how can you determine the number of sessions?
There are several factors to the same. Firstly, you need to gauge the Teradata performance and workload before gauging the client type and the corresponding performance and workload. Then, channel performance and network topology are major determinants of the number of sessions. Lastly, you need to evaluate the volume of the data to be processed by the concerned application.
3. Against the backdrop of performing sessions, what do you understand by inner join and outer join?
An inner join is one which primarily retrieves data from both tables where the data is chiefly specified. An outer join, on the other hand, chiefly gets data from the source table and gauges the necessary criteria in order to return the data.
4. What do you understand by the term collect statistics?
Basically speaking, the collect statistics feature is chiefly used to gather demographic data for one more column of a table. Having done that, it stores the gathered constituents in the data dictionary. Consequently, the stored data is then used by the optimizer in accordance with the concerned requirements.
5. Can you describe the significance of data mart?
A data mart may be defined as a subset of data to be used for a specified purpose. Specifically speaking, data marts may be conceptually likened to data repositories in order to be hauled up for use as per requirements. Essentially, data marts are chiefly identified as being independent and logical extensions of data. They may be oriented to the momentary coordinates of a specific community of users as per the needs.
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6. What do you understand by the term spool space?
A spool space may be defined as something chiefly sued to contain rows for during processing in the answer set of a particular transaction. Also, there is a definitive condition for reaching the maximum spool space. Generally speaking, you need to optimize the query appropriately. In order to limit the particular answer set, you must use appropriate conditions in the WHERE clause of the concerned query.
7. What is the chief purpose of the SLEEP command in fast load in Teradata?
The SLEEP command is essentially meant to specify the number of minutes to wait before logging in order to establish or reestablish all the sessions. In fact, the command may be used with all other loads, apart from the fast load. Generally speaking, the need for inducing a sleep command arises specifically when all the loader slots are used or sessions are not immediately available.
8. What do you understand by the term sparse index?
A sparse index may be defined as a kind of Join index which consists of a WHERE clause which trims the number of redundant indices in the concerned rows. As the name itself amply implies, the sparse index is chiefly used to reduce redundancy as much as possible.
9. What is a slowly changing dimension?
Essentially, a slowly changing dimension is nothing less than an aberration. Definitively, it is the evidence of a potential variation of an attribute. Accordingly, there are several ways to get rid of the problem. The basic way is to tamper with the existing records in order to induce replacement and insertion of a new record.
10. What is online transaction processing?
Online transaction processing is chiefly defined as the process of recording large amounts of data and storing them in as little space as possible. Accordingly, online transaction processing may be used for multiple functions such as daily transactions and intricate business affairs.
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