Top 20 Teradata Dba Interview Questions You Must Prepare 02.Mar.2024

FALLBACK requests that a second copy of each row inserted into a table be stored on another AMP in the same cluster. This is done when AMP goes down or disk fails.

  • It allows us to write SQL statements along with BTEQ commands. We can use BTEQ for importing, exporting and reporting purposes.
  • The commands start with a (.) dot and can be terminated by using (;), it is not mandatory to use (;).
  • BTEQ will assume any thing written with out a dot as a SQL statement and requires a (;) to terminate it.

No, because they become a single amp operation and my company didn’t encourage that.

The three-tier differs from the two-tier architecture by strictly enforcing a logical separation of the graphical user interface, business logic, and data. The three-tier is widely used for data warehousing today. Organizations that require greater performance and scalability, the three-tier architecture may be more appropriate. In this architecture, data extracted from legacy systems is cleansed, transformed, and stored in high –speed database servers, which are used as the target database for front-end data access.

A data mart is a special purpose subset of enterprise data used by a particular department, function or application. Data marts may have both summary and details data, however, usually the data has been pre aggregated or transformed in some way to better handle the particular type of requests of a specific user community. Data marts are categorized as independent, logical and dependant data marts.

An operational data store (ODS) is primarily a “dump” of relevant information from a very small number of systems (often just one) usually with little or no transformation. The benefits are an ad hoc query database, which does not affect the operation of systems required to run the business. ODS’s usually deal with data “raw” and “current” and can answer a limited set of queries as a result.

The difference between real time and near real time can be summed up in one word: latency. Latency is the time lag that is between an activity completion and the completed activity data being available in the data warehouse. In real time, the latency is negligible whereas in near real time the latency is a tangible time frame such as two hours.

If the teradata is going to be only a data base means It won’t change the System development life cycle (SDLC).

If you are going to use the teradata utilities then it will change the Architecture or SDLC.

If your schema is going to be in 3NF then there won’t be huge in change.

  • Teradata performance and workload.
  • Client platform type, performance and workload.
  • Channel performance for channel attached systems.
  • Network topology and performance for network attached systems.
  • Volume of data to be processed by the application.

CASE value_expression_1 WHEN value_expression_n THEN scalar_expression_n


Sub string is used with char fields. So it cannot be used. To extract month from a date column, ex select extract (month from ). Same thing for year or day. Or hour or minutes if it’s a time stamp (select extract (minute from column name).

  • Real-time data warehousing is a combination of two things:
  • real-time activity and
  • data warehousing.
  • Real-time activity is activity that is happening right now. The activity could be anything such as the sale of widgets. Once the activity is complete, there is data about it. Data warehousing captures business activity data. Real-time data warehousing captures business activity data as it occurs. As soon as the business activity is complete and there is data about it, the completed activity data flows into the data warehouse and becomes available instantly. In other words, real-time data warehousing is a framework for deriving information from data as the data becomes available.

Analyzing of large volumes of relatively simple data to extract important trends and new, higher level information. For example, a data-mining program might analyze millions of product orders to determine trends among top-spending customers, such as their likelihood to purchase again, or their likelihood to switch to a different vendor. 

OLTP stands for Online Transaction Processing. OLTP uses normalized tables to quickly record large amounts of transactions while making sure that these updates of data occur in as few places as possible. Consequently OLTP database are designed for recording the daily operations and transactions of a business. E.g. a timecard system that supports a large production environment must record successfully a large number of updates during critical periods like lunch hour, breaks, startup and close of work.

Data in a Database is Detailed or Transactional, Both Readable and Write able and current.

Data in data warehouse is detailed and summarized, storage place for historical data.

Group by those fields and select id, count(*) from table group by id having count (*) > 1.

Just like channel driver, Teradata Gateway acts as a medium of communication between the Parse Engine and applications that are attached to network clients. Only one Gateway is assigned per node.

  • Get business requirements.
  • Create High Level Conceptual Data Model.
  • Create Logical Data Model.
  • Select target DBMS where data-modeling tool creates the physical schema.
  • Create standard abbreviation document according to business standard.