Teradata Interview Questions and answersQuestion.1What is the difference between FastLoad and MultiLoad?Answer:FastLoad uses multiple sessions to quickly load large amount of data on empty table. MultiLoad is used for high-volume maintenance on tables and views. It works with non-empty tables also. Maximum 5 tables can be used in MultiLoad.

Question.2Which is faster?Answer:FastLoad.

Question.3Difference between Inner join and outer join?Answer:An inner join gets data from both tables where the specified data exists in both tables.

An outer join gets data from the source table at all times, and returns data from the outer joined table ONLY if it matches the criteria.[sociallocker]

Question.4What is multi Insert?Answer:Inserting data records into the table using multiple insert statements. Putting a semi colon in front of the key word INSERT in the next statement rather than terminating the first statement with a semi colon achieves it.

Insert into Sales select * from customer

Insert into Loan select * from customer;

Question.5Is multi insert ANSI standard?Answer:No.

Question.6How do you create a table with an existing structure of another table with data and with no data?Answer:Create table Customer dummy as Customer with data / with no data;

Question.7What is the opening step in Basic Teradata Query script?Answer:Logon tdipid/username, password.

Question.8You are calling a Bteq script, which drops a table and creates a table. It will throw an error if the table does not exist. How can you do it without throwing the error?Answer:You can it by setting error level to zero before dropping and resetting the error level to 8 after dropping.

Question.9ERRORLEVEL (3807)Answer:SEVERITY 8;

Question.10Can you FastExport a field, which is primary key by putting equality on that key?Answer:No.

Question.11Did you write stored procedures in Teradata?Answer:No, because they become a single amp operation and my company didnt encourage that.

Question.12What is the use of having indexs on table?Answer:For faster record search.

Question.13Did you use Query man or SQL assistance?Answer:SQL assistant 6.1

Question.14.I am updating a table in Bteq. It has to update a large number of rows, so its really slow. What do you suggest?Answer:In Teradata it is not recommended to update more than 1 million rows due to journal space problems, if it is less than that and its slow in the Bteq, you might want to add collect statistics statement before the update statement.

Question.15 Is it necessary to add? QUIT statement after a Bteq query when I am calling it in a Unix environment?Answer:Not necessary but it is good to add a QUIT statement after a query.

Question.16There is a column with date in it. If I want to get just month how It can be done? Can I use sub string?Answer: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 its a time stamp (select extract (minute from column name).

Question.17Whats the syntax of sub string?Answer:SUBSTRING (string_expression, n1 [n2])

Question.18Did you use CASE WHEN statement. Can you tell us a little about it?Answer:Yes. When a case has to be selected depending upon the value of the expression.

Question.19While creating table my DBA has FALLBACK or NO FALLBACK in his DDL. What is that?Answer: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.[/sociallocker]Informatica ETL Interview Questions and Answers

Question.1Can you use mapping without source qualifier?Answer:Not possible, If source RDEMS/DBMS/Flat file use SQ or use normalizer if the source cobol feed.

Question 2.When do you use a normalizer?Answer: Normalized can be used in Relational to denormilize data. [sociallocker]

Question.3What are stored procedure transformations. Purpose of sp trar sformation. How did you go about using your project?Answer:Connected and unconnected stored procedure.

Unconnected stored procedure used for data base level activities such as pre and post load Connected stored procedure used in informatica level for example passing one parameter as input and capturing return value from the stored procedure.

Normal row wise check

Pre-Load Source (Capture source incremental data for incremental aggregation)

Post-Load Source (Delete Temporary tables)

Pre-Load Target (Check dick space available)

Post-Load Target (Drop and recreate index)

Question.4What is lookup and difference between Types of lookup. What exactly happens when a lookup is cached. How does a dynamic: lookup cache work.Answer:Lookup transformation used for check values in the source and target tables(primary key values). There are 2 type connected and unconnected transformation

Connected lookup returns multiple values if condition true Where as unconnected return a single values through return port.

Connected lookup return default user value if the condition does not mach Where as unconnected return null values Lookup cache does: Read the source/target table and stored in the lookup cache .

Question.5How did you schedule sessions in your project?Answer: Run once (set 2 parameter date and time when session should start) Run Every (Informatica server run session at regular interval as we configured, parameter Days, hour, minutes, end on, end after, forever)

Customized repeat (Repeat every 2 days, daily frequency hr, min, every week, every month) Run only on demand(Manually run) this not session scheduling.

Question.6Explain lookup cache, various caches?Answer: Lookup transformation used for check values in the source and target tables(primary key values). Various Caches:

Persistent cache (we can save the lookup cache files and reuse them the next time process the lookup transformation)

Re-cache from database (if the persistent cache not synchronized with lookup table you can- configure the lookup transformation to rebuild the lookup cache)

Static cache (When the lookup condition is true, Informatica server return a value from lookup cache and its does not update the cache while it processes the lookup transformation)

Dynamic cache (Informatica server dynamically inserts new rows or update existing rows in the cache and the target. Suppose if we want lookup a target table we can use dynamic cache)

Shared cache (we can share lookup transformation between multiple transformations in a mapping.2 lookup in a mapping can share single lookup cache) .

Question.7Which path will the cache be created?Answer: User specified directory. If we say c:\ all the cache files created in this directory.

Question.8where do you specify all the parameters for lookup caches?Answer: Lookup property sheet/tab.

Question.9How do you remove the cache files after the transformation?Answer:After session complete, DTM remove cache memory and deletes caches files. In case using persistent cache and Incremental aggregation then caches files will be saved.

Question.10What is the use of aggregator transformation?Answer: To perform Aggregate calculation Use conditional clause to filter data in the expression Sum(commission, Commission >2000) Use non-aggregate function if (max(quantity) > 0, Max(quantity), 0))

Question.11What are the contents of index and cache files?Answer: Index caches files hold unique group values as determined by group by port in _the transformation. Data caches files hold row data until it performs necessary calculation.

Question.12How do you call a store procedure within a transformation?Answer: In the expression transformation create new out port in the expression write: sp. stored procedure name (arguments).

Question.13Is there any performance issue in connected & unconnected lookup? If yes, How?Answer: Yes Unconnected lookup much more faster than connected lookup why because in unconnected not connected to fly other transformation we are calling it from other transformation so it minimize lookup cache value Where as connected transformation connected to other transformation so it keeps values in the lookup cache.

Question.14What is dynamic lookup?Answer: When we use target lookup table, Informatica server dynamically insert new values or it updates if the values exist and passes to target table.

Question. 15How lnfcrmatica read data if source have one relational and flat file?Answer:Use joiner transformation after source qualifier before other transformation.

Question.16How you will load unique record into target flat file from source f13t files has duplicate data?Answer: There are 2 we can de this either we can use R. ink transformation or oracle external table in rank transformation using group by port (Group it e records) and then set no. of rank 1. Rank transformation return one value from the group. That the values wit De a unique one.

Question.17Can you use flat file for repository?Answer: No, We cant

Question.18Without Source Qualifier and joiner how will you join tables?Answer:Yr -IPA% In session level we have option user defined join. Where we can write join condition.

Question.19Update strategy set DD_Update but in session level have insert. What will happens?Answer: Insert take place. Because this option override the mapping level option . [/sociallocker]Informatica Interview Questions with answers

Question.1What are the different uses of a repository manager?Answer:Repository manager used to create repository which contains metadata the informatca uses to transform data to from source to target. And also it use to create inforrnatica users and folders and copy, backup and restore tie repository .

Question.2How do you take care of security using a repository manager?Answer:Using repository privileges, folder permission and locking. Repository privileges(Session operator. Use designer, Browse repository, Create session and batches, Administer repository, administer server, super user) Folder permission(owner, groups, users) . Locking(Read, Write, Execute, Fetch, Save) .[sociallocker]

Question.3What is a folder?Answer:Folder contains repository objects such as sources, targets, mappings, transformation which are helps logically, organize our data warehouse.

Question.4Can you create a folder within designer?Answer:Not possible

Question.5What are shortcuts? Where it can tie used? What are the advantages?Answer:There are two shortcuts (Local and global) Local used in local repository and global used in global repository. The advantage is reusing an object without creating multiple objects. Say for example a source definition want to use in 10 mappings in 10 different folders without creating 10 multiple source you create 10 shortcuts.

Question.6how do you increase the performance of mappings?Answer:Use single pass read(use one source qualifier instead of multiple SO for same table) Minimize data type conversion (Integer to Decimal again back to Integer) Optimize transformation(when you use Lookup, aggregator, filter, rank and joiner).

Use caches for lookup Aggregator use presorted port, increase cache size, minimize input/out port as much as possible Use Filter wherever possible to avoid unnecessary data flow.

Question.7Explain lnformatica Architecture?Answer:Informatica consist of client and server. Client tools such as Repository -manager, Designer, Server manager. Repository data base contains metadata it read by inforrnatica server used read data from source, transforming and loading into target.

Question.8What are the constants used in update strategy?Answer:OD_INSERT, DD_UPDATE, DD_DELETE, DD REJECT.

Question.9what is difference between connected and unconnected lookup transformation?Answer:Connected lookup return multiple values to other transformation Where as unconnected lookup return one values If lookup condition matches Connected lookup return user defined default values Where as unconnected lookup return null values Connected supports dynamic caches where as unconnected supports static.

Question.10What you will do in session level for update strategy transformation?Answer:In session property sheet set Treat rows as Data Driven .

Question.11What are the port available for update strategy , sequence generator, Lookup, stored procedure transformation?Answer:Transformations Port

Update strategy Input, Output

Sequence Generator Output only

Lookup Input, Output, Lookup, Return

Stored Procedure Input, Output

Question.12what is an active and passive transformation?Answer:Active transformation change the no. of records when passing to targe(example filter) where as passive transformation will not change the transformation(example expression) .

Question.13What are the tracing level?Answer:Normal It contains only session initialization details and transformation details no. records rejected, applied

Terse Only initialization details will be there Verbose Initialization Normal setting information plus detailed information about the transformation.

Verbcse data Verbose in it. Settings and all information about the session .

Question.14How will you make records in groups?Answer: Using group by port in aggregator .

Question.15Need to store value like 145 into target when you use aggregator, how will you do that?Answer:Use Round() function

Question.16How will you move mappings from development to production database?Answer:Copy all the mapping from development repository and paste production repository while paste it will prompt whether you want replace/rename. If say replace informatica replace all the source tables with repository database.

Question.17What is difference between aggregator and expression?Answer:Aggregator is active transformation and expression is passive transformation Aggregator transformation used to perform aggregate calculation on group of records really Where as expression used perform calculation with single record.

Question.18What are Router transformation?Answer:Router transformation is an Active and Connected transformation. It is similar to filter transformation. The only difference is, filter transformation drops the data that do not meet the condition whereas router has an option to capture the data that do not meet the condition. It is useful to test multiple conditions.

Question.19What are Sorter transformation?Answer:Sorter transformation is a Connected and an Active transformation. It allows to sort data either in ascending or descending order according to a specified field.[/sociallocker]

Informatica Interview Questions experienced

Question.1How to Join 2 tables connected to a Source Qualifier w/o having any relationship defined .Answer: By writing an sql override.

Question.2In a mapping if three are 2 targets to load header and detail, how to ensure that header loads first then detail table.Answer: Constraint Based Loading (if no relationship at oracle level) OR Target Load Plan (if only 1 source qualifier for other tables) OR select first the header target table and then the detail table while dragging them in mapping.[sociallocker]

Question.3A mapping just take 10 seconds to run, it takes a source file and insert into target, but before that there is a Stored Procedure transformation which takes around 5 minutes to run and gives output Y or N. If Y then continue feed or else stop the feed. (Hint: since SP transformation takes more time compared to the mapping, it shouldnt run row wise).Answer: There is an option to run the stored procedure before starting to load the rows.

Question.4What is difference between view and materialized view?Answer:Views contains query whenever execute views it has read from base table Where as M views loading or replicated takes place only once, which gives you better query performance .refresh m views 1.on commit and 2. on demand (Complete, never, fast, force) .

Question.5What is bitmap index why its used for DWH?Answer: bitmap for each key value replaces a list of rowids. Bitmap index more efficient for data warehousing because low cardinality, low updates, very efficient for where class

Question.6What is star schema? And what is snowflake schema?Answer:The center of the star consists of a large fact table and the points of the star are the dimension tables. snowflake schemas normalized dimension tables to eliminate redundancy. That is, the Dimension data has been grouped into multiple tables instead of one large table.

Star schema contains demoralized dimension tables and fact table, each primary key values in dimension table associated with foreign key of fact tables.

Here a fact table contains all business measures (normally numeric data) and foreign key values, and dimension tables has details about the subject area. Snowflake schema basically a normalized dimension tables to reduce redundancy in the dimension tables .

Question.7Why need staging area database for DWH?Answer: Staging area needs to clean operational data before loading into data warehouse.

cleaning in the sense your merging data which comes from different source .

Question.8What are the steps to create a database in manually?Answer:create OS service and create init file and start data base no mount stage then give create data base command.

Question.9Difference between OLTP and DWH?Answer:OLTP system is basically application orientation (eg, purchase order it is functionality of an application)

Where as in DWH concern is subject orient (subject in the sense customer, product, item, time) .

Question.10What is the significance of surrogate key?Answer: Surrogate key used in slowly changing dimension table to track old and new values and its derived from primary key.

Question.11What is slowly changing dimension. What kind of scd used in your project?Answer:Dimension attribute values may change constantly over the time. (Say for example customer dimension has customer_id ,name, and address, customer address may change over time.

Question.12Row will you handle this situation?Answer:There are 3 types, one is we can overwrite the existing record, second one is create additional new record at the time of change with the new attribute values.Third one is create new field to keep new values in the original dimension table.

Question.13What is difference between primary key and unique key constraints?Answer:Primary key maintains uniqueness and not null values

Where as unique constrains maintain unique values and null values

Question.14What are the types of index? And is the type of index used in your project?Answer: Bitmap index, B-tree index, Function based index, reverse key and composite index.

We used Bitmap index in our project for better performance.

Question.15A table have 3 partitions but I want to update in 3rd partitions how will you do?Answer:Specify partition name in the update statement. Say for example Update employee partition(name) a, set a.empno=10 where ename=Ashok

Question.16When you give an update statement how memory flow will happen and how oracles allocate memory for that?Answer:Oracle first checks in Shared sql area whether same Sql statement is available if it is there it uses. Otherwise allocate memory in shared sql area and then create run time memory in Private sql area to create parse tree and execution plan. Once it completed stored in the shared sql area wherein previously allocated memory .

Question.17Write a query to find out 5th max salary? In Oracle, DB2, SQL ServerAnswer:Select (list the columns you want) from (select salary from employee order by salary) Where rownum 1. [sociallocker]

Question.3How to you verify a complicated SQL?Answer:I use explain statement to check if the query is doing what I wanted it to do.

Question.4Did u ever use UPPER Function?Answer:UPPER Function is used to convert all characters in a column to the same characters in upper case.

Question.5What does a LOWER Function do?Answer:LOWER function is used to convert all characters in a column to the lower case characters.

Question.6How do you see a DDL for an existing table?Answer:By using show table command.

Question.7Which is more efficient GROUP BY or DISTINCT to find duplicates?Answer:With more duplicates GROUP BY is more efficient, if only a few duplicates exist DISTINCT is more efficient.

Question.8Syntax for CASE WHEN statement?Answer:CASE value_expression_1 WHEN value_expression_n THEN scalar_expression_n END;

Question.9Whats the difference between TIMESTAMP (0) and TIMESTAMP (6)?Answer:TIMESTAMP (0) is CHAR (19) and TIMESTAMP (6) is CHAR (26)

Everything is same except that TIMESTAMP (6) has microseconds too.

Question.10How do you determine the number of sessions?Answer: 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.

Question.11What is node? How many nodes and AMPs used in your previous project?Answer:Node is a database running in a server. We used 318 nodes and each node has 2 to 4 AMPS.

Question.12What is a clique?Answer:Clique is a group of disk arrays physically cabled to a group of nodes.

Question.13Interviewer explained about their project (Environment, nature of work)?Answer:Listen to them carefully so that at the end of the interview you can ask questions about the project when you are given a chance to ask questions.

of the project.

Question.14What is the difference between FastLoad and MultiLoad?Answer:FastLoad uses multiple sessions to quickly load large amount of data on empty table.MultiLoad is used for high-volume maintenance on tables and views. It works with non-empty tables also. Maximum 5 tables can be used in MultiLoad.

Question.15Have you used procedures?Answer:No. I have not used procedures. But I have expertise knowledge writing procedures. My company have not encouraged me to write procedures because it becomes single AMP operation, as such uses lot of resources and expensive in terms of resource and time.

Question.16What is the purpose of indexes?Answer:An index is a mechanism that can be used by the SQL query optimizer to make table access more performant. Indexes enhance data access by providing a more-or-less direct path to stored data and avoiding the necessity to perform full table scans to locate the small number of rows you typically want to retrieve or update.

Question.17What is primary index and secondary index?Answer:Primary index is the mechanism for assigning a data row to an AMP and a location on the AMPs disks. Indexes also used to access rows from a table without having to search the entire table.

Secondary indexes enhance set selection by specifying access paths less frequently used than the primary index path. Secondary indexes are also used to facilitate aggregate operations. If a secondary index covers a query, then the Optimizer determines that it would be less costly to accesses its rows directly rather than using it to access the base table rows it points to. Sometimes multiple secondary indexes with low individual selectivity can be overlapped and bit mapped to provide enhanced

Question.18Why primary and secondary index is used?Answer:Refer answer from previous question.

Question.19What are the things to considered while creating secondary index?Answer:Creating a secondary index causes Teradata to build a sub-table to contain its index rows, thus adding another set of rows that requires updating each time a table row is inserted, deleted, or updated. Secondary index sub-tables are also duplicated whenever a table is defined with FALLBACK, so the maintenance overhead is effectively doubled.[/sociallocker]

Informatica Interview Questions and answers for experienced

Question.1What is the difference between connected and unconnected transformation?Answer:Connected Transformation: Connected transformation is connected to other transformations or directly to target table in the mapping. Unconnected Transformation: An unconnected transformation is not connected to other transformations in the mapping. It is called within another transformation, and returns a value to that transformation.

Question.2What are various types of Aggregation?Answer:Various types of aggregation are

SUM

AVG

vCOUNT

MAX

MIN

FIRST

LAST

MEDIAN

PERCENTILE

STDDEV

VARIANCE. [sociallocker]

Question.3What are Aggregator Transformation?Answer:Aggregator transformation is an Active and Connected transformation. This transformation is useful to perform calculations such as averages and sums (mainly to perform calculations on multiple rows or groups).

Question.4What are Expression transformation?Answer:Expression transformation is a Passive and Connected transformation. This can be used to calculate values in a single row before writing to the target.

Question.5What are Filter transformation?Answer:Filter transformation is an Active and Connected transformation. This can be used to filter rows in a mapping that do not meet the condition.

Question.6What are Joiner transformation?Answer:Joiner Transformation is an Active and Connected transformation. This can be used to join two sources coming from two different locations or from same location.

Question.7Why we use lookup transformations?Answer:Lookup Transformations can access data from relational tables that are not sources in mapping.

Question.8What are Normalizer transformation?Answer:Normalizer Transformation is an Active and Connected transformation. It is used mainly with COBOL sources where most of the time data is stored in denormalized format. Also, Normalizer transformation can be used to create multiple rows from a single row of data.

Question.9 What are Rank transformation?Answer:Rank transformation is an Active and Connected transformation. It is used to select the top or bottom rank of data.

Question.10What are Router transformation?Answer:Router transformationis an Active and Connected transformation. It is similar to filter transformation. The only difference is, filter transformation drops the data that do not meet the condition whereas router has an option to capture the data that do not meet the condition. It is useful to test multiple conditions.

Question.11What are Sorter transformation?Answer:Sorter transformation is a Connected and an Active transformation. It allows to sort data either in ascending or descending order according to a specified field.

Question.12Name four output files that information server creates during session running?Answer:Session Log

Workflow Log

Errors Log

Badfile

Question.13What is the difference between lookup cache and lookup index?Answer:Look up Cache contains Index cache and data cache.

Index cache : Contains columns used in condition.Question.14What are the difference between static cache and dynamic cache?Answer:Dynamic cache decreases the performance in comparisons to static cache.

Static cache do not see such things just insert data as many times as it is coming.

Question.15Define maping and sessions?Answer:Maping: It is a set of source and target definitions linked by transformation objects that define the rules for transformation. Session : It is a set of instructions that describe how and when to move data from source to targets.

Question.16What is a command that used to run a batch?Answer:pmcmd is used to start a batch.

Question.17What is Datadriven?Answer:The informatica server follows instructions coded into update strategy transformations with in the session maping determine how to flag records for insert, update, delete or reject.

Question.18What is power center repository?Answer:The Power Center repository allows you to share metadata across repositories to create a data mart domain.

Question.19What is parameter file?Answer:A parameter file is a file created by text editor such as word pad or notepad. U can define the following values in parameter file.

Maping parameters

Maping variables

session parameters.[/sociallocker]

Informatica Interview Questions and Answers

Question.1What is Data warehouse?Answer:According to Bill Inmon, known as father of Data warehousing. A Data warehouse is a subject oriented, integrated ,time variant, non volatile collection of data in support of managements decision making process.

Question.2What are the types of data warehouses?Answer:There are three types of data warehouses

Enterprise Data Warehouse ODS (operational data store) Data Mart[sociallocker]

Question.3What is Data mart?Answer:A data mart is a subset of data warehouse that is designed for a particular line of business, such as sales, marketing, or finance. In a dependent data mart, data can be derived from an enterprise wide data warehouse. In an independent data mart can be collected directly from sources.

Question.4What is star schema?Answer:A star schema is the simplest form of data warehouse schema that consists of one or more dimensional and fact tables.

Question.5What is snow flake schema?Answer:A Snowflake schema is nothing but one Fact table which is connected to a number of dimension tables, The snowflake and star schema are methods of storing data which are multidimensional in nature.

Question.6What are ETL Tools?Answer:ETL Tools are stands for Extraction, Transformation, and Loading the data into the data warehouse for decision making. ETL refers to the methods involved in accessing and manipulating source data and loading it into target database.

Question.7What are Dimensional table?Answer:Dimension tables contain attributes that describe fact records in the fact table.

Question.8What is data Modelling?Answer:Data Modeling is representing the real world set of data structures or entities and their relationship in their of data models, required for a database.Data Modelling consists of various types like

Conceptual data modeling Logical data modeling Physical data modeling Enterprise data modeling Relation data modeling Dimensional data modeling.Question.9What is Surrogate key?Answer:Surrogate key is a substitution for the natural primary key. It is just a unique identifier or number of each row that can be used for the primary key to the table.

Question.10What is Data Mining?Answer:A Data Mining is the process of analyzing data from different perspectives and summarizing it into useful information.

Question.11What is Operational Data Store?Answer:A ODS is an operational data store which comes as a second layer in a datawarehouse architecture. It has got the characteristics of both OLTP and DSS systems.

Question.12What is the Difference between OLTP and OLAP?Answer:OLTP is nothing but OnLine Transaction Processing which contains a normalisedtables

But OLAP(Online Analtical Programming) contains the history of OLTP data which is non-volatile acts as a Decisions Support System.

Question.13How many types of dimensions are available in Informatica?Answer:There are three types of dimensions available are :

Junk dimension Degenerative Dimension Conformed DimensionQuestion.14What are the designer tools for creating tranformations?Answer:Mapping designer Transformation developer Mapplet designerQuestion.15What is the maplet?Answer:Maplet is a set of transformations that you build in the maplet designer and you can use in multiple mapings.

Question. 16What is Session and Batches?Answer:Session: A session is a set of commands that describes the server to move data to the target.Batch: A Batch is set of tasks that may include one or more numbar of tasks (sessions, ewent wait, email, command, etc).

Question.17What are slowly changing dimensions?Answer:Dimensions that change overtime are called Slowly Changing Dimensions(SCD).

Slowly Changing Dimension-Type1 :Which has only current records.Slowly Changing Dimension-Type2 :Which has current records + historical records.Slowly Changing Dimension-Type3 :Which has current records + one previous records.Question.18What are 2 modes of data movement in Informatica Server?Answer:There are two modes of data movement are:

Normal Mode in which for every record a separate DML stmt will be prepared and executed.

Bulk Mode in which for multiple records DML stmt will be preapred and executed thus improves performance.

Question.19What is the difference between Active and Passive transformation?Answer:Active Transformation:An active transformation can change the number of rows that pass through it from source to target i.e it eliminates rows that do not meet the condition in transformation.Passive Transformation:A passive transformation does not change the number of rows that pass through it i.e it passes all rows through the transformation.[/sociallocker]

Teradata Interview Questions and answers

Question.1What is the difference between FastLoad and MultiLoad?Answer:FastLoad uses multiple sessions to quickly load large amount of data on empty table. MultiLoad is used for high-volume maintenance on tables and views. It works with non-empty tables also. Maximum 5 tables can be used in MultiLoad.

Question.2Which is faster?Answer:FastLoad.

Question.3Difference between Inner join and outer join?Answer:An inner join gets data from both tables where the specified data exists in both tables.

An outer join gets data from the source table at all times, and returns data from the outer joined table ONLY if it matches the criteria.[sociallocker]

Question.4What is multi Insert?Answer:Inserting data records into the table using multiple insert statements. Putting a semi colon in front of the key word INSERT in the next statement rather than terminating the first statement with a semi colon achieves it.

Insert into Sales select * from customer

Insert into Loan select * from customer;

Question.5Is multi insert ANSI standard?Answer:No.

Question.6How do you create a table with an existing structure of another table with data and with no data?Answer:Create table Customer dummy as Customer with data / with no data;

Question.7What is the opening step in Basic Teradata Query script?Answer:Logon tdipid/username, password.

Question.8You are calling a Bteq script, which drops a table and creates a table. It will throw an error if the table does not exist. How can you do it without throwing the error?Answer:You can it by setting error level to zero before dropping and resetting the error level to 8 after dropping.

Question.9ERRORLEVEL (3807)Answer:SEVERITY 8;

Question.10Can you FastExport a field, which is primary key by putting equality on that key?Answer:No.

Question.11Did you write stored procedures in Teradata?Answer:No, because they become a single amp operation and my company didnt encourage that.

Question.12What is the use of having indexs on table?Answer:For faster record search.

Question.13Did you use Query man or SQL assistance?Answer:SQL assistant 6.1

Question.14.I am updating a table in Bteq. It has to update a large number of rows, so its really slow. What do you suggest?Answer:In Teradata it is not recommended to update more than 1 million rows due to journal space problems, if it is less than that and its slow in the Bteq, you might want to add collect statistics statement before the update statement.

Question.15 Is it necessary to add? QUIT statement after a Bteq query when I am calling it in a Unix environment?Answer:Not necessary but it is good to add a QUIT statement after a query.

Question.16There is a column with date in it. If I want to get just month how It can be done? Can I use sub string?Answer: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 its a time stamp (select extract (minute from column name).

Question.17Whats the syntax of sub string?Answer:SUBSTRING (string_expression, n1 [n2])

Question.18Did you use CASE WHEN statement. Can you tell us a little about it?Answer:Yes. When a case has to be selected depending upon the value of the expression.

Question.19While creating table my DBA has FALLBACK or NO FALLBACK in his DDL. What is that?Answer: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.[/sociallocker]