SSIS/SSAS/SSRS/SQL
Server /Data Warehouse Interview Questions and answers
SSIS
1. What is a
package?
a).a discrete executable unit of work composed of a collection of control flow
and other objects, including data sources, transformations, process sequence,
and rules, errors and event handling, and data destinations.
2. What is a workflow in SSIS?
a).`a workflow is a set of instructions on how to execute Tasks.
(It is a set of instructions on how to execute Tasks such as sessions, emails
and shell commands. a workflow is created form work flow mgr.)
3. What is the Difference between
control flow Items and data flow Items?
a).the control flow is the highest level control process. It allows you to
manage the run-time process the run time process activities of data flow and
other processes within a package.
When we want to extract, transform and load data within a package. You add an SSIS
dataflow Task to the package control flow.
4. What are the main components of SSIS (project-architecture)?
A).SSIS architecture has 4 main components
1.SSIS service
2.SSIS runtime engine & runtime executables
3.SSIS dataflow engine & dataflow components
4.SSIS clients’
5.different components in SSIS package?
1. Control flow
2.data flow
3.event handler
4.package explorer
Containers: provide structure and
scope to your package
Types of containers:
i. Task host container: the Taskhost
container services a single Task.
ii. Sequence container: It can
handle the flow of subset of a package and can help you drive a package into
smaller more manageable process.
Uses:-
1. Grouping Tasks so that you can disable a part of the package that no
longer needed.
2. Narrowing the scope of the variable to a container.
3. Managing the property of multiple Tasks in one step by setting the
properties of the container.
iii. For loop container: evaluates
an expression and repeats Its workflow until the expression evaluates to false.
iv. For each loop container: defines
a control flow repeatedly by using an enumerator.
For each loop container repeats the
control flow for each member of a specified enumerator.
Tasks: It provides the functionality
to your package.
Ø It is a individual unit of work.
Event handler: It responds to raised
events in your package.
Precedence constraints: It provides
ordinal relationship b/w various Items in your package.
6. How to deploy the package?
To deploy the package first we need to configure some properties.
Ø Go to project tab->package properties->we get a window, configure
deployment Utility as "True"
Ø Specify the path as "bin/deployment"
7. Connection manager:
a).It is a bridge b/w package object and physical data. It provides logical
representation of a connection at design time the properties of the connection
mgr describes the physical connection that integration services creates when
the package is run.
8. Tell the Utility to execute (run) the
package?
a) In BIDS a package that can be executed in debug mode by using the debug menu
or toolbar or from solution explorer.
In production, the package can be executed from the command line or from
Microsoft windows Utility or It can be scheduled for automated execution by
using the SQL server agent.
i). Go to->debug menu and select the start debugging button
ii).press F5 key
iii).right click the package and choose execute package.
iv).command prompts utilities
a).DTExecUI
1. To open command prompt->run->type dtexecui->press enter
2. The execute package Utility dialog box opens.
3. in that click execute to run the package.
Wait until the package has executed successfully.
b).DTExec Utility
1.open the command prompt window.
2. Command prompt window->type dtexec /followed by the DTS, SQL, or file
option and the package path, including package name.
3. If the package encryption level is encrypting sensitive with password or
encrypt all with password, use the decrypt option to provide the password.
If no password is included, dtexec will prompt you for the password.
4. Optionally, provide additional command-line options
5. Press enter.
6. Optionally, view logging and reporting information before closing the
command prompt window.
The execute package Utility dialog box opens.
7. In the execute package Utility dialog box, click execute package.
Wait until the package has executed successfully.
v).using SQL server mgmt studio to execute package
1. In SSMS right click a package, and then click run package.
Execute package Utility opens.
2. Execute the package as described previously.
9. How can u design SCD in SSIS?
a) Def:-SCD explains how to capture the changes over the period of time.
This is also known as change data capture.
type1: It keeps the most recent
values in the target. It does not maintain the history.
type2: It keeps the full history in
the target database. For every update in the source a new record is inserted in
the target.
type3: It keeps current &
previous information in the target.
10. How can u handle the errors through the help of logging in SSIS?
a) To create an on error event handler to which you add the log error execute SQL
Task.
11. What is a log file and how to send
log file to mgr?
a) It is especially useful when the package has been deployed to the production
environment, and you cannot use BIDS and VSA to debug the package.
SSIS enables you to implement logging code through the Dts. Log method.
When the Dts. Log method is called in the script, the SSIS engine will route
the message to the log providers that are configured in the containing package.
12. What is environment variable in
SSIS?
a) An environment variable configuration sets a package property equal to the
value in an environment variable.
Environmental configurations are useful for configuring properties that are
dependent on the computer that is executing the package.
13. about multiple configurations?
a) It means including the xml configuration, environment variable, registry
entry, parent package variable, SQL Server table, and direct and indirect
configuration types.
14. How to provide security to packages?
a) In two ways
1. Package encryption
2. Password protection.
15. as per error handling in T/R, which
one handle the better performance? Like fail component, redirect row or ignore
failure?
a) Redirect row provides better performance for error handling.
16. Staging area??
a) It is a temporary data storage location. Where various data T/R activities
take place.
Staging
area is a kitchen of data warehouse.
17. Task??
a) An individual unit of work.
Types:-
1.
Active x script Task
2. Analysis services execute DDL Task *
3. Analysis services processing Task *
4. Bulk insert Task *
5. Data flow Task *
6. Data mining query Task
7. Execute Dts 2000 package Task
8. Execute package Task *
9. Execute process Task
10. Execute SQL Task *
11. File system Task *
12. Ftp Task
13. Message queue Task
14. Script Task *
15. Send mail Task *
16. Web service Task
17. Wmi data reader Task
18. Wmi event Task
19. Xml Task
18. Event handler & logging?
Even handler is the mechanism to raise a event based on specific scenario. For
example if there is any failure in data load it will notify thru email or entry
in error table etc.
Logging
can be done based on event, in SSIS there are 12 events that can be logged at Task
or package level. You can enable partial logging for one Task and enable much
more detailed logging for billing Tasks.
Example:-
On error; On post validate; On progress; On warning
In SSIS different type of logging mechanism are there:
SQL
profiler
Text files
SQL server
Window event log
Xml file
19. Import & export wizard?
a) Easiest method to move data from sources like oracle, db2, SQL server.
Right click on database name->go to Task->import and export wizard
Select the source
Select the destination
Query copy of tables
Execute
Finish
20.what solution explorer?
Once you creating project with specific project name then if you want to add
data source/-data source views/packages/ miscellaneous; then this window will
help to organize different files under one structure.
21. Precedence constraints?
a) Constraints that link executable, container, and Tasks within the package
control flow and specify condition that determine the sequence
and conditions for determine whether executable run.
22. Data pipeline?
a) The memory based, multithreaded, buffered t/r process flow data through an SSIS
data flow Task during package execution.
23. TRANSFORMATIONS??
It is an object that generates, modifies, or passes data.
1. AGGEGATE T/R:-It applies an aggregate function to grouped records and
produces new output records from aggregated results.
2. AUDIT T/R:-the t/r adds the value of a system variable, such as machine name
or execution instance GUID to a new output column.
3. CHARACTER MAP T/R:-this t/r makes string data changes such as changing data
from lower case to upper case.
4. CONDITIONAL SPLIT:-It separate input rows into separate output data
pipelines based on the Boolean expressions configured for each output.
5. COPY COLUMN:-add a copy of column to the t/r output we can later transform
the copy keeping the original for auditing personal
6.DATA CONVERSION:-converts a columns data type to another data type.
7. DATA MINING QUERY:-perform a data mining query against analysis services.
8. DERIVED COLUMN:-create a new derive column calculated from expression.
9. EXPORT COLUMN:-It allows you to export a column from the data flow to a
file.
10. FUZZY GROUPING:-perform data cleansing by finding rows that are likely
duplicates.
11. FUZZY LOOKUP:-matches and standardizes data based on fuzzy logic.
Ex:-transform the name jon to john
12.IMPORT COLUMN:-reads the data from a file & adds It into a dataflow.
13. LOOKUP:-perform the lookup of data to be used later in a transform.
Ex:-t/T to lookup a city based on zip code.
1. Getting a related value from a table using a key column value
2. Update slowly changing dimension table
3.to check whether records already exist in the table.
14. MERGE:-merges two sorted data sets into a single data set into a single
data flow.
15. MERGE JOIN:-merges two data sets into a single dataset using a join
junction.
16. MULTI CAST:-sends a copy of two data to an additional path in the workflow.
17. ROW COUNT:-stores the rows count from the data flow into a variable.
18. ROW SAMPLING:-captures the sample of data from the dataflow by using a row
count of the total rows in dataflow.
19. ROW SAMPLING:-captures the sample of the data from the data flow by using a
row count of the total rows in data flow.
20. UNION ALL:-merge multiple data sets into a single dataset.
21. PIVOT:-converts rows into columns
22.UNPIVOT:-converts columns into rows
24. Batch?
a) A batch is defined as group of sessions. Those are 2 types.
1. Parallel batch processing
2. Sequential batch processing
to execute a SSIS package we will use "execute package utility"
To deploy a SSIS package we will use "package deployment Utility”
SSRS:--
1. What are the main components of
reporting services?
a) Report designer, report server, report manager, report user.
2. Where can u publish the report?
a) By using report designer or publish reports on report server.
3. What are the necessity things for
creating matrix report?
a) Page, column, row, details
4. For generating reports which is used like RDBMS OR CUBE?
a) Depends on data; report can be developed using different source like
database tables/cube/text files etc.
5. What is .rdl file?
a) .rdl is a Report Definition Language. Every report saves with .rdl extension.
SSAS:-
1. What are the fixed measure and
calculated measure?
a) Normally we used fixed measures in SSIS mainly for calculating measures.
Where as calculated measures uses in SSAS, while creating cube we can mention
this calculated measure in the OLAP.
2. What are measures?
a) Measures are numeric data based on columns in a fact table.
3. What are cubes?
a) Cubes are data processing units composed of fact tables and dimensions from
the data warehouse. They provided multidimensional analysis.
4. What are virtual cubes?
These are combination of one or more real cubes and require no disk space to
store them. They store only definition and not the data.
DATAWARE HOUSE CONCEPTS:-
1. Difference b/w OLTP AND OLAP?
OLTP
|
OLAP
|
1.transactional processing
|
1.query processing
|
2.time sensitive
|
2.history oriented
|
3. Operator & clerks view
|
3.Managers, CEOs, PM’s views
|
4. Organized by transaction
(Order, input, inventory)
|
4.organized
by subjects
(product, customer)
|
5.relatively smaller DB
|
5.large DB size
|
6.volatile data
|
6.non-volatile
|
7.stores all data
|
7.stores relevant data
|
8. Not flexible
|
8.flexible
|
2. Difference b/w star schema and
snowflake?
STAR Schema
|
Snowflake Schema
|
1 centrally located fact table surrounded by de
normalize dimension table
|
1 Centraly located fact table surrounded by the
normalized dimension table
|
2 All dimensions will be linked directly with
fact table
|
2 All dim link wIth each other (or)
1-N relationship with other table
|
3 It is easy to understand the design
|
3 It is difficult to understand
|
4 We can easily retrieve data parsing the query
against the Fact and Dim table
|
4 It is difficult to retrieve the data while
|
5 Increase the query performance because it
involve less joins
|
5 more joins
|
What are fact tables?
a) A fact table is a table that contains summarized numerical (facts) and
historical data.
This fact table has a foreign key-primary key relation with a dimension table. The
fact table maintains the information in 3rd normal form.
3. Types of facts?
a)
1. Additive:-able to add the facts along with all the dimensions
-discrete numerical measures.
-Ex:-retail sales in $
2. Semi additive:-snapshot taken at a point in time
- Measure of intensity
-not additive along time dimensions
ex:-account balance, inventory balance
3.non-addItive:-numerical measures that can't be added across any dimensions.
Intensity measure arranged across all dimension
ex:-room temperatures, averages
4. Data warehouse?
a) A data ware house is a collection of data marts representing historical data
from Difference operational data sources (OLTP).
The data from these OLTP are structured and optimized for querying and data
analysis in a data warehouse.
5. Data mart?
a) A data mart is a subset of a data warehouse that can provide data for
reporting and analysis on a section, unit or a department like sales dept, hr
dept.
6. What is OLAP?
a) OLAP stands for online analytical processing. It uses databases tables (fact
and dimension table) to enable multi dimensional viewing, analysis and querying
of large amount of data.
7. What is OLTP?
a) OLTP stands for online transactional processing. Except data warehouse
databases the other databases are OLTP.
These OLTP uses normalized schema structure.
These OLTP databases are designed for recording the daily operations and
transactions of a business.
8. What are dimensions?
Dimensions are categories by which summarized data can be viewed. For example a
profit summary fact table can be viewed by a time dimension.
9. What are conformed dimension?
a) The dimensions which are reusable and fixed in nature. Example customer,
time, geography dimensions.
10. Staging area?
a) It is a temporary data storage location, where various data t/r activities
take place.
11. Fact grain (granularity)?
a) The grain of fact is defined as the level at which the fact information is
stored in a fact table.
12. What is a fact less fact table?
a) The fact table which does not contain facts is called as fact table.
Generally when we need to combine two data marts, then one data mart will have
a fact less fact table and other one with common fact table.
13. What are measures?
a) Measures are numeric data based on columns in a fact table.
14. What are cubes?
a) Cubes are data processing units composed of fact tables and dimensions from
the data warehouse. They provided multidimensional analysis.
15. What are virtual cubes?
These are combination of one or more real cubes and require no disk space to
store them. They store only definition and not the data.
16. SCD's?
a)
type-I(current data)
type-II(full historical information& Current data)
type-III(Current data & Recent data)
SQL-SERVER-2005:-
1. Surrogate key?
a) It is an artificial or synthetic key that is used as a substitute for a
natural keys.
It is just a unique identifier or number for each row that can be used for the
primary key to the table.
(It is a sequence generate key which is assigned to be a primary key in the
system(table)).
2. Primary key?
a) It can be used to uniquely identify every row of the table.
Unique + not null
3. Foreign key?
a) It is a column r combination of columns that contain values that are found in
primary key of some table.
It may be null, not unique.
4. ComposIte key?
a) It is a primary key consisting of more than one column.
4. Indexes?
a) It is an access strategy that is a way to sort and search records in the
table.
Indexes are essential to improve the speed with which records can be located
and retrieved from a table.
Types: - cluster index (can create only one index on table)
Non-cluster index (can create up to 249 indexes on table)
Unique index
Composite index
(Simple index, reverse key index, bitmap index, function index)
5. View?
a) It is used for data security reason
to reduce the redundant data.
6. Cluster?
a) 1-many access path.
Clusters are used to store data from Difference tables in the same physical
data blocks.
7. Sequences?
a) It is used to quickest way to retrieve the data.
8. Cursors?
a) Implicit cursor
explicit cursor
Parameter cursor
9. Triggers?
a) Row trigger
Statement trigger
10. Transactions?
Save point
Commit & rollback.
11. Security?
a) Encryption
Locking
Level of locking row level, page level, table level
12.constraints?
primary
foreign(reference)
check
unique
13. Difference b/w having and where?
a) after performing 'group by' operation 'having will again filter the records
based on having condition
'where' is used to filter the data based on a condition and It applies to retrieve
on a particular column.
14. Joins?
a) Join can combine the information from two tables into a single unit.
Inner join:-
they matched the records together based on one or more common fields (matched-records
only).
Outer join:-
full join:-It combines the all rows on both sides of the join.
Cross join:-
15. Union & union-all?
a) Union:-columns, data types should be same
Select distinct values
Remove duplicates
Union-all:-displays all the rows exact & duplicates.
16. Difference b/w drop, delete &
truncate?
Delete:-delete all rows at a time
delete a single row data based on condition.
Memory allocation will be there
structure will be there
Truncate:-delete all rows at a time
can't delete single row at a time
memory allocation deleted
table structure will be there
Drop: - delete all rows at a time
can't delete single row at a time
memory allocation can be deleted
table structure also be deleted
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