DWBI Interview Questions & Answers

Question 1. How To Test Database In Manually? Explain With An Example

Answer :

Observing that operations, which are operated on front-end is effected on back-end or not.

The approach is as follows : While adding a record the’ front-end check back-end that addition of record is effected or not. So same for delete, update,…… Ex:Enter employee record in database thr’ front-end and check if the record is added or not to the back-end(manually).

Question 2. What Is Data Driven Test?

Answer :

Data driven test is used to test the multi numbers of data in a data-table, using this we can easy to replace the parameters in the same time from different locations.

e.g: using .xsl sheets.

Question 3. How To Check A Trigger Is Fired Or Not, While Doing Database Testing?

Answer :

It can be verified by querying the common audit log where we can able to see the triggers fired.

Question 4. How To Test Database Procedures And Triggers?

Answer :

Before testing Data Base Procedures and Triggers, Tester should know that what is the Input and out put of the procedures/Triggers, Then execute Procedures and Triggers, if you get answer that Test Case will be pass other wise fail.

These requirements should get from DEVELOPER

Question 5. Is A “a Fast Database Retrieval Rate” A Testable Requirement?

Answer :

No. I do not think so. Since the requirement seems to be ambiguous. The SRS should clearly mention the performance or transaction requirements i.e. It should say like ‘A DB retrieval rate of 5 micro sec’.

Question 6. How To Test A Dts Package Created For Data Insert Update And Delete? What Should Be Considered In The Above Case While Testing It? What Conditions Are To Be Checked If The Data Is Inserted, Updated Or Deleted Using A Text Files?

Answer :

Data Integrity checks should be performed. IF the database schema is 3rd normal form, then that should be maintained.

Check to see if any of the constraints have thrown an error. The most important command will have to be the DELETE command. That is where things can go really wrong.

Most of all, maintain a backup of the previous database.

Question 7. How Do You Test Whether A Database In Updated When Information Is Entered In The Front End?

Answer :

It depend on your application interface..

1. If your application provides view functionality for the entered data, then you can verify that from front end only. Most of the time Black box test engineers verify the functionality in this way. 
2. If your application has only data entry from front end and there is no view from front end, then you have to go to Database and run relevent SQL query.
3. You can also use database checkpoint function in WinRunner.

Question 8. How Do You Test Whether The Database Is Updated As And When An Information Are Added In The Front End?give Me An Example?

Answer :

It depends on what level of testing you are doing.When you want to save something from front end obviously, it has to store somewhere in the database You will need to find out the relevant tables involved in saving the records.

Data Mapping from front end to the tables.Then enter the data from front end and save.

Question 9. What Steps Does A Tester Take In Testing Stored Procedures?

Answer :

First the tester should to go through the requirement, as to why the particular stored procedure is written for.

Then check whether all the required indexes, joins, updates, deletions are correct comparing with the tables mentions in the Stored Procedure. And also he has to ensure whether the Stored Procedure follows the standard format like comments, updated by, etc.

Then check the procedure calling name, calling parameters, and expected reponses for different sets of input parameters.

Then run the procedure yourself with database client programs like TOAD, or mysql, or Query Analyzer Rerun the procedure with different parameters, and check results against expected values.

Finally, automate the tests with WinRunner.

Question 10. What Are The Different Stages Involved In Database Testing

Answer :

• verify field level data in the database with respect to front-end transactions
• verify the constraint (primary key,foreign key ….)
• verify the performance of the procedures
• verify the triggers (execution of triggers)
• verify the transactions (begin,commit,rollback)

Question 11. How To Use Sql Queries In Winrunner/qtp In Qtp?

Answer :

Using output database check point and database check point , select SQL manual queries option and enter the “select” quires to retrieve data in the database and compare the expected and actual

Question 12. What Is Database Testing And What We Test In Database Testing?

Answer :

Database testing is all about testing joins, views, imports and exports , testing the procedures, checking locks, indexing etc. Its not about testing the data in the database.

Usually database testing is performed by DBA.

Question 13. What Sql Statements Have You Used In Database Testing?

Answer :

The most important statement for database testing is the SELECT statement, which returns data rows from one or multiple tables that satisfies a given set of criteria.

You may need to use other DML (Data Manipulation Language) statements like INSERT, UPDATE and DELETE to manage your test data.

You may also need to use DDL (Data Definition Language) statements like CREATE TABLE, ALTER TABLE, and DROP TABLE to manage your test tables.

You may also need to some other commands to view table structures, column definitions, indexes, constraints and store procedures.

Question 14. How To Test Data Loading In Data Base Testing?

Answer :

You have to do the following things while you are involving in Data Load testing.

1. You have know about source data (table(s), columns, datatypes and Constraints)
2. You have to know about Target data (table(s), columns, datatypes and Constraints)
3. You have to check the compatibility of Source and Target.
4. You have to Open corresponding DTS package in SQL Enterprise Manager and run the DTS package (If you are using SQL Server).
5. Then you should compare the column’s data of Source and Target.
6. You have to check the number to rows of Source and Target.
7. Then you have to update the data in Source and see the change is reflecting in Target or not.
8. You have to check about junk character and NULLs.

Question 15. What Is Way Of Writing Test Cases For Database Testing?

Answer :

Data base testing basically include the following.

1. Data validity testing: For doing data validity testing you should be good in SQL queries
2. Data Integrity testing: For data integrity testing you should know about referential integrity and different constraint.
3. Performance related to data base: For performance related things you should have idea about the table structure and design.
4. Testing of Procedure,triggers and functions: For testing Procedure triggers and functions you should be able to understand the same.

Question 16. What We Normally Check For In The Database Testing?

Answer :

In DB testing we need to check for,

1. The field size validation
2. Check constraints.
3. Indexes are done or not (for performance related issues)
4. Stored procedures
5. The field size defined in the application is matching with that in the db.

Question 17. Which Sql Statements Have You Used For Testing Databases?

Answer :

In DB testing we need to check for,

1. The field size validation
2. Check constraints.
3. Indexes are done or not (for performance related issues)
4. Stored procedures
5. The field size defined in the application is matching with that in the db.

Question 18. What Is Used To Check Data Loading During Database Testing?

Answer :

Query analyzer can be used to check data loading. 3.

Question 19. How Should Test Cases Be Written For Database Testing?

Answer :

Test cases for database testing should include the following information: project name, module name, bug ID number, test objective, steps/actions, expected results, actual results, status, priority of defect, and severity of defect.

Question 20. What Is Typically Checked During Database Testing?

Answer :

The following items are typically checked during database testing:

• Validation of field size (application matches what resides in database)
• Constraints
• Indexes (associated with performance related issues)
• Stored procedures

Question 21. Provide An Example Of What Can Be Manually Tested In A Database.

Answer :

Non-editable fields through the database can be tested manually. For example, a field that is non-editable through the front end, should not allow a user to add a record to the database.

Question 22. What Are The Different Types Of Join Conditions In Sql?

Answer :

Inner join, Outer Join, Left outer join, Right outer join. And try to explain each of them if he gives time.

Question 23. How Can You Retrieve Unique Rows From A Table?

Answer :

I can do that by using a DISTINCT keyword in my sql query. eg: select DISTINCT * from products where product_category = ‘Electronics’;

Question 24. How Do Sql Queries Will Effect The Performance Of The Application?

Answer :

Yes, sql queries make a lot of impact on the whole performance of application. A poorly written sql query by a developer can take long time to generate a report or retrieve data from data base. So, we need to take few precautions while writing queries, as a database tester I will also review the queries written by a developer. For example: get rid of nested sql queries as much as possible and make use of joins.

Question 25. What Is Drill-through?

Answer :

Drill through is the process of going to the detail level data from summary data.

Consider the above example on retail shops. If the CEO finds out that sales in East Europe has declined this year compared to last year, he then might want to know the root cause of the decrease. For this, he may start drilling through his report to more detail level and eventually find out that even though individual shop sales has actually increased, the overall sales figure has decreased because a certain shop in Turkey has stopped operating the business. The detail level of data, which CEO was not much interested on earlier, has this time helped him to pin point the root cause of declined sales. And the method he has followed to obtain the details from the aggregated data is called drill through.

Question 26. What Is Slicing-dicing?

Answer :

Slicing means showing the slice of a data, given a certain set of dimension (e.g. Product) and value (e.g. Brown Bread) and measures (e.g. sales).

Dicing means viewing the slice with respect to different dimensions and in different level of aggregations.

Slicing and dicing operations are part of pivoting.

Question 27. What Is Aggregation And What Is The Benefit Of Aggregation?

Answer :

A data warehouse usually captures data with same degree of details as available in source. The "degree of detail" is termed as granularity. But all reporting requirements from that data warehouse do not need the same degree of details.

To understand this, let's consider an example from retail business. A certain retail chain has 500 shops accross Europe. All the shops record detail level transactions regarding the products they sale and those data are captured in a data warehouse.

Each shop manager can access the data warehouse and they can see which products are sold by whom and in what quantity on any given date. Thus the data warehouse helps the shop managers with the detail level data that can be used for inventory management, trend prediction etc.

Now think about the CEO of that retail chain. He does not really care about which certain sales girl in London sold the highest number of chopsticks or which shop is the best seller of 'brown breads'. All he is interested is, perhaps to check the percentage increase of his revenue margin across Europe. Or may be year to year sales growth on eastern Europe. Such data is aggregated in nature. Because Sales of goods in East Europe is derived by summing up the individual sales data from each shop in East Europe.

Therefore, to support different levels of data warehouse users, data aggregation is needed.

Question 28. What Are Incident And Snapshot Facts?

Answer :

A fact table stores some kind of measurements. Usually these measurements are stored (or captured) against a specific time and these measurements vary with respect to time. Now it might so happen that the business might not able to capture all of its measures always for every point in time. Then those unavailable measurements can be kept empty (Null) or can be filled up with the last available measurements. The first case is the example of incident fact and the second one is the example of snapshot fact.

Question 29. What Is A Fact-less-fact?

Answer :

A fact table that does not contain any measure is called a fact-less fact. This table will only contain keys from different dimension tables. This is often used to resolve a many-to-many cardinality issue.

Explanatory Note: Consider a school, where a single student may be taught by many teachers and a single teacher may have many students. To model this situation in dimensional model, one might introduce a fact-less-fact table joining teacher and student keys. Such a fact table will then be able to answer queries like,

1. Who are the students taught by a specific teacher.
2. Which teacher teaches maximum students.
3. Which student has highest number of teachers.etc. etc.

Question 30. What Is A Mini Dimension?

Answer :

Mini dimensions can be used to handle rapidly changing dimension scenario. If a dimension has a huge number of rapidly changing attributes it is better to separate those attributes in different table called mini dimension. This is done because if the main dimension table is designed as SCD type 2, the table will soon outgrow in size and create performance issues. It is better to segregate the rapidly changing members in different table thereby keeping the main dimension table small and performing.

Question 31. What Is Scd?

Answer :

SCD stands for slowly changing dimension, i.e. the dimensions where data is slowly changing. These can be of many types, e.g. Type 0, Type 1, Type 2, Type 3 and Type 6, although Type 1, 2 and 3 are most common. Read this article to gather in-depth knowledge on various SCD tables.

Question 32. What Is A Role-playing Dimension?

Answer :

Dimensions are often reused for multiple applications within the same database with different contextual meaning. For instance, a "Date" dimension can be used for "Date of Sale", as well as "Date of Delivery", or "Date of Hire". This is often referred to as a 'role-playing dimension'.

Question 33. What Is Junk Dimension?

Answer :

A junk dimension is a grouping of typically low-cardinality attributes (flags, indicators etc.) so that those can be removed from other tables and can be junked into an abstract dimension table.

These junk dimension attributes might not be related. The only purpose of this table is to store all the combinations of the dimensional attributes which you could not fit into the different dimension tables otherwise. Junk dimensions are often used to implement Rapidly Changing Dimensions in data warehouse.

Question 34. What Is Degenerated Dimension?

Answer :

A degenerated dimension is a dimension that is derived from fact table and does not have its own dimension table.

A dimension key, such as transaction number, receipt number, Invoice number etc. does not have any more associated attributes and hence can not be designed as a dimension table.

Question 35. What Is A 'conformed Dimension'?

Answer :

A conformed dimension is the dimension that is shared across multiple subject area. Consider 'Customer' dimension. Both marketing and sales department may use the same customer dimension table in their reports. Similarly, a 'Time' or 'Date' dimension will be shared by different subject areas. These dimensions are conformed dimension.

Theoretically, two dimensions which are either identical or strict mathematical subsets of one another are said to be conformed.

Question 36. What Are The Different Types Of Dimension?

Answer :

In a data warehouse model, dimension can be of following types,

1. Conformed Dimension
2. Junk Dimension
3. Degenerated Dimension
4. Role Playing Dimension

Based on how frequently the data inside a dimension changes, we can further classify dimension as

1. Unchanging or static dimension (UCD)
2. Slowly changing dimension (SCD)
3. Rapidly changing Dimension (RCD)

You may also read, Modeling for various slowly changing dimension and Implementing Rapidly changing dimension to know more about SCD, RCD dimensions etc.