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Interview Questions and Answers for 'Database' - 120 question(s) found - Order By Rating

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 Q1. What is the main difference between unique key and primary key ?Database
Ans. Primary key will not accept NULL values whereas Unique key can accept one NULL value.

A table can have only primary key whereas there can be multiple unique key on a table.

A Clustered index automatically created when a primary key is defined whereas Unique key generates the non-clustered index.

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   Like         Discuss         Correct / Improve     Unique Key  Primary Key     Asked in 1 Companies


 Q2. How would you design the database schema for an event?Database
Ans. Broad question, but if the company need velocity, think about use a NO SQL instead of regular SQL databases.

Also prefers materialized views instead of joins to fetch data quickly.

Regarding the database design, there are very good design tools for professional database (to develop proper indexes and good database design) one of the best is QuickDBD

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   Like         Discuss         Correct / Improve     database design  database schema     Asked in 1 Companies


 Q3. differences between drop , delete and truncateDatabase
 This question was recently asked at 'HCL Technologies'.This question is still unanswered. Can you please provide an answer.


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 Q4. What is a composite primary key and foreign key ?Database
Ans. The combination of values from multiple columns in the composite primary key must be unique for each row in the table.
A foreign key, on the other hand, is a field or set of fields in one table that refers to the primary key in another table. It establishes a relationship between two tables based on the values of the foreign key and the primary key.

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 Q5. How can we increase the speed of SQL queries ?Database
Ans. Using -
1. Prepared Statements
2. Using Indices
3. Using whereby clause only on indexed columns

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 Q6. Explain Working of joins in sql.Database
 This question was recently asked at 'InfoGain'.This question is still unanswered. Can you please provide an answer.


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 Q7. SQL Questions.Database
 This question was recently asked at 'Eurofins IT Solutions'.This question is still unanswered. Can you please provide an answer.


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 Q8. Write SQL query to join 2 tables ?SQL
Ans. Select * from table1 join Select * from table2

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 Q9. Differences between MongoDB and mysql.Database
 This question was recently asked at 'RiseSmart'.This question is still unanswered. Can you please provide an answer.


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 Q10. Create DB schema for Employee, Department.Database
 This question was recently asked at 'RiseSmart India,RiseSmart'.This question is still unanswered. Can you please provide an answer.


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   Like         Discuss         Correct / Improve     db schema  database schema  database design     Asked in 2 Companies


 Q11. Sort an Employee Object based on Name or AgeDatabase
Ans. Use Comparable or Comparator interface

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 Q12. What is the minimum number of tables required to perform a SQL join?Database
Ans. 1 , We can do self join


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 Q13. Can we load Yaml files into AWS DynamoDB ?Amazon Web Services (AWS)
Ans. No

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   Like         Discuss         Correct / Improve     aws dynamodb  aws nosql database  amazon cloud nosql database


 Q14. Difference between composite , primary and unique key ?Database
 This question was recently asked at 'Thomson reuters'.This question is still unanswered. Can you please provide an answer.


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 Q15. create an SQL query across multiple tables involving outer joins Database
Ans. Select * from table1 t1Left outer join table2 t2 on t1.tid = t2.id

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 Q16. What are the factors on which RedShift is priced on ?Amazon Web Services (AWS)
Ans. Compute Node Hours
Backup
Data Transfer

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   Like         Discuss         Correct / Improve     aws data warehouse  aws database  aws redshift


 Q17. What is the ideal use case for DynamoDB ?Amazon Web Services (AWS)
Ans. Fast reads
Much more reads than writes

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   Like         Discuss         Correct / Improve     aws dynamodb  aws nosql database  amazon cloud nosql database


 Q18. What is the limit of read replicas per database ?Amazon Web Services (AWS)
Ans. 5

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   Like         Discuss         Correct / Improve     aws rds  aws database  amazon cloud database  aws rds  aws database  amazon cloud database read replica


 Q19. Difference between multi AZ RDS and Read replicas ?Amazon Web Services (AWS)
Ans. Multi AZ RDS is for disaster recovery and failover whereas Read replicas are for scaling.

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 Q20. What happens to backups if we delete the RDS instance ?Amazon Web Services (AWS)
Ans. Automated Backups are deleted automatically whereas Snapshots are preserved. Upon terminating RDS instance , AWS gives a warning about that and requests to create a final snapshot before terminating the instance.

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 Q21. How would you securely migrate a database to RDS?Amazon Web Services (AWS)
 This question was recently asked at 'Cognizant (C?TS),Overstock'.This question is still unanswered. Can you please provide an answer.


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   Like         Discuss         Correct / Improve     aws rds  aws database  amazon cloud database     Asked in 2 Companies


 Q22. Difference between indexing and partioningDatabase
Ans. Creating an index creates a separate table. ... Indexes are used to speed the search of data within tables. Partitions provide segregation of the data at the hdfs level, creating sub-directories for each partition. Partitioning allows the number of files read and amount of data searched in a query to be limited

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   Like         Discuss         Correct / Improve     indexing  partitioning     Asked in 3 Companies


 Q23. Have you heard of volatile Table in Teradata ?Teradata
Ans. If you create table with VOLATILE option, the life of the table will be only for the current session.
It will be automatically dropped by Teradata manager once session expires.

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 Q24. Given an Employee Table with Salary Column, Find 2nd and 5th highest salary in a particular department.SQL
Ans. Select salary from (select salary from employee where department = order by salary desc limit 5) emp order by salary limit 1 AND Select salary from (select salary from employee where department = order by salary desc limit 2) emp2 order by salary limit 1

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 Q25. Write SQL to get all members and the count of books they have checked out , even the ones that haven't checked out anything.SQL
 This question was recently asked at 'Canopy Tax'.This question is still unanswered. Can you please provide an answer.


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Library Management System has always been the favorite question. This questions is asked irrespective of level.
 Q26. Write data models and service end points for Library Management System ?Architecture
Ans. Following could be the business sub domains or database schemas in such a system

1. Users / Members
2. Sourcing
3. Inventory Management
4. Operations

Following services end points could be there

1. Users - addNewUser ( put ), removeUser ( post )
2. Sourcing - addSupplier ( put ), removeSupplier ( post )
3. Inventory Management - getInventory ( get )
4. Operations - checkIn ( post ), checkout ( post )

There could be following Tables in Database

1. Users / Members - MEMBER, MEMBERSHIP_TYPE
2. Sourcing - SUPPLIER, SUPPLIER_PRODUCT, PRODUCT_REORDER_LEVELS
3. Inventory Management - INVENTORY,PRODUCTS
4. Operations - TRANSACTION

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 Q27. Design database schema for Facebook like application.Database
 This question was recently asked at 'Symantec'.This question is still unanswered. Can you please provide an answer.


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   Like         Discuss         Correct / Improve     database design     Asked in 1 Companies      expert


 Q28. What are different in memory data structures that are used in No Sql Database ?NoSql Database
 This question is still unanswered. Can you please provide an answer.


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 Q29. What are the components of Data Warehousing ?Database
 This question is still unanswered. Can you please provide an answer.


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 Q30. What are scrollable ResultSet?Database
 This question is still unanswered. Can you please provide an answer.


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