Interview Questions and Answers for 'Database' | Search Interview Question

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Q71. If Table A has 100 records and Table B has 50 records , how many records will the equi join of Table generate ?

SQL

Ans. It depends on the join condition.

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Q72. If Table A has 100 records and Table B has 50 records , how many records will the left join of Table A with Table B generate ?

SQL

Ans. 100 records

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Q73. If Table A has 100 records and Table B has 50 records , how many records will the right join of Table A with Table B generate ?

SQL

Ans. 50 records

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Q74. If Table A has 0 records and Table B has 50 records , how many records will the equi join of Table generate ?

SQL

Ans. 0 records

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Q75. What is ORM or Object Relationship Mapping ?

Database

Ans. ORM is the mapping technique, which maps object with relational data model. As we know that in java we need objects we can not user data in relational(in table form). So ORM is set of guideline which allows us to map relational data model in object form.

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Q76. Write a SQL to remove records with a duplicate field in a Table ?

Database

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Q77. How Cassandra provides better Read performance than Oracle Indices ?

Database

Ans. Cassandra uses Hash Search which provides a look time of O(1) whereas Oracle Indices uses Binary Search that provide a lookup time of O(Log n).

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Q78. Difference between Normalization and Denormalization ?

Database

Ans. Normalization is the process of splitting one Table into multiple so as to avoid Data duplication whereas Denormalization is the process of reducing Tables that creates data duplication but would remove joins in the queries.

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Q79. Which of the two Normalization / Denormalization facilitate better performance ? Which of the two facilitate better space management ?

Database

Ans. DeNormalization facilitate better performance. Normalization remove data duplication and hence facilitate better database space management.

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Q80. Which of the following databases - Cassandra / Oracle - provides more flexibility about querying the database ?

Database

Ans. Oracle as it is not modeled for a particular query or set of queries.

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Q81. Which is the best NoSql Database for Performance ?

NoSql

Ans. Possible Answer - doument base - monogodb

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Q82. Design a Database Schema to store Employee Information with each employee having multiple addresses.

Database

Ans. We can have 2 entities i.e EMPLOYEE and ADDRESS and can have a relationship Table , EMPLOYEE_ADDRESS having one to may relationship between the two.

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Q83. Write a SQL to find 2nd Max value in a Table.

Database

Ans. SELECT MIN(FIELD) FROM (SELECT TOP 2 FIELD FROM TABLE ORDER BY FIELD DESC)

or

SELECT MAX(FIELD) FROM TABLE WHERE FIELD NOT IN (SELECT MAX(FIELD) FROM TABLE)

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Q84. What is read and write optimization in relation to databases ? Which database facilitates read optimization and which facilitates write optimization ?

Database

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Q85. Does relational database facilitate read or write optimization while storing information ?

database

Ans. Usually Relational Databases are optimized for writing. Some exception being usage of indices where indices needs to be updated after insertion and eventually helps with Log(n) reading time.

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Q86. How does relational database facilitates read optimization ?

Database

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Q87. What is difference between clustered and non clustered index?

Database

Ans. The clustered index determines how the data is stored in the rows of a table.The non-clustered index stores the data at a single place and the indexes are stored at another place.

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Q88. What is Left Outer Join ?

Database

Ans. It returns all the rows form the left table and matches the rows in both tables.

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Q89. How is RDBMS different from DBMS ?

Database

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Q90. Describe SQL Joins

Database

Ans. Oracle having following types of joins these are also called 8i joins. There are:

1. Equi (or) Inner join
2. Non Equi join
3.Self join
4.Outer join

Oracle also support the 9i (or) ANSI standard joins.There are:

1.Inner join
2.Left outer join
3.Right outer join
4.Full outer join
5.Natural join

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Q91. How do you fetch the records form database ?

Database

Ans. To fetch records from a database, you would use SELECT statements

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Q92. What are scrollable ResultSet?

Database

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Q93. What are the components of Data Warehousing ?

Database

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Q94. What are different in memory data structures that are used in No Sql Database ?

NoSql Database

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Q95. Design database schema for Facebook like application.

Database

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Library Management System has always been the favorite question. This questions is asked irrespective of level.

Q96. 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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Q97. 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

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Q98. 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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Q99. 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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Q100. Difference between indexing and partioning

Database

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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