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

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Q301. How is RDBMS different from DBMS ?

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Q302. 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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Q303. What are the drawbacks of creating immutable objects ? Why don't we create all object immutable if mutability possesses so much threat ?

Core Java

Ans. Immutable objects relieves us from the problems of inconsistencies and security and helps with better read performance but at the same time are write performance and storage overheads. In case any modification is required , a new object is created and thus creating multiple copies of it.

This is the reason we use StringBuffer / StringBuilder when we have to append some text multiple times and then create a String out of it.

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Q304. Does immutability facilitates better performance ?

Core Java

Ans. Yes , but only the read performance in case we don't need to modify it much. In case we need to modify it a lot , it creates write performance overheads as we would need to create many news objects instead of just changing one.

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Q305. 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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Q306. What are scrollable ResultSet?

Database

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Q307. What are the components of Data Warehousing ?

Database

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Q308. What is the programming advantage of Immutability ?

Design

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Q309. What are the disadvantages of immutability ?

Design

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Q310. What are different in memory data structures that are used in No Sql Database ?

NoSql Database

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Q311. How are hash codes generated ?

Data Structure

Ans. Use hashCode() which returns an integer value, generated by a hashing algorithm

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Q312. Find Intersection/union between two arrays.

Core Java

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Q313. What is immutability and What are it's disadvantages ?

Design

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Q314. 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.

Q315. 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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Q316. 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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Q317. How to sort objects based on one of the field ?

Core Java

Ans. Using comparable and comparator and sorted collections like TreeSet or TreeMap.

or

use stream api from java 8 onwards which internally refers to comparable and comparator through lambda expressions

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Q318. 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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Q319. What is virtual table with respect to method overriding in Java ?

Core Java

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Q320. How is the virtual method table implemented in Java?

Core Java

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Q321. How many VTables are there for each class ?

Core Java

Ans. There is one VTable for each class.

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Q322. Can we declare an Interface with abstract keyword ?

Core Java

Ans. Yes

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Q323. Which jar files need to be included for using Hibernate ?

Hibernate

Ans. hibernate-orm
hibernate-validator
hibernate-ogm
hibernate-search

or you can download hibernate core with all dependencies.

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Q324. 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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Q325. Does Java SE has Immutable collections ?

Core Java

Ans. Yes wef from Java 9

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Q326. Isnt the use of HashTable and ConcurrentHashMap the same, i.e providing synchronized map collection ?

Core Java

Ans. Both provide the thread safety but the actual difference come when talk about performance. CHM gives best performance when no of writer threads are less in number.

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Q327. 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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Q328. Explain Hibernate caching mechanism

Hibernate

Ans. Every fresh session having its own cache memory, Caching is a mechanism for storing the loaded objects into cache memory. The advantage of cache mechanism is, whenever again we want to load the same object from the database then instead of hitting the database once again, it loads from the local cache memory only, so that the no. of round trips between an application and a database server got decreased. It means caching mechanism increases the performance of the application.

In hibernate we have two levels of caching

First Level Cache [ or ] Session Cache
Second Level Cache [ or ] Session Factory Cache [ or ] JVM Level Cache

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Q329. How would you securely migrate a database to RDS?

Amazon Web Services (AWS)

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Q330. What is the relationship between Base Class and Abstract Class ?

Core Java

Ans. Abstract Class is a class that's only allowed to be a Base class for it's usage. It can never be instantiated on it's own.

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