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Advanced level question frequently asked in US based companies. Recently asked in EMC and Intuit.
  Q31. Can you provide some implementation of a Dictionary having large number of words ? Solution
Ans. Simplest implementation we can have is a List wherein we can place ordered words and hence can perform Binary Search.

Other implementation with better search performance is to use HashMap with key as first character of the word and value as a LinkedList.

Further level up, we can have linked Hashmaps like ,

hashmap {
a ( key ) -> hashmap (key-aa , value (hashmap(key-aaa,value)
b ( key ) -> hashmap (key-ba , value (hashmap(key-baa,value)
....................................................................................
z( key ) -> hashmap (key-za , value (hashmap(key-zaa,value)
}

upto n levels ( where n is the average size of the word in dictionary.

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   Like         Discuss         Correct / Improve     java   collections   hashmap   binary search   search algorithm   advanced   architecture   data structure     Asked in 6 Companies        frequent
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 Q32. Which of the following syntax is correct ?import static java.lang.System.*;or static import java.lang.System.*;Core Java
Ans. import static java.lang.System.*;

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   Like         Discuss         Correct / Improve     java   static import   generics   import   OCJP   SCJP   Oracle certified java developer     Asked in 1 Companies

Very frequently asked if being interviewed for hibernate. Frequently asked in Tata Consultancy (TCS) and Overstock.com
  Q33. Difference between load and get ?Hibernate
Ans. If id doesnt exist in the DB load throws an exception whereas get returns null in that case.get makes the call to DB immediately whereas load makes the call to proxy.

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   Like         Discuss         Correct / Improve     hibernate     Asked in 16 Companies      basic        frequent

Frequently asked question in companies using Hibernate.
  Q34. What is Lazy Initialization in Hibernate ?Hibernate
Ans. It's a feature to lazily initialize dependencies , relationship and associations from the Database. Any related references marked as @OneToMany or @ManyToMany are loaded lazily i.e when they are accessed and not when the parent is loaded.

  Sample Code for Lazy Initialization

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   Like         Discuss         Correct / Improve     hibernate   lazy loading hibernate   lazy initialization hibernate   architecture     Asked in 77 Companies      Basic        frequent
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 Q35. What things you will look for if you get following exception while making DB call ?

table or view does not exist		Database
Ans. First will check if the table or view actually exist in the DB

If it does , Will make sure to see that the application has rights on the schema that holds the respective Table.

Will then make sure that we have prefixed the schema with the table name while accessing it.

Will then make sure that its not DB Cache that's causing it as the table DDL might have been created recently.

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   Like         Discuss         Correct / Improve     sql   database   oracle   technical lead

 Q36. What's the benefit for specifying constraints like Not Null , Primary Key explicitly instead of specifying it against the column ?Database
Ans. In case we specify them explicitly we can have control over constraint name as otherwise they will be system generated. It provides an ease in case we plan to drop the constraint in future.

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   Like         Discuss         Correct / Improve     sql   database   oracle

 Q37. How can we disable a constraint ?Database
Ans. alter table
table_name
DISABLE constraint
constraint_name;

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   Like         Discuss         Correct / Improve     sql   database   oracle

 Q38. Can we have foreign key reference to a non primary key column ?Database
Ans. Yes, but the respective key in the foreign table should be declared Unique.

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   Like         Discuss         Correct / Improve     sql   database   oracle     Asked in 2 Companies

 Q39. What should be done for auto generating primary key id in a table ?Database
Ans. We need to create a sequence.

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   Like         Discuss         Correct / Improve     sql   database   oracle

 Q40. Which constraint cannot be specified as an explicit constraint and should be specified with the column only ?Database
Ans. NOT NULL

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   Like         Discuss         Correct / Improve     sql   oracle   database   ddl   constraint   table creation

 Q41. How to know the structure of a Table in Oracle ?Database
Ans. DESC

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   Like         Discuss         Correct / Improve     sql   database   oracle

 Q42. How to know the constraints on a Table in Oracle ?Database
Ans. SELECT *
FROM user_constraints
WHERE table_name = ''

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   Like         Discuss         Correct / Improve     sql   database   oracle

 Q43. How to know the default column value of a Table in Oracle ?Database
Ans. Select DATA_DEFAULT
from DBA_TAB_COLUMNS
where TABLE_NAME = '' and COLUMN_NAME='';

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   Like         Discuss         Correct / Improve     sql   database   oracle

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