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Q:

Explain Check constraint.

Answer

Oracle check constraint is used to ensure that before inserting the data in the database, it is validated and checked for the condition.
Example:
Below, the constraint is that the id has to be between 0 and 1000.
create table employee ( id number check (id between 0 and 1000), Name varchar(200) );

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Subject: Oracle

Q:

What are the types of constraints avaialable in oracle?

Answer

Oracle constraints are used to maintain consistent of data and ensure the data is properly maintained. A constraint is more or less a restriction we try to apply on a table.
Types of constraints:
- Check constraints
- NOT NULL constraint
- PRIMARY KEY constraint
- REFERENCES constraint
- UNIQUE constraint

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Subject: Oracle

Q:

How to Add a new column to an existing table?

Answer

New column can be added using the ALTER TABLE command as shown below:
Example:
ALTER TABLE employee ADD DateOfBirth date

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Subject: Oracle

Q:

Explain Row level and statement level trigger.

Answer

Row Level Trigger :
Row Level Trigger is fired each time row is affected by Insert, Update or Delete command. If statement doesn’t affect any row, no trigger action happens.

Statement Level Trigger :
This kind of trigger fires when a SQL statement affects the rows of the table. The trigger activates and performs its activity irrespective of number of rows affected due to SQL statement.

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Subject: Oracle

Q:

Explain the difference between trigger and stored procedure.

Answer

-  A stored procedure can accept parameters while a trigger cannot.
-  A trigger can’t return any value while stored procedures can.
-  A trigger is executed automatically on some event while a stored procedure needs to be explicitly called.
-  Triggers are used for insertions, update and deletions on tables while stored procedures are often using independently in the database.
-  A trigger cannot be written in a stored procedure. However, the reverse is not possible.

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Subject: Oracle

Q:

What are the varoius components of physical database structure of Oracle database?

Answer

Oracle database comprises of three kinds of files:
- Datafiles
- Redo log files
- Control files

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Subject: Oracle

Q:

List the various Oracle database objects.

Answer

- TABLES
- VIEWS
- INDEXES
- SYNONYMS
- SEQUENCES
- TABLESPACES

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Subject: Oracle

Q:

What do you understand by MapReduce?

Answer

MapReduce is a software framework that was created by Google. It`s prime focus was to aid in distributed computing, specifically large sets of data on a group of many computers. The frameworks took its inspiration from the map and reduce functions from functional programming.

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Subject: Cloud Computing