Interview Questions Answers in MySQL, Core Java

What is DDL in MySQL?

Answer

In MySQL, DDL is the short form for Data Definition Language, which is used in database schemas and descriptions while deciding how data should reside in the database.

A list of DDL Queries:
 CREATE
 ALTER
 DROP
 TRUNCATE
 COMMENT
 RENAME

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Question { 1222 }

What is DML in MySQL?

Answer

DML is a short form for Data Manipulation Language which is used in data manipulation and mostly includes common SQL statements to store, modify, retrieve, delete and update data in a database.
The list of DML Queries:
 SELECT
 INSERT
 UPDATE
 DELETE
 MERGE
 CALL
 EXPLAIN PLAN
 LOCK TABLE

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Question { 1396 }

What is DCL in MySQL?

Answer

DCL is a short form for Data Control Language including commands which are concerned with User rights, permissions and other controls within the database system.

A list of queries for DCL:
 GRANT
 REVOKE

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Question { 1839 }

How to save images in MySQL?

Answer

Images in MySQL can be stored as blobs. For saving them: All the database images are converted into the blobs first. Then, they will get inserted into the database, and later on, it will get stored into the disk.

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Question { 1839 }

How to save images in MySQL?

Answer

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Question { 1199 }

Explain GRANT command in MySQL.

Answer

When a new MySQL user is created, it requires certain privileges to perform various database operations.
GRANT command grants certain privileges to the user.
For example below statement grants permission to run SELECT and INSERT on TABLE customertable to user username@localhost.
GRANT SELECT, INSERT ON customertable TO ‘username’@’localhost’

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Question { 1366 }

What are different TEXT data types in MySQL?

Answer

Different text data types in MySQL include:
• TINYTEXT,
• TEXT,
• MEDIUMTEXT and
• LONGTEXT.

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Question { 1480 }

What different Stored Objects are supported in MySQL?

Answer

Different stored objects in MySQL include VIEW, STORED PROCEDURE, STORED FUNCTION, TRIGGER, EVENT.
• VIEW - It is a virtual table based on a result set of a database query.
• STORED PROCEDURE - It is a procedure stored in database which can be called using CALL statement. Stored procedure does not return a value.

• STORED FUNCTION - It is like function calls which can contain logic. It returns a single value and can be called from another statement.
• TRIGGER - Trigger is program which is associated with a database table which can be invoked before or after insert, delete or update operations.
• EVENT - Event is used to run a program or set of commands at defined schedule.

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Question { 1386 }

What is MySQL Stored Procedure?

Answer

A procedure (often called a stored procedure) is a collection of pre-compiled SQL statements stored inside the database. It is a subroutine or a subprogram in the regular computing language.
A procedure always contains a name, parameter lists, and SQL statements.
We can invoke the procedures by using triggers, other procedures and applications such as Java,Python,PHP etc. It was first introduced in MySQL version 5. Now almost, it can be supported by almost all relational database systems.

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Question { 1260 }

What are the features of Stored Procedures in MYSQL?

Answer

 Stored Procedure increases the performance of the applications. Once stored procedures are created, they are compiled and stored in the database.
 Stored procedure reduces the traffic between application and database server. Because the application has to send only the stored procedure's name and parameters instead of sending multiple SQL statements.

 Stored procedures are reusable and transparent to any applications.
 A procedure is always secure. The database administrator can grant permissions to applications that access stored procedures in the database without giving any permission on the database tables.

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Question { 1276 }

In the below example, how many String Objects are created?
String s1="I am Java Expert";
String s2="I am C Expert";
String s3="I am Java Expert";

Answer

In the above example, two objects of Java.Lang.String class are created. s1 and s3 are references to same object

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Question { 1513 }

Explain Linked HashSet

Answer

Java LinkedHashSet class is a Linked list and Hash table implementation of the Set interface. It contains unique elements same as a HashSet. Linked HashSet in Java also provides optional set operations that can maintain the order of insertion.

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Question { 1372 }

List methods available in Java Queue interface

Answer

boolean add(object)
boolean offer(object)
object remove()
object poll()
object element()
object peek()

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Question { 1388 }

Explain Big-O notation with an example

Answer

The Big-O notation depicts the performance of an algorithm as the number of elements in ArrayList. A developer can use Big-O notation to choose the collection implementation. It is based on performance, time, and memory.
For example, ArrayList get(index i) is a method to perform a constant-time operation. It does not depend on the total number of elements available in the list. Therefore, the performance in Big-O notation is O(1).

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Question { 1439 }

What is the output of the following Java program?
class Main {
public static void main(String args[]){
final int i;
i = 10;
System.out.println(i);
}
}

10. What is the output of the following Java program?
class Main {
public static void main(String args[]){
final int i;
i = 10;
System.out.println(i);
}
}

Answer

Output
10
Since i is the blank final variable. It can be initialized only once. We have initialized it to Therefore, 10 will be printed.

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mahindhan