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Q: What are the types of join and explain each?(SQL)
There are various types of join which can be used to retrieve data and it depends on the relationship between tables.

Inner Join.
Inner join return rows when there is at least one match of rows between the tables.

Right Join.
Right join return rows which are common between the tables and all rows of Right hand side table. Simply, it returns all the rows from the right hand side table even though there are no matches in the left hand side table.

Left Join.
Left join return rows which are common between the tables and all rows of Left hand side table. Simply, it returns all the rows from Left hand side table even though there are no matches in the Right hand side table.

Full Join.
Full join return rows when there are matching rows in any one of the tables. This means, it returns all the rows from the left hand side table and all the rows from the right hand side table.

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Q: What is a query?
A DB query is a code written in order to get the information back from the database. Query can be designed in such a way that it matched with our expectation of the result set. Simply, a question to the Database.

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Q:- What is subquery?(SQL)
A subquery is a query within another query. The outer query is called as main query, and inner query is called subquery. SubQuery is always executed first, and the result of subquery is passed on to the main query.

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Q #1) Explain Web Services?

Answer: A Web Service can be defined as an application component for communication or say exchanging information between two applications over the network. Web services basically work on a client-server model where web services are easily accessible to client applications over the network.

To enable communication between various applications, web services take the help of open standards like XML (for data tagging), SOAP (for message transferring) and WSDL (to denote service availability).

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Q #2) What are the components of web service?

Answer: The different components of web services are as follows:

➡️SOAP- Simple Object Access Protocol
➡️UDDI- Universal Description, Discovery, and Integration
➡️WSDL- Web Service Description Language
➡️RDF- Resource Description Framework
➡️XML- Extensible Markup Language

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Q #3) Explain the term Interoperability with respect to Web services?

Answer: The term ‘Interoperability’ is widely used in product marketing description which defines the ability of different products or systems working together without any special effort from the customer part.


This is applicable in the same way when we talk about ‘Interoperability’ in terms of web services. Here, it determines the communication between various applications, sharing of data as well as services among themselves. There is no restriction on the type of application to be in communication.

If any code is written, it will be treated as a generic code that will be understood by all applications. Thus, the cost of writing specific codes for each application is reduced.

There is no restriction on the type of application to be in communication. If any code is written, it will be treated as a generic code that will be understood by all applications. Thus, the cost of writing specific codes for each application is reduced.

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Q #4) Define web service protocol stack and its layers?

Answer: Web service protocol stack consists of 4 layers. This can be described as follows:

a) Service transport: This is the first layer that helps in transporting XML messages between various client applications. This layer commonly uses the below-mentioned protocols:

HTTP(Hypertext Transport Protocol)
SMTP(Simple Mail Transport Protocol)
FTP(File Transfer Protocol)
BEEP(Block Extensible Exchange Protocol)
b) XML messaging: This layer is based on the XML model where messages are encoded in common XML format which is easily understood by others. This layer includes

XML-RPC
SOAP(Simple Object Access Protocol)
c) Service description: This layer contains descriptions like location, available functions, and data types for XML messaging which describes the public interface to a specific web service. This layer includes:

WSDL(Web Service Description Language)
d) Service discovery: This layer is responsible for providing a way to publish and find web services over the web. This layer includes:

UDDI(Universal Description, Discovery, and Integration)


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