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SQL is a standard language for accessing and manipulating databases.</div>
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<b>What is SQL?</b></div>
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SQL stands for Structured Query Language</div>
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SQL lets you access and manipulate databases</div>
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SQL is an ANSI (American National Standards Institute) standard</div>
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<b>Top 20 <span style="color: #6aa84f;">SQL Interview Questions and Answers</span></b><span style="color: #6aa84f;"> </span><span style="font-weight: normal;">for freshers and experienced are below are below:</span></h3>
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<b>1.       What is DBMS?</b><br />
Database Management System (DBMS)<br />
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<b>2.       What is RDBMS?</b><br />
Relational Database Management System (RDBMS)<br />
Example: SQL Server.<br />
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<b>3.       What is SQL?</b><br />
SQL (pronounced "ess-que-el") stands for <b>Structured Query Language</b>.<br />
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<b>4.       What is a Database?</b><br />
A database is an organized collection of data. The data is typically organized to model aspects of reality in a way that supports processes requiring information.<br />
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Example: School Management Database, Bank Management Database.<br />
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<b>5.       What is a primary key?</b><br />
The PRIMARY KEY constraint uniquely identifies each record in a database table.<br />
Primary keys must contain UNIQUE values.<br />
A primary key column cannot contain NULL values.<br />
Most tables should have a primary key, and each table can have only ONE primary key.<br />
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<b style="background-color: white; color: #333333; font-family: Verdana, Geneva, sans-serif; font-size: 12px; line-height: 19.2000007629395px;"><span style="color: #990000;">Also Read:</span> <a href="http://www.itechaleart.com/2014/04/top-50-common-interview-qa.html" style="color: #999999; text-decoration: none;"><span style="color: #3d85c6;">Top 50 Common Job Interview Questions and answers</span></a></b></div>
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<b>6.       What is a unique key?</b><br />
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The UNIQUE constraint uniquely identifies each record in a database table.<br />
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The UNIQUE and PRIMARY KEY constraints both provide a guarantee for uniqueness for a column or set of columns.<br />
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<b>7.       What is a foreign key?</b><br />
A foreign key is a column (or columns) that references a column (most often the primary key) of another table.<br />
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The purpose of the foreign key is to ensure referential integrity of the data. In other words, only values that are supposed to appear in the database are permitted.<br />
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<b>8.       What is a join?</b><br />
An SQL JOIN clause is used to combine rows from two or more tables, based on a common field between them.<br />
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<b>9.   What are the types of join?</b><br />
Inner join.<br />
Right Join.<br />
Left Join.<br />
Full Join.<br />
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<b>10.   What is normalization?</b><br />
Database normalization is the process of organizing the attributes and tables of a relational database to minimize data redundancy.<br />
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<b style="background-color: white; color: #777777; font-family: Verdana, Geneva, sans-serif; font-size: 12px; line-height: 24px;"><span style="color: #990000;">Also Read:</span> <a href="http://www.itechaleart.com/2014/04/seo-interview-qa.html" style="color: #999999; text-decoration: none;" target="_blank"><span style="color: #3d85c6;">Top 25 SEO Interview Questions and Answers</span></a></b></div>
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<b>11.   What is Denormalization.</b><br />
Denormalization is the process of attempting to optimize the read performance of a database by adding redundant data or by grouping data. In some cases, denormalization is a means of addressing performance or scalability in relational database software.<br />
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<b>12.   What are all the different normalizations?</b><br />
The normal forms can be divided into 5 forms, and they are explained below -.<br />
First Normal Form (1NF):.<br />
Second Normal Form (2NF):.<br />
Third Normal Form (3NF):.<br />
Fourth Normal Form (3NF):.<br />
Meeting all the requirements of third normal form and it should not have multi- valued dependencies.<br />
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<b>13.   What is a View?</b><br />
A view is a virtual table.<br />
This chapter shows how to create, update, and delete a view.<br />
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<b>15.   What is an Index?</b><br />
A database index is a data structure that improves the speed of data retrieval operations on a database table at the cost of additional writes and storage space to maintain the index data structure.<br />
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<div style="text-align: center;">
<b style="background-color: white; color: #333333; font-family: Verdana, Geneva, sans-serif; font-size: 12px; line-height: 19.2000007629395px;"><span style="color: #990000;">Also Read:</span> <a href="http://www.itechaleart.com/2015/02/android-interview-qa.html" style="color: #999999; text-decoration: none;" target="_blank"><span style="color: #3d85c6;">Top 20 Android Interview Questions And Answers</span></a></b></div>
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<b>16.   What are all the different types of indexes?</b><br />
There are three types of indexes -.<br />
Unique Index.<br />
Clustered Index.<br />
NonClustered Index.<br />
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<b>17.   What is a Cursor?</b><br />
 A cursor is the position indicator on a computer display screen where a user can enter text<br />
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<b>18.   What is a query?</b><br />
Queries are the primary mechanism for retrieving information from a database and consist of questions presented to the database in a predefined format.<br />
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<b>19.   What is subquery?</b><br />
A subquery is a query that is nested inside a SELECT, INSERT, UPDATE, or DELETE statement, or inside another subquery.<br />
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A subquery can be used anywhere an expression is allowed. In this example a subquery is used as a column expression named MaxUnitPrice in a SELECT statement.<br />
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<b>20.   What is a trigger?</b></div>
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Triggers are stored programs, which are automatically executed or fired when some events occur.<br />
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Triggers are, in fact, written to be executed in response to any of the following events:<br />
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<li>A database manipulation (DML) statement (DELETE, INSERT, or UPDATE).</li>
<li>A database definition (DDL) statement (CREATE, ALTER, or DROP).</li>
<li>A database operation (SERVERERROR, LOGON, LOGOFF, STARTUP, or SHUTDOWN).</li>
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<div style="text-align: center;">
<b style="background-color: white; color: #333333; font-family: Verdana, Geneva, sans-serif; font-size: 12px; line-height: 19.2000007629395px;"><span style="color: #990000;">Also Read:</span> <a href="http://www.itechaleart.com/2014/03/professional-blogging-resources.html" style="color: #999999; text-decoration: none;" target="_blank"><span style="color: #3d85c6;">Professional Blogging Resources for Power Blogging</span></a></b></div>
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<b>21.   What is Datawarehouse?</b><br />
Data warehouse (DW or DWH), also known as an enterprise data warehouse (EDW), is a system used for reporting and data analysis. DWs are central repositories of integrated data from one or more disparate sources.</div>
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Top 20 SQL Interview Questions and Answers

SQL is a standard language for accessing and manipulating databases. What is SQL? SQL stands for Structured Query Language SQL le...