Concept Of SQL Server Part III

Concept Of SQL Server

Union :

  • Union is used to combine data of one or more tables.

  • Union only distinct values are allowed.

  • The following SQL statement returns the Id, FirstName, LastName (only distinct values) from both the "tblCustomer" and the "tblCustomerExpired" table :

Two Table :

tblCustomer

tblCustomerExpired

Example :

Union all :

  • Union all is used to combine data of one or more tables.

  • Union all duplicates values are allowed.

  • The following SQL statement returns the Id, FirstName, LastName (duplicate values also)from both the "tblCustomer" and the "tblCustomerExpired" table :

Two Table :

tblCustomer

tblCustomerExpired

Example :

Group By Clause :

  • Group by clause is used to combines the groups rows that have the same values into rows.

  • The Group By clause is used with aggregate functions (COUNT(), MAX(), MIN(), SUM(), AVG()) to group the result-set by one or more columns.

tblCustomer

Example :

SubQuery :

  • Subquery is nothing but query inside a query.

  • Inner query is called as subquery and embedded within the Where clause. 

In Keyword :

  • In keyword is used to retrieve rows in subquery based on the match of values given in a list.

Two Table :

tblAddress

tblCustomer

Example :

Correlated SubQuery :

  • Correlated Subquery is a subquery that uses values from the outer query.

Example :

Questions :

1) What are the Use of correlated Queries ?

  • Correlated subqueries are used for row-by-row processing. Each subquery is executed once for every row of the outer query.

  • A correlated subquery is evaluated once for each row processed by the parent statement. The parent statement can be a select statement.

2) What is the Difference between Inner join and Subquery ?

Inner join :

  • Inner join is used to combine rows from two or more tables.

  • Inner joins can be used to return rows. 

Subquery :

  • Subquery is used to combine data from different tables into a single result. 

  • Subqueries can be used to return either a single value or a row set.

Comments

Post a Comment

Popular posts from this blog

Basic Concept In C Sharp Day 16

Image
Lecture 16 : Basic Concept In C Sharp C Sharp : C#  (pronounced  see sharp , like the musical note C♯, but written with the number sign) is a general-purpose, multi-paradigm programming language encompassing static typing, strong typing, lexically scoped, imperative, declarative, functional, generic, object-oriented (class-based), and component-oriented programming disciplines. C# was developed around 2000 by Microsoft as part of its .NET initiative and later approved as an international standard by Ecma (ECMA-334) in 2002 and ISO (ISO/IEC 23270) in 2003. It was designed by Anders Hejlsberg, and its development team is currently led by Mads Torgersen, being one of the programming languages designed for the Common Language Infrastructure (CLI). The most recent version is 9.0, which was released in 2020 in .NET 5.0 and included in Visual Studio 2019 version 16.8. C-sharp musical note : " C sharp " was inspired by the musical notation whereby a sharp symb
Read more

VS Code In JavaScript Day 6

Image
Lecture 6 : VS Code In JavaScript What is VS Code : Visual Studio Code is a lightweight but powerful source code editor which runs on your desktop and is available for Windows, macOS and Linux. VS Code was announced on April 29,2015 by Microsoft at the 2015 Build conference. Why did we build VS Code : Visual Studio Code combines the simplicity of a source code editor with power developer tooling, like IntelliSense code completion and debugging. First and foremost, it is an editor that gets out of your way. The delightfully frictionless edit- build- bebug cycle means less time fiddling with your environment, and more time executing on your ideas. IntelliSense : IntelliSense is a general term for a variety of code editing features including : code completion, parameter information, quick information, and member list. IntelliSense features are sometimes called by other name such as "code completion", "content assist", and "code hinting".
Read more

ASP.NET MVC Interview Questions Part - II Day 26

Image
Lecture 26 : ASP.NET MVC Interview Questions Part - II 1) How is the URL structure of MVC core ? URL structure of MVC core is controller name with action name. Example : localhost:1234/{controller}/{action name}. The "localhost:1234" is considered as a controller name. 2) If the view name is different than action name how to invoke it  ? If the view name is different from action name we have to write and the view in double quotes. 3) How do we define navigation using anchor tag ? The HTML <a> element (also called the anchor element), containing its href attribute, creates a hyperlink to other web pages, locations within the same page, location to a specified title of another web page, or to an email web page.  The <a> tag defines a hyperlink, which is used to link from one page to another. The navigations can be defined using anchor tag as <a href="/Controller name/Action name"></a>. 4)  How to pass mode
Read more