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

Understanding C Sharp Day 18

Image
Lecture 18 : Understanding C Sharp   Class Library : A class library  defines types and methods that are called by an application. The  Class Library .DLL  contains program code, data, and resources that can be can used by other programs and are easily implemented into other Visual Studio projects. Create New Class Library Project with Visual Studio :  Create New Project : Select C# in the language tab And then select  Class Library (.NET Framework) and press the NEXT button You can then proceed to give your project a Project Name Call the project  MathLibrary  (in order to copy/paste example code) Press the CREATE button, After you have given a name to your project Building the Class Library .DDL for C# : The following code example is a C# version of the Class Library.  The Class Library .DLL contains program code, data, and resources.  The Class Library in this example will feature a custom Math API that has a set of functions to Substract, Devide and Multiply numbers.
Read more

Concept In Angular Day 14

Image
Lecture 14 : Concept In Angular What is ngModel : ngModel is Angular’s answer to the two-way data binding problem. Previously in AngularJS, there was no way to perform a binding which would update automatically. What are Directives : Directives are markers on a DOM element that tell AngularJS to attach a specified behaviour to that DOM element or even transform the DOM element and its children. Angular includes various built-in directives. In addition to this, you can create custom directives for your application. ng-model Directive : The ng-model directive binds the value of HTML controls (input, select, textarea) to application data. With the ng-model directive you can bind the value of an input field to a variable created in AngularJS. Two-Way Binding : The binding goes both ways. If the user changes the value inside the input field. Two-way binding, we can display a data property as well as an update that property when the user makes changes. Two-way binding
Read more