What is join in Linq?

Asked By: Ximei Gotschall | Last Updated: 26th January, 2020
Category: technology and computing databases
4.9/5 (144 Views . 42 Votes)
A LINQ JOIN keyword is used to combine rows from two or more tables, based on a common field between them. Like SQL Joins, the Linq is also provided some keywords to achieve Inner Join and Outer Join. As we know from SQL outer join is divided into 2 groups that is Left Outer Join and Right Outer Join.

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Also asked, can we use left join in Linq?

A left outer join is a join in which each element of the first collection is returned, regardless of whether it has any correlated elements in the second collection. You can use LINQ to perform a left outer join by calling the DefaultIfEmpty method on the results of a group join.

Additionally, what is include in Linq? If you want to have the object tree, you need to use Include because of lazy loading. INCLUDE - Specifies the related objects to include in the query results.

Subsequently, one may also ask, is Linq join inner or outer?

One commonly used feature of Language-Integrated Query (LINQ) is the facility to combine two sequences of related data using joins. The standard join operation provides an inner join but with a minor modification can be changed to give a left outer join.

What is DefaultIfEmpty in Linq?

The DefaultIfEmpty operator is used to replace an empty collection or sequence with a default valued singleton collection or sequence. Or in other words, it returns a collection or sequence with default values if the source is empty, otherwise return the source.

15 Related Question Answers Found

What is the difference between left join and left outer join?

In SQL, the left join returns all the records from first table and matched records from second table. If there is no match from second table then only records from first table are returned. Basically there is no difference in left join and left outer join. Left outer join also returns same results as left join.

What is left outer join?

About LEFT OUTER Join Operations. The result set of a LEFT OUTER join contains all rows from both tables that meet the WHERE clause criteria, same as an INNER join result set. Using a LEFT OUTER Join with the players table, we can select both rows from the teams table, along with any player rows that may exist.

What is Linq SQL?

What Is LINQ to SQL? LINQ to SQL is an O/RM (object relational mapping) implementation that ships in the . NET Framework "Orcas" release, and which allows you to model a relational database using . NET classes. You can then query the database using LINQ, as well as update/insert/delete data from it.

What is lazy loading in Linq?

Lazy Loading means the related entities are not loaded, until we iterate through them or bind them the data. By default, LINQ to SQL loads the related entities, using Lazy Loading. Employee entities are only loaded, when we iterate through the objects belonging to a given department.

What is lazy loading in Entity Framework?


Advertisements. Lazy loading is the process whereby an entity or collection of entities is automatically loaded from the database the first time that a property referring to the entity/entities is accessed. Lazy loading means delaying the loading of related data, until you specifically request for it.

How do I turn off lazy loading in Entity Framework?

To turn off lazy loading for a particular property, do not make it virtual. To turn off lazy loading for all entities in the context, set its configuration property to false.

Rules for lazy loading:
  1. context. Configuration.
  2. context. Configuration.
  3. Navigation property should be defined as public, virtual.

What is eager load?

Eager loading is the process whereby a query for one type of entity also loads related entities as part of the query. Eager loading is achieved by use of the Include method. For example, the queries below will load blogs and all the posts related to each blog.

Why we use include in Entity Framework?

Entity Framework When to Use Include
  • Lazy loading is the process whereby an entity or collection of entities is automatically loaded from the database.
  • Lazy loading is enabled by default in Entity Framework, and we can mark specific navigation properties or even whole entities as lazy by making them virtual.

What is object context?

ObjectContext is a class that manages all the database operations, like database connection, and manages various entities of the Entity Model. Database connection. It provides builtin Add, Update and Delete functions. Object Set of every entity. Provide State of pending changes.

What is way of loading data in Entity Framework?


Entity Framework - Eager Loading. Advertisements. Eager loading is the process whereby a query for one type of entity also loads related entities as part of the query. Eager loading is achieved by the use of the Include method. It means that requesting related data be returned along with query results from the database