LEFT JOIN vs. LEFT OUTER JOIN in SQL Server

Question

What is the difference between LEFT JOIN and LEFT OUTER JOIN?

Answer 1

To answer your question

In Sql Server joins syntax OUTER is optional

It is mentioned in msdn article : https://msdn.microsoft.com/en-us/library/ms177634(v=sql.130).aspx

So following list shows join equivalent syntaxes with and without OUTER

LEFT OUTER JOIN => LEFT JOIN
RIGHT OUTER JOIN => RIGHT JOIN
FULL OUTER JOIN => FULL JOIN

Other equivalent syntaxes

INNER JOIN => JOIN
CROSS JOIN => ,

Strongly Recommend Dotnet Mob Artice : Joins in Sql Server

Answer 2

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

Nothing. LEFT JOIN and LEFT OUTER JOIN are equivalent.

Answer 3

There are only 3 joins:

• A) Cross Join = Cartesian (E.g: Table A, Table B)
• B) Inner Join = JOIN (E.g: Table A Join/Inner Join Table B)

• C) Outer join:

     There are three type of outer join
     1)  Left Outer Join     = Left Join
     2)  Right Outer Join    = Right Join
     3)  Full Outer Join     = Full Join    
  

Hope it'd help.

Answer 4

Syntactic sugar, makes it more obvious to the casual reader that the join isn't an inner one.

Answer 5

Left Join and Left Outer Join are one and the same. The former is the shorthand for the latter. The same can be said about the Right Join and Right Outer Join relationship. The demonstration will illustrate the equality. Working examples of each query have been provided via SQL Fiddle. This tool will allow for hands on manipulation of the query.

Given

Left Join and Left Outer Join

Results

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Right Join and Right Outer Join

Results

Answer 6

There are mainly three types of JOIN

1. Inner: fetches data, that are present in both tables
   • Only JOIN means INNER JOIN

2. Outer: are of three types

   • LEFT OUTER - - fetches data present only in left table & matching condition
   • RIGHT OUTER - - fetches data present only in right table & matching condition
   • FULL OUTER - - fetches data present any or both table
   • (LEFT or RIGHT or FULL) OUTER JOIN can be written w/o writing "OUTER"

3. Cross Join: joins everything to everything