Summary: in this tutorial, you will learn how to use the SQL Server INNER JOIN clause to query data from multiple tables. Introduction to SQL Server INNER JOIN. The inner join is one of the most commonly used joins in SQL Server. The inner join clause allows you to query data from two or more related tables.

1. Microsoft Sql Server Left Join Not Working
2. Ms Sql Server Left Outer Join Example
3. Microsoft Sql Server Left Join Syntax
4. Ms Sql Server Update Left Join

1. LEFT OUTER JOIN - All Parents, and their children if they have any. Right-clicking on the diamond in the middle of the Join line in the query designer reveals a context menu with some options for the JOIN. If we select 'Select All Rows from Parents', the left hand side of the diamond fills out, and some new SQL is generated.
2. Venn diagrams illustrate the difference in output rows for special cases of inner vs outer join.If no nulls or duplicate rows are input (so we can take a table to be a set of row-valued values & use normal math equality) then left & right circles hold output tables/sets of left & right join.
3. LEFT OUTER JOIN. Another type of join is called a SQL Server LEFT OUTER JOIN. This type of join returns all rows from the LEFT-hand table specified in the ON condition and only those rows from the other table where the joined fields are equal (join condition is met).

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

QuiverKG SosaKG Sosa

12 Answers

As per the documentation: FROM (Transact-SQL):

The keyword OUTER is marked as optional (enclosed in square brackets). In this specific case, whether you specify OUTER or not makes no difference. Note that while the other elements of the join clause is also marked as optional, leaving them out will make a difference.

For instance, the entire type-part of the JOIN clause is optional, in which case the default is INNER if you just specify JOIN. In other words, this is legal:

Here's a list of equivalent syntaxes:

Also take a look at the answer I left on this other SO question: SQL left join vs multiple tables on FROM line?.

WBTLasse Vågsæther KarlsenLasse Vågsæther Karlsen

To answer your question there is no difference between LEFT JOIN and LEFT OUTER JOIN, they are exactly same that said..

At the top level there are mainly 3 types of joins:

1. INNER
2. OUTER
3. CROSS

1. INNER JOIN - fetches data if present in both the tables.

2. OUTER JOIN are of 3 types:

   1. LEFT OUTER JOIN - fetches data if present in the left table.
   2. RIGHT OUTER JOIN - fetches data if present in the right table.
   3. FULL OUTER JOIN - fetches data if present in either of the two tables.

3. CROSS JOIN, as the name suggests, does [n X m] that joins everything to everything.
   Similar to scenario where we simply lists the tables for joining (in the FROM clause of the SELECT statement), using commas to separate them.

Points to be noted:

• If you just mention JOIN then by default it is a INNER JOIN.
• An OUTER join has to be LEFTRIGHTFULL you can not simply say OUTER JOIN.
• You can drop OUTER keyword and just say LEFT JOIN or RIGHT JOIN or FULL JOIN.

For those who want to visualise these in a better way, please go to this link:A Visual Explanation of SQL Joins

SriniVsactiwsactiw

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

Nothing. LEFT JOIN and LEFT OUTER JOIN are equivalent.

Mitch WheatMitch Wheat

I'm a PostgreSQL DBA, as far as I could understand the difference between outer or not outer joins difference is a topic that has considerable discussion all around the internet. Until today I never saw a difference between those two; So I went further and I try to find the difference between those. At the end I read the whole documentation about it and I found the answer for this,

So if you look on documentation (at least in PostgreSQL) you can find this phrase:

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In another words,

LEFT JOIN and LEFT OUTER JOIN ARE THE SAME

RIGHT JOIN and RIGHT OUTER JOIN ARE THE SAME

I hope it can be a contribute for those who are still trying to find the answer.

shA.t

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

Right Join and Right Outer Join

Results

xdhmooreWorkSmarterWorkSmarter

I find it easier to think of Joins in the following order:

• CROSS JOIN - a Cartesian product of both tables. ALL joins begin here
• INNER JOIN - a CROSS JOIN with a filter added.
• OUTER JOIN - an INNER JOIN with missing elements (from either LEFT or RIGHT table)added afterward.

Until I figured out this (relatively) simple model, JOINS were always a bit more of a black art. Now they make perfect sense.

Hope this helps more than it confuses.

Why are LEFT/RIGHT and LEFT OUTER/RIGHT OUTER the same? Let's explain why this vocabulary.Understand that LEFT and RIGHT joins are specific cases of the OUTER join, and therefore couldn't be anything else than OUTER LEFT/OUTER RIGHT. The OUTER join is also called FULL OUTER as opposed to LEFT and RIGHT joins that are PARTIAL results of the OUTER join. Indeed:

It is now clear why those operations have aliases, as well as it is clear only 3 cases exist: INNER, OUTER, CROSS. With two sub-cases for the OUTER.The vocabulary, the way teachers explain this, as well as some answers above, often make it looks like there are lots of different types of join. But it's actually very simple.

Yugo AmarylYugo Amaryl

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

Other equivalent syntaxes

Strongly Recommend Dotnet Mob Artice : Joins in Sql Server

MD. Khairul Basar

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 TableB)

• C) Outer join:

Hope it'd help.

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

sjngm

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

Uncle IrohUnslicedUnsliced

Just in the context of this question, I want to post the 2 'APPLY' operators as well:

JOINS:

1. INNER JOIN = JOIN

2. OUTER JOIN

   • LEFT OUTER JOIN = LEFT JOIN

   • RIGHT OUTER JOIN = RIGHT JOIN

   • FULL OUTER JOIN = FULL JOIN

3. CROSS JOIN

SELF-JOIN: This is not exactly a separate type of join. This is basically joining a table to itself using one of the above joins. But I felt it is worth mentioning in the context JOIN discussions as you will hear this term from many in the SQL Developer community.

APPLY:

1. CROSS APPLY -- Similar to INNER JOIN (But has added advantage of being able to compute something in the Right table for each row of the Left table and would return only the matching rows)
2. OUTER APPLY -- Similar to LEFT OUTER JOIN (But has added advantage of being able to compute something in the Right table for each row of the Left table and would return all the rows from the Left table irrespective of a match on the Right table)

I find APPLY operator very beneficial as they give better performance than having to do the same computation in a subquery. They are also replacement of many Analytical functions in older versions of SQL Server. That is why I believe that after being comfortable with JOINS, one SQL developer should try to learn the APPLY operators next.

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Microsoft Sql Server Left Join Not Working

Given the query below there might be multiple rows in dps_markers with the same marker key but we only want to join against the first. If I take this query and remove the top 1 and ORDER BY I get a value for mbg.marker_value but run as it is it always returns null

dstarhdstarh

4 Answers

Use OUTER APPLY instead of LEFT JOIN:

Unlike JOIN, APPLY allows you to reference the u.id inside the inner query.

Remus RusanuRemus Rusanu

The key to debugging situations like these is to run the subquery/inline view on its' own to see what the output is:

Running that, you would see that the profile_id value didn't match the u.id value of u162231993, which would explain why any mbg references would return null (thanks to the left join; you wouldn't get anything if it were an inner join).

You've coded yourself into a corner using TOP, because now you have to tweak the query if you want to run it for other users. A better approach would be:

With that, you can change the id value in the where clause to check records for any user in the system.

OMG Ponies

Ms Sql Server Left Outer Join Example

OMG Ponies

Because the TOP 1 from the ordered sub-query does not have profile_id = 'u162231993'Remove where u.id = 'u162231993' and see results then.

Run the sub-query separately to understand what's going on.

Damir SudarevicDamir Sudarevic

Damir is correct,

Your subquery needs to ensure that dps_user.id equals um.profile_id, otherwise it will grab the top row which might, but probably not equal your id of 'u162231993'

Your query should look like this:

Nathan Koop

Microsoft Sql Server Left Join Syntax

Nathan Koop

Ms Sql Server Update Left Join

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