SQL Joins With Examples | Edureka

INTRODUCTION TO SQL
WHAT ARE JOINS IN SQL?
TYPES OF JOINS
FAQs ABOUT JOINS
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SQLisastandardlanguagewhichstandsforStructuredQueryLanguage.SQListhecoreofrelationaldatabaseandis
usedforaccessingandmanagingdatabase.
IntroductiontoSQL
Core of Relational
Databases
Database Administrators

JOINSinSQLarecommandswhichareusedtocombinerowsfromtwoormoretables,basedonarelatedcolumn
betweenthosetables. Theyarepredominantlyusedwhenauseristryingtoextractdatafromtableswhichhaveone-
to-manyormany-to-manyrelationshipsbetweenthem.
WhatareJoinsinSQL?

TYPES OF
JOINS
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INNER JOIN LEFT JOIN
RIGHT JOIN FULL JOIN

TYPES OF
JOINS
INNER JOIN
Thistypeofjoinreturnsthoserecordswhichhavematchingvaluesinboth
tables.So,ifyouperformanINNERJOINoperationbetweentheEmployeetable
andtheProjectstable,allthetupleswhichhavematchingvaluesinboththe
tableswillbegivenasoutput.
Syntax:
SELECT Table1.Column1,Table1.Column2,Table2.Column1,....
FROM Table1
INNER JOIN Table2
ON Table1.MatchingColumnName = Table2.MatchingColumnName;

TYPES OF
JOINS
LEFT JOIN
TheLEFTJOINortheLEFTOUTERJOIN returnsalltherecordsfromthelefttable
andalsothoserecordswhichsatisfyaconditionfromtherighttable.Also,for
therecordshavingnomatchingvaluesintherighttable,theoutputorthe
result-setwillcontaintheNULLvalues.
Syntax:
FROM Table1
LEFT JOIN Table2
SELECT Table1.Column1,Table1.Column2,Table2.Column1,.... FROM Table1 LEFT JOIN Table2 ON Table1.MatchingColumnName = Table2.MatchingColumnName;

TYPES OF
JOINS
RIGHT JOIN
TheRIGHTJOINortheRIGHTOUTERJOIN returnsalltherecordsfromtheright
tableandalsothoserecordswhichsatisfyaconditionfromthelefttable.Also,
fortherecordshavingnomatchingvaluesinthelefttable,theoutputorthe
result-setwillcontaintheNULLvalues.
Syntax:
FROM Table1
RIGHT JOIN Table2
SELECT Table1.Column1,Table1.Column2,Table2.Column1,.... FROM Table1 RIGHT JOIN Table2 ON Table1.MatchingColumnName = Table2.MatchingColumnName;

TYPES OF
JOINS
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FULL JOIN
FullJoinortheFullOuterJoinreturnsallthoserecordswhicheitherhavea
matchintheleft(Table1)ortheright(Table2)table.
Syntax:
FROM Table1
FULL JOIN Table2

What is a Natural Join and in which situations
is a Natural Join used?

What is a Natural Join and in which situations is a Natural
Join used?
Output when you apply
INNER JOIN
Output when you apply
NATURAL JOIN

How to map many-to-many relationships
using joins?

How to map many-to-many relationships using joins?
Projects Technologies Projects_to_Technologies
2JOIN statements

What is a Hash Join?

What is a Hash Join?
Hash Joins are also a type of joins which are used to join large tables or in an instance,
where the user wants most of the joined table rows.
The Hash Join algorithm is a two-step algorithm.
Build Phase Probe Phase

What is Self & Cross Join?

What is Self & Cross Join?
SELF JOIN in is a join of a table to itself. This implies that each row in a table is joined
with itself.
The CROSS JOIN is a type of join in which a join clause is applied to each row of a table to
every row of the other table. Also, when the WHERE condition is used, this type of JOIN
behaves as an INNER JOIN, and when the WHERE condition is not present, it behaves like a
CARTESIAN product..
Self Join
Cross Join

How to perform JOIN operation on three
tables?

How to perform JOIN operation on three tables?
To perform a JOIN operation on 3 tables, you
need to use 2 JOIN statements.

SQL Joins With Examples | Edureka

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