Different types of joins with examples:


I will explain types of SQL JOINs in in this article. JOINs in SQL Server can be classified as follows:

• INNER JOIN
• LEFT OUTER JOIN
• RIGHT OUTER JOIN
• FULL OUTER JOIN
• CROSS JOIN

Each type is explained below with suitable examples:
Let’s consider two tables as Table1 & Table2 for our example.
– CREATE TEST TABLES
CREATE TABLE Table1(ID [int], Code [varchar](10));
GO
CREATE TABLE Table2(ID [int], Amount [int]);
GO

– INSERT DUMMY DATA
INSERT INTO Table1 VALUES
(1,’AAA’),(2,’BBB’),(3,’CCC’)
GO
INSERT INTO Table2 VALUES
(1,50),(2,30),(4,40)
GO

1_sql

INNER JOIN:


Inner joins return rows only when there is at least one row from both tables that matches the join condition. Inner joins eliminate the rows that do not match with a row from the other table. Below is the query for inner join:

SELECT *
FROM Table1 A
INNER JOIN Table2 B
ON A.ID = B.ID
GO

2_sql

LEFT OUTER JOIN
Left Outer joins return all rows from the left table referenced with a left outer join and matching rows from other table. Unmatched records will be NULL. Below is the query for Left Outer Join:

SELECT *
FROM Table1 A
LEFT OUTER JOIN Table2 B
ON A.ID = B.ID
GO

3_sql

RIGHT OUTER JOIN:


Right Outer joins return all rows from the right table referenced with a right outer join and matching rows from other table. Unmatched records will be NULL. Below is the query for Right Outer Join:

SELECT *
FROM Table1 A
RIGHT OUTER JOIN Table2 B
ON A.ID = B.ID
GO

4_sql

FULL OUTER JOIN:

Full Outer joins return all rows from both the tables. Unmatched records will be NULL. Below is the query for Full Outer Join:

SELECT * FROM Table1 A
FULL OUTER JOIN Table2 B
ON A.ID = B.ID
GO

6_sql

CROSS JOIN:

In cross joins, each row from first table joins with all the rows of another table. If there are m rows from Table1 and n rows from Table2 then result set of these tables will have m*n rows. Below is the query for

SELECT * FROM Table1 A
CROSS JOIN Table2 B
Go

7_sql

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