Cross join

In this lesson we are going to study about Corss joins in a database.
Cross Join  or Cartesian Product:

• Each row from the first table is combined with the each rows from the second table.
• Rows in the result table is the product of rows in each table.
• For large no of rows ,it takes longer time.
• It does not include any join condition .
• A Cross Join B Result table as  A*B.

Example1:In the below diagram we are having two table's Table:A,Table:B .Table:A is having one column X

with three data and Table:B is having one column Y with two data.So the value of  m=3 and n=2.
So when we are doing cross join of Table:A with Table:B this will return a table which have
m*n =3*2
       =6(Record)
i.e each row of one table is mapped with each row of second table.




Example2:  In the below diagram we are having two table's Table:R,Table:S .Table:A is having Two column A,column B

with three data and Table:S is having two column B.column C with two data.So the value of  m=3 and n=2.
So when we are doing cross join of Table:A with Table:B this will return a table which have
m*n =3*2
       =6(Record)
NOTE: Result table is having all columns of Table:R,Table:S

Syntax:
Explicit cross join:

SELECT *

FROM Table1
CROSS JOIN Table2



Implicit cross join:

SELECT *
FROM  Table1 , Table2;

just have a look on below video and try to Cross Join table by your self and you can download the sql scrpit used in this video from here DOWNLOAD LINK

 Related Article

• Join
• Equi Join
• Non  Equi Join
• Self Join 
• Natural Join  
• Join with Using clause.
• Join with ON clause
• Outer Join.  

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