Difference between JOIN and UNION in SQL

Pre-requisites: JOIN, UNION

JOIN in SQL is used to combine data from many tables based on a matched condition between them. The data combined using the JOIN statement results in new columns. Consider the two tables:

Boys

Girls

Example:

sql> SELECT Boys.Name, Boys.Age, Girls.Address,
     FROM Boys INNER JOIN Girls 
     ON Boys.Rollno = Girls.Rollno; 

The resultant table is: 

Name	Age	Address
Ritik	15	Delhi
Prakhar	17	Bhopal
Sanjay	16	Goa

UNION in SQL is used to combine the result set of two or more SELECT statements. The data combined using the UNION statement is into results into new distinct rows. 

Example:

sql> SELECT Name FROM Boys 
     WHERE Rollno < 16 
     UNION
     SELECT Name FROM Girls 
     WHERE Rollno > 9 

Output:

Name
Ram
Jayant
Rimi
Seema
Mona

Difference between JOIN and UNION in SQL 

JOIN	UNION
JOIN combines data from many tables based on a matched condition between them	SQL combines the result set of two or more SELECT statements.
It combines data into new columns.	It combines data into new rows
The number of columns selected from each table may not be the same.	The number of columns selected from each table should be the same.
Datatypes of corresponding columns selected from each table can be different.	The data types of corresponding columns selected from each table should be the same.
It may not return distinct columns.	It returns distinct rows.

My Personal Notes arrow_drop_up

Save