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

UNION:
UNION in SQL is used to combine the result-set of two or more SELECT statements. The data combined using 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 

The resultant table is:

Difference between JOIN and UNION in SQL :

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