Difference between Group by and Having Clause With Example

Difference between Group by and Having Clause

Group By:

The GROUP BY clause will gather all of the rows together that contain data in the specified column(s) and will allow aggregate functions to be performed on the one or more columns.
Aggregate functions are like SUM,COUNT,MIN,MAX and AVG.

Example :

Consider the folowing table of Appriasal

Table Name : Appraisal

Emp_id	Amount
E01	2000
E02	4000
E03	5000
E02	6000
E01	2000

Query :

So if you want to get employee record who got total appraisal in one year then your query will be :
Select Emp_id, SUM(Amount)
from Appraisal
Group by Emp_id.

Result :

Emp_id	Amount
E01	4000
E02	10000
E03	5000

Having: The HAVING clause is used in combination with the GROUP BY clause. It can be used in a SELECT statement to filter the records that a GROUP BY returns.

Group functions cannot be used in where.To restrict row by group function having clause is used.

Example :

Consider the folowing table of Appriasal

Table Name : Appraisal

Emp_id	Amount
E01	2000
E02	4000
E03	5000
E02	6000
E01	2000

Query :

So Now if you want to get employee record who got total appraisal in one year more than 5000 then your query will be :
Select Emp_id, SUM(Amount)
from Appraisal
Group by Emp_id Having SUM(Amount)>5000.

Result :

Emp_id	Amount
E02	10000

Thanks :)

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