# In SQL, what’s the difference between the having clause and the where clause?

The difference between the having and where clause is best illustrated by an example. Suppose we have a table called emp_bonus as shown below. Note that the table has multiple entries for employees A and B.

emp_bonus
 Employee Bonus A 1000 B 2000 A 500 C 700 B 1250

If we want to calculate the total bonus that each employee received, then we would write a SQL statement like this:

 ```select employee, sum(bonus) from emp_bonus group by employee; ```

## The Group By Clause

In the SQL statement above, you can see that we use the "group by" clause with the employee column. What the group by clause does is allow us to find the sum of the bonuses for each employee. Using the ‘group by’ in combination with the ‘sum(bonus)’ statement will give us the sum of all the bonuses for employees A, B, and C.

Running the SQL above would return this:

 Employee Sum(Bonus) A 1500 B 3250 C 700

Now, suppose we wanted to find the employees who received more than \$1,000 in bonuses for the year of 2007. You might think that we could write a query like this:

 ```BAD SQL: select employee, sum(bonus) from emp_bonus group by employee where sum(bonus) > 1000; ```

## The WHERE clause does not work with aggregates like SUM

The SQL above will not work, because the where clause doesn’t work with aggregates – like sum, avg, max, etc.. Instead, what we will need to use is the having clause. The having clause was added to sql just so we could compare aggregates to other values – just how the ‘where’ clause can be used with non-aggregates. Now, the correct sql will look like this:

 ```GOOD SQL: select employee, sum(bonus) from emp_bonus group by employee having sum(bonus) > 1000; ```

## Difference between having and where clause

So we can see that the difference between the having and where clause in sql is that the where clause can not be used with aggregates, but the having clause can. One way to think of it is that the having clause is an additional filter to the where clause.

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• Md Farooq

very clear explanation, keep it up Varoon

• Srinivas Reddy Dodla

Actually using “Having” will decrease your query performance when compare to the using “where” clause. Many times the by using having there will be a table scan done by the query, while WHERE use index’s, so the performance point where is a good option to use it.

• Vishnu Raj

Good Explanation

• Its good article for query writing..keep this blogging..

• sarvz

No, cant. both is same. wont work

• sravz

Excellent!. I have been searching the whole internet and you are the only person whjo gave an explanation instead of stating it doenst work

• Tabish Khan

Very well explained. I have a question regarding this.
In the “BAD SQL” example, instead of writing “where sum(bonus) > 1000;”, can we have an alias of “sum(bonus)” and write the query as:

select employee, sum(bonus) bonus from emp_bonus
group by employee where bonus > 1000;

• Sudha Parimala

Very Good explanation. Excellent

• goutham gonuguntla

sweet short and simple explanation

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• Jai Ganesh Jayaraman

Nice explanation.
Thanks

• Amod

Awesome explanation.

• Dolly

Very well explained !!
Thanks 🙂

• gnanasundaram mano

Okay….

• qin

Is there a way where we can use the functions in having but have a better efficiency?

• abhay

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• BHS

Great point !

• shweta

does using ‘ having ‘ increases the performance of the query better than the ‘where’ clause in sql queries and how? Please explain

• cromateu

this is nice..thanks a ton

• Ed

Very good explanation! A little addendum – a follow-up question might be: Is there a disadvantage to using HAVING, especially if there’s an equivalent query with WHERE?

The answer is: There could be performance issues. Queries with the HAVING statement need to filter the result set with O(n) (n being the number of records in the result set) for the HAVING expressions, while WHERE clauses can use indexes and other optimizations, making it possible to have O(log n) or even O(1) execution time complexity.

The reason for this is exactly the reason why HAVING exists in the first place: The DB generates the result set with the WHERE expression *before* the aggregate function is executed (so it can’t be evaluated *after* it). Since there can’t be indexes on result sets (they are dynamic, after all), a HAVING filter has to check each result row.

Hope it helps!

• DPJ

No, as the author said, you cannot use aggregate functions in WHERE clause. So the first query will not execute, guess you would get a syntax error there.

Thanks dude.. really helped a lot

• anna

thanks a lot ! good example !

• Sushil Kumar

thanks sir!

• brendan

It might be nice to show the different output of the queries. I assume it would look like this:

WHERE
EmployeeSum(Bonus)A1000B3250

HAVING
EmployeeSum(Bonus)A1500B3250

Is this a correct assumption?

• Qasim

Thank you very very much,
After studying from 5-6 sites I was still in confusion
but from here i clear my concept in only 5 minutes.

Thanks , excellent explanation.

• ashok

Good one bro

• Swapna

nicely explained.. thanku 🙂

• Avinash

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• robin

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• L

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• JK

Thanks boss… good explanation with the example…

• Sanaya Khan

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• mr

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• Vaibhav Tikoo

Awesome Description….Thanks

• varoon10

Thanks puhleez!

• varoon10

No prob Vasili!

• varoon10

Thanks Vimal!

• varoon10

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• parth

Well said

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• Vimal

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• noname

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• ROcky

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• dick

good example

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• vasili74

Thanks for the explanation..

• Uttam Barik

chicken. it is simple you can not use group function in where clause. it is not misleading

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• Venkatesh Dhanasekaran

Throughly Understand.. Thanks Dude 🙂

• puhleez

This is one of those basic concepts that I was having trouble wrapping my mind around. Excellent, simple example. Thanks!!!

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• Hiral

nice expaination