Where we are using Where clause in SQL Server
In that you have 5 columns and 12 records. Now you want maximum salary employee details in the above table. So for that you can write a query as follow.
Select * from employee where salary= (Select Max (salary) from employee)
So in the above you are using a where clause.
On more query, where you can use Where clause.
Update employee set ename = ‘kvali’ where eid = 3
By the above query you can update employee name from ‘raj’ to ‘kvali’ where eid = 3
So in the above two cases you are using Where clause. On more important is you can’t use having clause for the above two queries.
We hope, by the above two sql queries you can get a idea where you can use “Where” clause.
Now we are using Having clause in SQL Server:We are using having clause for aggregate function output. Now we can write a query to get sum of salary of all departments individually.
Select dno, sum (salary) from employee group by dno
From the query we can get sum of salary of all departments individually, but if we want only department details which have more than 15000 salary. Then we are using “Having clause” clause.
Select dno, sum (salary) from employee group by dno having sum (salary) > 15000
Output for the above sql query is as in the following image
Important Note: In the above case we can’t use where Clause in the place of Having clause.
We hope from above two examples, you can clearly get the idea of difference between where clause and having clause.
Still, If you are not getting difference between where clause and Having clause I will give difference between where clause and Having clause in single sentence format. That is
“Where clause is used to filter table data and Having clause is used to filter aggregate data”. And one more difference is “Where clause can’t be used in Aggregate functions”
Some more important SQL Server topics:
SQL Query to Replace a character with Some other character in a column
SQL Query To Get Top 2 Highest Salary Employee Details In a SQL Server Table
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