Difference between WHERE and HAVING in SQL

1)  Apart from SELECT queries, you can use WHERE clause with UPDATE and DELETE clause but HAVING clause can only be used with SELECT query. For example following query, which involve WHERE clause will work but other which uses HAVING clause will not work :

update DEPARTMENT set DEPT_NAME="NewSales" WHERE DEPT_ID=1 ;  // works fine

update DEPARTMENT set DEPT_NAME="NewSales" HAVING DEPT_ID=1 ; // error

2) WHERE clause is used for filtering rows and it applies on each and every row, while HAVING clause is used to filter groups in SQL.

 
3) One syntax level difference between WHERE and HAVING clause is that, former is used before GROUP BY clause, while later is used after GROUP BY clause.



4) When WHERE and HAVING clause are used together in a SELECT query with aggregate function,  WHERE clause is applied first on individual rows and only rows which pass the condition is included for creating groups. Once group is created, HAVING clause is used to filter groups based upon condition specified.