Oracle-having condition filtering and where condition Filtering

Having is similar to where, and can be used to determine which record to choose.

Having determines the records to be displayed after grouping these records using group,

The difference is that the WHERE clause filters the result set before the group, while the having clause filters the result set after the group;

Having is an aggregate function, but where is not.

Here is an example:

Example: show the Department numbers and average salaries with an average salary greater than 2000

Select deptno, AVG (SAL) from EMP where AVG (SAL)> 2000 group by deptno;

Error,WhereThe grouping function is not allowed in the statement.HavingSolution

Select deptno, AVG (SAL) from EMP group by deptnoHavingAVG (SAL)> 2000;