N/APosted on - 11/07/2011
In SQL, what is the difference between Group by and Order by statements? Also, I would like to know which statement to choose in a scenario where you need to count something? Can you please define the sub-query method used in Group by statement? ?
Difference between Group by and Order by statements
Group by used to set of values one or more value.
Order by sets vaues by sorting order.
The most general way to satisfy a GROUP BY clause is to
scan the whole table and create a new temporary table
ORDER BY [col1],[col2],…[coln];
If two rows will have the same value in col1 it will try to sort them according to col2 and so on.
GROUP BY [col1],[col2],…[coln]; Tells DBMS to group
(Aggregate) results with same value of column col1. You can
Use COUNT(col1), SUM(col1), AVG(col1) with it, sum all values or view average.
E.g. of Sub query of order by:
Select col_names from table_name
order by col_name
Thanking you. Hope this help you.