SQL Group By/ Having

GROUP BY
SELECT SUM(m1) FROM tbl3;
SELECT SUM(m1) FROM tbl3 GROUP BY sno;
SELECT SUM(m1) as Sum_Of_m1 FROM tbl3 GROUP BY sno;
SELECT sno,SUM(m1),avg(m1) FROM tbl3 GROUP BY sno;
SELECT m1,SUM(m1) FROM tbl3 GROUP BY sno;/*invalid*/

HAVING... was added to SQL because the WHERE keyword could not be used against aggregate functions (like SUM), and without HAVING... it would be impossible to test for result conditions.

SELECT column,SUM(column) FROM table GROUP BY column HAVING SUM(column) condition value

SELECT SUM(m1) FROM tbl3 where m1>10;

SELECT SUM(m1) FROM tbl3 where SUM(m1)>10;/*invalid*/

SELECT sno,SUM(m1) FROM tbl3 GROUP BY sno HAVING m1>10;/*invalid*/

SELECT sno,SUM(m1) FROM tbl3 GROUP BY sno HAVING SUM(m1)>10;