Sql Query not working?

Try wrapping it in a subselect, then making the comparison on YR2 afterwards in the outer query:

SELECT a.* FROM ( SELECT country_code, SUM(attendance) AS k6_attendance, COUNT(*) AS total_events, IF(MONTH(session_date)<5,YEAR(session_date),YEAR(session_date)+1) AS YR2 FROM v_knowledge_session v WHERE session_date > 0 AND country_code = 'IN' GROUP BY YR2, country_code ) a WHERE a.YR2 > YEAR(NOW())-2 ORDER BY a.country_code, a.YR2 

You need to use the same expression in places other than ORDER BY clause

SELECT country_code,SUM(`attendance`) as k6_attendance,count(*) as total_events , IF(MONTH(`session_date`)<5,YEAR(`session_date`),YEAR(`session_date`)+1) as YR2 FROM `v_knowledge_session` v WHERE session_date >0 Group by IF(MONTH(`session_date`)<5,YEAR(`session_date`),YEAR(`session_date`)+1) ,country_code HAVING IF(MONTH(`session_date`)<5,YEAR(`session_date`),YEAR(`session_date`)+1) >(YEAR(NOW())-2) AND country_code='IN' ORDER BY country_code,YR2; 

You can't use non-aggregated condition in HAVING clause. country_code='IN' must be in the WHERE clause. The reason why HAVING clause was created is because the WHERE clause cannot handle aggregated condition. In your query, having clause is not needed because your condition is not aggregated. Also you can remove the ALIAS v

try this one:

SELECT country_code, SUM(`attendance`) as k6_attendance, count(*) as total_events , IF(MONTH(`session_date`) < 5 , YEAR(`session_date`), YEAR(`session_date`) + 1) as YR2 FROM `v_knowledge_session` WHERE session_date > 0 AND country_code='IN' AND YR2 > (YEAR(NOW())-2) Group by YR2, country_code ORDER BY country_code,YR2;