Deallocating Statement after executing both prepared Queries Gives desired Result.
SET prevDate=(CONCAT('details_',DATE_FORMAT(DATE_SUB(CURDATE(), INTERVAL 1
DAY),'%y%m%d')));
SET @qsql=CONCAT("SELECT COUNT(*) FROM ",prevDate," INTO @a");
PREPARE stmt FROM @qsql;
EXECUTE stmt;
SELECT @a AS detailcount ;
SET prevDate=(CONCAT('Subdetails_',DATE_FORMAT(DATE_SUB(CURDATE(),
INTERVAL 1 DAY),'%y%m%d')));
SET @qsql=CONCAT("SELECT COUNT(*) FROM ",prevDate," INTO @b");
PREPARE stmt FROM @qsql;
EXECUTE stmt;
SELECT @b AS Subdetails ;
DEALLOCATE PREPARE stmt;
SET totalcount=detailcount+Subdetails;
SELECT totalcount;