MySQL - Select new entries only for every day - mysql

Question

I'm trying to find the new tasks assigned to employees per day. The fiddle is here
An employee may cycle between say 4 tasks A,B,C & D. On 1st Jan, he may get assigned task 'A', on 2nd Jan he may get assigned task 'B', 5th Jan task 'C', 6th Jan task 'D' & say on Jan 14th he gets assigned task 'A' again. I'd like to see the date & the newly assigned task compared to the previous day with respect to any particular day.
The output of the SQL I need should show me only the new task he is assigned on a given day. The definition of new is with respect to the previous day or the last present entry if data is not present for a given date.
Here's how it should ideally look -
UPDATED SQL
FIDDLE HERE
SELECT task_date,
employee_name,
Group_concat(task_name)
FROM (
SELECT DISTINCT a.task_date,
a.employee_name,
CASE
WHEN b.employee_name IS NOT NULL
AND c.employee_name IS NULL THEN NULL
ELSE a.task_name
END AS task_name
FROM forgerock AS a
LEFT OUTER JOIN forgerock AS b
ON a.employee_name = b.employee_name = 'A'
AND a.task_date >= '2015-01-02'
AND a.task_date <= '2015-01-04'
AND b.task_date >= '2015-01-02'
AND b.task_date <= '2015-01-04'
AND a.task_date - 1 = b.task_date
AND a.region = b.region = 'USA'
LEFT OUTER JOIN forgerock AS c
ON a.employee_name = c.employee_name = 'A'
AND a.task_date >= '2015-01-02'
AND a.task_date <= '2015-01-04'
AND c.task_date >= '2015-01-02'
AND c.task_date <= '2015-01-04'
AND a.task_date - 1 = c.task_date
AND a.task_name <> c.task_name
AND a.region = b.region = 'USA'
ORDER BY a.task_date,
a.employee_name,
a.task_name) AS temp
GROUP BY task_date,
employee_name

Answer 1

select task_date,employee_name,GROUP_CONCAT(task_name) from(
select distinct a.task_date,a.employee_name
,case when b.employee_name is not null and c.employee_name is null
then null
else a.task_name end as task_name
from ForgeRock as a left outer join ForgeRock as b
on a.employee_name = b.employee_name and a.task_date-1 = b.task_date
left outer join ForgeRock as c
on a.employee_name = c.employee_name and a.task_date-1 = c.task_date
and a.task_name <> c.task_name
order by a.task_date,a.employee_name,a.task_name) as temp
group by task_date,employee_name
Adding Condition :
select task_date,employee_name,GROUP_CONCAT(task_name) from(
select distinct a.task_date,a.employee_name
,case when b.employee_name is not null and c.employee_name is null
then null
else a.task_name end as task_name
from ForgeRock as a left outer join ForgeRock as b
on a.employee_name = b.employee_name and a.task_date-1 = b.task_date and a.task_date between '2015-01-02' AND '2015-01-04' and b.task_date between '2015-01-02' AND '2015-01-04'
left outer join ForgeRock as c
on a.employee_name = c.employee_name and a.task_date-1 = c.task_date and a.task_date between '2015-01-02' AND '2015-01-04' and c.task_date between '2015-01-02' AND '2015-01-04'
and a.task_name <> c.task_name
where a.region = 'USA' and a.task_date between '2015-01-02' AND '2015-01-04'
order by a.task_date,a.employee_name,a.task_name) as temp
group by task_date,employee_name