MySQL Conditions from Multiple Rows - mysql

Question

I have been trying to calculate a table using a SELECT statement. I have a table like this:
--------------------------------------------------------------
AgentID | Date | Incurred | FallOffDate
==============================================================
kegomez | 2012-11-19 | 2.0 | 2013-11-19
kegomez | 2012-11-24 | 0.5 | 2013-11-24
kegomez | 2013-01-21 | 2.0 | 2014-01-21
kegomez | 2013-08-18 | 2.0 | 2014-08-18
I was trying to do the calculations on during the select and possibly create a view but have no luck so far. In the end the table will look like this.
--------------------------------------------------------------
AgentID | Date | Incurred | 90 | 180 | Total | FallOffDate
==============================================================
kegomez | 2012-11-19 | 2.0 | 2.0 | 2.0 | 2.0 | 2013-11-19
kegomez | 2012-11-24 | 0.5 | 0.5 | 0.5 | 2.5 | 2013-11-24
kegomez | 2013-01-21 | 2.0 | 1.0 | 0.0 | 2.5 | 2014-01-21
kegomez | 2013-08-18 | 2.0 | 2.0 | 2.0 | 4.5 | 2014-08-18
The total column uses values from the previous row to calculate its values. For example the date in row 4 will need to reference the date in row 3 to see if the date is greater. Would I need to try this with a subquery? How this will eventually work is that every 90 days up to 180 days the agent will loose 1 point if no more are incurred. Thus the reason why I need to reference other rows. If it helps this data is currently in Excel but is getting too large to manage and we need to move it over to something that performs better.
SELECT AgentID, Date, Incurred,
#90 := IF(Date<=CURDATE()-90 AND #r=0, Incurred-1.0, IF(Difference>90, Incurred-1, Incurred)) AS 90Day,
#180 := IF(Date<=CURDATE()-90 AND #r=0, Incurred-1.0, IF(Difference>180, Incurred-2, #90)) AS 180Day,
#Total := IF(#180<0,0,IF(FallOffDate<=CURDATE(),0, #180)) AS Total,
FallOffDate
FROM (SELECT mo.AgentID, mo.Incurred, FallOffDate,
#r AS LEAD_date,
DATEDIFF(#r,Date) AS Difference,
(#r := Date) AS Date
FROM (
SELECT m.*
FROM (
SELECT #_date = NULL
) VARIABLE,
attendance m
ORDER BY
AgentID, Date DESC
) mo
WHERE (CASE WHEN #_date IS NULL OR #_date <> date THEN #r := NULL ELSE NULL END IS NULL)
AND (#_date := date) IS NOT NULL) T
ORDER BY AgentID, Date;

Answer 1

Yes, you need to do this with a subquery, try with something like this (if you want the 4th row to access the date in 3rd row):
SELECT mo.AgentID, mo.date,
#r AS 'LAG(date)',
(case when #r<Date then 'YES' when #r is null then 'IS NULL' else 'NO' end) 'Is Bigger',
(#r := Date) AS Date
FROM (
SELECT m.*
FROM (
SELECT #_date = NULL
) variable,
data m
ORDER BY
AgentID
) mo
WHERE (CASE WHEN #_date IS NULL OR #_date <> date THEN #r := NULL ELSE NULL END IS NULL)
AND (#_date := date) IS NOT NULL
You can see a working demo here
Or you can try this query if you want that 3rd row has access to date in 4th row
SELECT AgentID,date,LEAD_date,concat(Difference,' days') FROM
(SELECT mo.AgentID,
#r AS LEAD_date,
DATEDIFF(#r,Date) as Difference,
(#r := Date) AS Date
FROM (
SELECT m.*
FROM (
SELECT #_date = NULL
) variable,
data m
ORDER BY
AgentID,date desc
) mo
WHERE (CASE WHEN #_date IS NULL OR #_date <> date THEN #r := NULL ELSE NULL END IS NULL)
AND (#_date := date) IS NOT NULL) T
order by AgentID,date;
You can see a working demo here