Need to incorporate if else statement within my code - sql

Question

I am trying to achieve if else statement or case statement within my code below. I want to use one of these statement (if or case) to see if my RT_Ch_Pres_PX1 values are within certain min or max specs if they are above or below I want to say that if my RT_Ch_Pres_PX1 is below my min value by this much then display that value and indicate by how much is it of by and same this for exceeding max value. for example if my RT_Ch_Pres_PX1 value is 5 and I want to use my min valuse at 6 and max at 10. So my Rt_Ch_pres_px1 value is off by 1 so I would like to display this and say this value is of by 1 value. if RT_Ch_Pres_PX1 is within min and max values do nothing. Please see code below.
DECLARE #Result TABLE
(
RT_DateTime datetime,
RT_Phase_Name varchar(30),
RT_PhaseChangeCount int,
RT_Phase_Type int,
RT_Ch_Pres_PX1 float
);
/* Variables used to track changes to Phase Name */
DECLARE #RT_DateTime datetime;
DECLARE #RT_Phase_Name varchar(30);
DECLARE #RT_PhaseChangeCount int;
DECLARE #RT_Phase_Type int;
DECLARE #RT_Ch_Pres_PX1 float;
DECLARE #PhaseNameHold varchar(30);
DECLARE #PhaseChangeCount int;
SELECT #PhaseNameHold = ' ';
SELECT #PhaseChangeCount = 0;
SELECT #RT_PhaseChangeCount = 0;
/* Declare a cursor for determining when Phases change */
DECLARE ImportCursor CURSOR FAST_FORWARD FOR
SELECT
CONVERT(datetime, dbo.CycleData.Date_Time) as TimeConvert,
[dbo].[LookupPhases].[Phase_Name],
[dbo].[cycledata].[phase_type],
[dbo].[cycledata].[Ch_Pres_PX1]
FROM
CycleData INNER JOIN
CycleDataHeader ON CycleData.Unit_Number = CycleDataHeader.Unit_Number AND CycleData.Cycle_Counter_No = CycleDataHeader.Cycle_Counter_No INNER JOIN
LookupPhases ON CycleData.Phase_Type = LookupPhases.Phase_Type INNER JOIN
LookupEvent ON CycleData.Event_Type = LookupEvent.Event_Id LEFT OUTER JOIN
LookupAlarm ON CycleData.Alarm_Type = LookupAlarm.Alarm_Id
WHERE
[dbo].[CycleDataHeader].[Entered_Load_No1] = 'T14-0008'
ORDER BY
/* Appears to be the order that needs to be reported on */
Cycle_Time
-- dbo.CycleData.Unit_Number,
-- TimeConvert;
OPEN ImportCursor;
FETCH NEXT FROM ImportCursor INTO #RT_DateTime,
#RT_Phase_Name,
#RT_Phase_Type,
#RT_Ch_Pres_PX1
WHILE ##FETCH_STATUS = 0
BEGIN
IF (#RT_Phase_Name <> #PhaseNameHold)
BEGIN
SET #PhaseNameHold = #RT_Phase_Name;
SET #RT_PhaseChangeCount = #RT_PhaseChangeCount + 1;
END
INSERT INTO #Result VALUES(#RT_DateTime, #RT_Phase_Name,#RT_PhaseChangeCount,#RT_Phase_Type,#RT_Ch_Pres_PX1);
FETCH NEXT FROM ImportCursor INTO #RT_DateTime, #RT_Phase_Name,#RT_Phase_Type,#RT_Ch_Pres_PX1;
END
CLOSE ImportCursor;
DEALLOCATE ImportCursor;
SELECT
RT_DateTime,
RT_Phase_Name,
RT_PhaseChangeCount,
RT_Phase_Type,
RT_Ch_Pres_PX1
FROM #Result;

Answer 1

This case will generate the value you want:
case
when RT_Ch_Pres_PX1 < some_min then RT_Ch_Pres_PX1 - some_min
when RT_Ch_Pres_PX1 > some_max then RT_Ch_Pres_PX1 - some_max
else 0
end
The value created for the undershoot is negative (a good idea I think). If you want it to be positive, flip the calculation.