Update data based on other column - sql

Question

I have a table and want to update a column based on other column of same table. Please look at below image for table design and table data.
In this tbl I want to update JoinDate as below steps.
1) if ModifiedDatetime is not null then ModifiedDatetime else CreatedDate.
2) Now if NextLevel is Hour then want to add hour of above date which we have in setp 1
3) Now if NextLevel is Day then want to add Day of above date which we have in setp 1
4) Now if NextLevel is Min then want to add Min of above date which we have in setp 1
5) Finally after completing all above process the date which I will get , I want to use to that data to update joindate.
I did this usig below cursor but I wnat to do this using sql update query.
DECLARE #EmpID INT
Declare #DtTm datetime
DECLARE #NextLevl INT
Declare #JoinDtTm datetime
DECLARE CurProg CURSOR FOR
select EmpID from tblEmp
OPEN CurProg
FETCH NEXT
FROM CurProg INTO #EmpID
WHILE ##FETCH_STATUS = 0
BEGIN
select #DtTm = case when ModifiedTime is null then CreatedDate else ModifiedTime end, #NextLevl = NextLevel from tblEmp where EmpID = #EmpID
if (#NextLevl = 'Min')
BEGIN
set #JoinDtTm = DATEADD(MI,1,#DtTm)
END
ELSE IF (#NextLevl= 'Hour')
BEGIN
set #JoinDtTm = DATEADD(HH,1,#DtTm)
END
ELSE
BEGIN
set #JoinDtTm = DATEADD(D,1,#DtTm)
END
--update tblEmp set JoinDtTm = #JoinDtTm where EMPId= #EMPId
FETCH NEXT
FROM CurProg INTO #EmpID
END
CLOSE CurProg
DEALLOCATE CurProg
Thanks,
Hitesh

Answer 1

Try this:
UPDATE TableName
SET JoinDate = CASE WHEN NextLevel = 'Hour' THEN DATEADD(HH,1,ISNULL(ModifiedDate,CreatedDate))
WHEN NextLevel = 'Day' THEN DATEADD(DD,1,ISNULL(ModifiedDate,CreatedDate))
WHEN NextLevel = 'Min' THEN DATEADD(MI,1,ISNULL(ModifiedDate,CreatedDate))
END

Answer 2

To do this without a cursor in an update statement then this should work
UPDATE TBL_EMP
SET JOINDATE =
(CASE WHEN MODIFIEDTIME IS NOT NULL
THEN (CASE WHEN NEXTLEVEL ='Hour' THEN dateadd(hh,1,modifiedtime)
ELSE (CASE WHEN NEXTLEVEL = 'Day' THEN dateadd(dd,1,MODIFIEDTIME)
ELSE(CASE WHEN NEXTLEVEL = 'Min' THEN dateadd(n,1,MODIFIEDTIME) ELSE MODIFIEDTIME END) END) END)
ELSE(CASE WHEN NEXTLEVEL ='Hour' THEN dateadd(hh,1,CREATEDDATE)
ELSE(CASE WHEN NEXTLEVEL = 'Day' THEN dateadd(dd,1,CREATEDDATE)
ELSE(CASE WHEN NEXTLEVEL = 'Min' THEN dateadd(n,1,CREATEDDATE) ELSE CREATEDDATE END) END) END) END)
FROM TBL_EMP

Answer 3

Drop your column joindate, it is redundant. Since joindate always rely on other columns in the same row, all you need is a computed column like this, otherwise you are stuck on constantly maintaining the values in joindate:
ALTER TABLE YourTable
ADD cJoindate as
CASE NextLevel
WHEN 'day' THEN DATEADD(D, 1, COALESCE(ModifiedDate,CreatedDate))
WHEN 'min' THEN DATEADD(MI, 1, COALESCE(ModifiedDate,CreatedDate))
WHEN 'hour' THEN DATEADD(HH, 1, COALESCE(ModifiedDate,CreatedDate))
END