Hour/Minutes Calculation Between Two Specific Date/Time & Converting Integer into varchar for Time Format

Select (DATEDIFF(MINUTE, OCLG1.StartDtTm , OCLG1.EndDtTm)) as 'Minutes' ,

((DATEDIFF(MINUTE, OCLG1.StartDtTm , OCLG1.EndDtTm))/(0.6*100)) as 'Hrs' ,

CASE when Durtype = 'M' then ((DATEDIFF(MINUTE, OCLG1.StartDtTm , OCLG1.EndDtTm))/(0.1*1000))

when Durtype = 'H' then ((DATEDIFF(MINUTE, OCLG1.StartDtTm , OCLG1.EndDtTm))/(0.6*100))

when Durtype = 'D' then ((DATEDIFF(MINUTE, OCLG1.StartDtTm , OCLG1.EndDtTm))/(0.6*100))

End 'TotalHrs.Mins',

OCLG1.DurType , OCLG1.ClgCode, OCLG1.parentId , OCLG1.CardCode , OCLG1.Recontact as 'BeginDate' , OCLG1.BeginTime,

CONVERT(datetime, CONVERT(varchar(10), OCLG1.Recontact, 120) + ' '

+ SUBSTRING(REPLICATE('0', 4 - LEN(OCLG1.BeginTime)) + CONVERT(varchar, OCLG1.BeginTime, 10), 1, 2) + ':'

+ SUBSTRING(REPLICATE('0', 4 - LEN(OCLG1.BeginTime)) + CONVERT(varchar, OCLG1.BeginTime, 10), 3, 4) + ':' + '00.000') as 'StartDtTm',

OCLG1.endDate , OCLG1.ENDTime ,

CONVERT(datetime, CONVERT(varchar(10), OCLG1.endDate, 120) + ' '

+ SUBSTRING(REPLICATE('0', 4 - LEN(OCLG1.ENDTime)) + CONVERT(varchar, OCLG1. ENDTime, 10), 1, 2) + ':'

+ SUBSTRING(REPLICATE('0', 4 - LEN(OCLG1.ENDTime)) + CONVERT(varchar, OCLG1. ENDTime, 10), 3, 4) + ':' + '00.000') as 'EndDtTm'

from OCLG1