Addition of total hours in SQL Server - sql

Question

In my database, I have a table with a column of type Float which represents the total work hours. I have to sum this value over all rows.
I can't use sum function, because 08.03 = 08 hour, 03 minute.
For example:
00.55 + 00.51=> 01.06
but I want
00.55 + 00.51 => 01.46
My query
Declare #TEMP1 table (TotalHours float)
insert into #TEMP1(TotalHours)
select ol.HrWork TotalHours
from OTLog ol
where EmployeeId = 2048
Declare #attCount int
Declare #attSum int
set #attSum = 0;
set #attCount = (select count(*) from #TEMP1)
print #attCount
while (#attCount <> 0)
begin
set #attSum = #attSum + (select Top 1 (LEFT(TotalHours,1)*60)+(RIGHT(TotalHours,2)) TotalHours from #TEMP1);
delete top(1) from #TEMP1;
set #attCount = #attCount - 1;
print #attSum;
end
print #attSum
select *
from OTLog
where EmployeeId = 2048
Any thoughts would be appreciated.

Answer 1

should use proper data type for storing time and not float
You need to break the float time into hour & minute. sum() it and convert back to your float format
select convert(int, total_minute / 60) + (total_minute % 60) / 100.0
from
(
select total_minute = sum(convert(int ,([hour] * 60) + [minute]))
from
(
select hour = floor(TotalHours), minute = convert(int, TotalHours * 100) % 100
from #TEMP1
) d
) d

Answer 2

You can try to use left(col1,2) to get hour number,right(col1,2) get minute number.
then use SUM to get totle hours and minutes in a subquery.
Then use DATEADD to add time value.
CREATE TABLE T(
col1 VARCHAR(10)
);
INSERT INTO T VALUES ('00.55');
INSERT INTO T VALUES ('00.51');
Query 1:
select FORMAT(DATEADD(minute,m,0)+ DATEADD(hour,h,0),'HH:mm:ss')
from (
SELECT SUM(CAST(left(col1,2) AS INT)) h ,SUM(CAST(right(col1,2) AS INT)) m
FROM T
) t1
Results:
| |
|----------|
| 01:46:00 |

Answer 3

Few issues with your problem:
first, float is not good choice for storing time information, look at date, time, datetime, timestamp, datetime2 - choose one of these, it will prevent such problems from occuring plus you have methods in SQL to work with such datatypes.
second - float is just approximation!, decimal stores exact values, you must be aware of that,
third - you need to be careful when dealing with decimal values in SQL Server, see Precision, scale, and Length (Transact-SQL) and this thread: Why is 199.96 - 0 = 200 in SQL?
After all, I can suggest this query to solve your problem:
select id,
sum(hours) + floor(sum(minutes) / 60) hours,
sum(minutes) % 60 minutes
from (
select id,
floor([time]) [hours],
cast([time] * 100 as int) % 100 [minutes]
from tblFloat
) a group by id
See this SQL fiddle, there you can test difference between using float and decimal (see the differences in a queries).