How to convert a bigint to float - sql-server

Question

I know that a bigint should implicitly convert to a float but it does not seem to.
Table column to be updated:
[GBUsed] [float] NOT NULL,
Example of data in that column:
430.5
Logic: I'm summing 2 bigint columns together and dividing by 1024. An example of 1 of the row - I get: 1545
I the update the GBUsed column which is defined as float but it does not convert. I still get the 1545.
Stored procedure:
CREATE PROCEDURE [dbo].[RecalculateBandwidthUsage]
AS
BEGIN
SET NOCOUNT ON;
DECLARE #RowCount int,
#Rc int,
#Message varchar(max),
#CurrentDateTime datetime
CREATE TABLE #Temp
(
SwitchID int,
PortIndex int,
SwitchIP varchar(50),
GBUsed bigint
)
SET #CurrentDateTime = GETDATE()
-- FOR TESTING:
BEGIN TRANSACTION
INSERT #Temp (SwitchID, PortIndex, SwitchIP, GBUsed)
SELECT
c.SwitchID, c.PortIndex,
s.SwitchIP,
SUM ((c.BandwidthIn + c.BandwidthOut) / 1024) AS GBUsed -- converting to gigabytes
FROM
dbo.BandwidthLogCalculatedTest6 c
INNER JOIN
Switch s ON (c.SwitchID = s.SwitchID)
WHERE
(c.StartDate < DATEADD(HOUR, -1, #CurrentDateTime)
AND c.EntryType = 'Second')
GROUP BY
c.SwitchID, c.PortIndex, s.SwitchIP
ORDER BY
c.PortIndex
SELECT
#Rc = ##ERROR,
#RowCount = ##ROWCOUNT
IF #Rc <> 0
BEGIN
SELECT #Message = 'Critical Error - procedure RecalculateBandwidthUsage - on select. Return code: ' + Cast(#Rc as varchar)
RAISERROR (#Message, 16, 1)
END
-- FOR TESTING:
SELECT 'Temp table '
SELECT *
FROM #temp
ORDER BY PortIndex
IF #RowCount > 0
BEGIN
-- FOR TESTING:
SELECT 'Before update '
SELECT b.SwitchIP, b.SwitchPort, b.GBUsed
FROM dbo.Bandwidth b
INNER JOIN #temp t ON (b.SwitchIP = t.SwitchIP AND b.SwitchPort = t.PortIndex )
ORDER BY b.SwitchPort
-- Update.
UPDATE dbo.Bandwidth
SET GBUsed = CONVERT(float, t.Gbused)
FROM #Temp t
WHERE (Bandwidth.SwitchIP = t.SwitchIP AND Bandwidth.SwitchPort = t.PortIndex)
SELECT #Rc = ##ERROR
IF #Rc <> 0
BEGIN
SELECT #Message = 'Critical Error - procedure RecalculateBandwidthUsage - on Bandwidth update. Return code: ' + Cast(#Rc as varchar)
RAISERROR (#Message, 16, 1)
END
-- FOR TESTING:
SELECT 'After update '
SELECT b.SwitchIP, b.SwitchPort, b.GBUsed
FROM dbo.Bandwidth b
INNER JOIN #temp t ON (b.SwitchIP = t.SwitchIP AND b.SwitchPort = t.PortIndex)
ORDER BY b.SwitchPort
END
ROLLBACK TRANSACTION
END

Answer 1

You are doing an integer division - so therefore, your result will also be an integer (or BIGINT).
You need to use this code in order to get fractional values:
SUM ((c.BandwidthIn + c.BandwidthOut) / 1024.0) AS GBUsed
Dividing by 1024.0 (instead of just 1024) will make sure to use fractional values