Error converting nvarchar to float in SQL Server - sql-server

Question

I want to view the session hours of previous 3 months in my SQL (hrs column is declared as nvarchar), I need to convert the data into float if I want to view the data of last 3 months but I am getting some errors
SELECT sum(convert(float, hrs))
FROM companysonvinunitvenue
WHERE date >= DATEADD(day, -90, GETDATE())
Error:
Msg 8114, Level 16, State 5, Line 1
Error converting data type nvarchar to float.
SELECT sum(cast(hrs as float))
FROM companysonvinunitvenue
WHERE date >= DATEADD(day, -90, GETDATE())
Error:
Msg 8114, Level 16, State 5, Line 1
Error converting data type nvarchar to float.
SELECT CAST(CAST (hrs AS NUMERIC(19,4)) AS INT)
FROM companysonvinunitvenue
WHERE date >= DATEADD(day, -90, GETDATE())
Error:
Msg 8114, Level 16, State 5, Line 1
Error converting data type nvarchar to numeric.
SELECT CAST(CAST (hrs AS int) AS INT)
FROM companysonvinunitvenue
WHERE date >= DATEADD(day, -90, GETDATE())
Error:
Msg 245, Level 16, State 1, Line 1
Conversion failed when converting the nvarchar value '02:00:00 ' to data type int.
I tried these four ways and failed in all of them, how I need to do this?

Answer 1

First, use date and time data types for datetime values. And you will avoid these and many other troubles and also save disk space, RAM, reduce number of reads and so on.
As for your problem. For Sql Server 2008+
DECLARE #companysonvinunitvenue TABLE (hrs NVARCHAR(10))
INSERT #companysonvinunitvenue VALUES ('02:00:00'),('21:31:03')
SELECT DATEPART(HOUR,CAST(hrs AS time))
FROM #companysonvinunitvenue
For other versions
DECLARE #companysonvinunitvenue TABLE (hrs NVARCHAR(10))
INSERT #companysonvinunitvenue VALUES ('02:00:00'),('21:31:03')
SELECT cast(LEFT(hrs,2) AS INT)
FROM #companysonvinunitvenue