Getting Error when Comparing Date in SQL Server - sql

Question

I want to compare DateTime field with input
Declare #Where varchar(MAX)
set #Where = #Where + 'EndDate >= ''' + cast('01-01-1970' as datetime) + ''' and EndDate <= ''' + cast('01-01-2200' as datetime) + ''''
print #Where
When I execute this Query I am getting error
Conversion failed when converting date and/or time from character
string.

Answer 1

This should be. You can't concatenate a string with a datetime .
Maybe try this.
Declare #Where varchar(MAX)
set #Where = #Where + 'EndDate >= ''' + cast(cast('01-01-1970' as datetime) as varchar) + ''' and EndDate <= ''' + cast(cast('01-01-2200' as datetime) as varchar) + ''''
print #Where
PS. You add the #Where variable, which is unseted (what means the value of #Where is NULL), to the constant values. And the result of adding NULL with something else is NULL.
maybe try this
Declare #Where varchar(MAX)
set #Where = 'EndDate >= ''' + cast(cast('01-01-1970' as datetime) as varchar) + ''' and EndDate <= ''' + cast(cast('01-01-2200' as datetime) as varchar) + ''''
print #Where

Answer 2

The main issue is, you are trying to concatenate string data with datetime data. Presumably, you want to produce the string
EndDate >= '01-01-1970' and EndDate <= '01-01-2200'
Within your current statement you have
+ cast('01-01-1970' as datetime)
+ cast('01-01-2200' as datetime)
This will take a date in string form and convert it to datetime datatype--which, internally, is an 8 byte binary value. You then try to concatenate that with a string, and SQL is unable to do that. To fix this, start with your string:
set #Where = 'EndDate >= ''' + cast('01-01-1970' as datetime) + ''' and EndDate <= ''' + cast('01-01-2200' as datetime) + ''''
remove the unnecessary cast statements:
set #Where = 'EndDate >= ''' + '01-01-1970'+ ''' and EndDate <= ''' + '01-01-2200' + ''''
which can further be simplified to:
set #Where = 'EndDate >= ''01-01-1970'' and EndDate <= ''01-01-2200'''
One other thing, you have
Declare #Where varchar(MAX)
Set #Where = #Where + <etc>
#Where is initialized as NULL, and when you concatenate (add) your configured string to it, the result will also be NULL. I’m guessing you are adding a clause to an existing WHERE statement; as this is a “new” clause, I’d recommend adding the appropriate boolean operator here, e.g.
Set #Where = #Where + ' AND ' + <etc>