操作数类型冲突：date与dateadd中的int不兼容

Question

The following query works:

select dateadd(m, -5, getdate() - datepart(d, getdate()) + 1)

But when I tried to replace the getdate() with a specific date, example below:

select dateadd(m, -5, (convert(DATE,'2017-01-04') - (datepart(d, getdate()) + 1)))

I get the error saying Operand type clash: date is incompatible with int

What did I do wrong?

Answer 1

It is because GETDATE() returns DATETIME datatype ,You Can do -1 or +1 with Datetime values but not with Date values.

If you just changed your query a little bit , convert to datetime instead of Date it will work fine.

select dateadd(   m
               , -5
               , (convert(DATETIME,'2017-01-04') - (datepart(d, getdate()) + 1))) 

                              ^-- Datetime instead of Date