What is the difference between StartDate > DateAdd(dd,-1,@EndDate) and StartDate >=@EndDate?

Question

What is the difference between this

StartDate > DateAdd(dd,-1,@EndDate)

and this

StartDate >=@EndDate

Answer 1

They are the same if StartDate and EndDate have a date data type.

If they a time component then the logic is different.

Consider:

EndDate    2017-05-09 11:00:00

Then the first gets everything after 2017-05-08 11:00:00.

The second gets everything on or after 2017-05-09 11:00:00. Clearly, these are different.

I should also add: When using date parts, spell out the full name of the date part. So use this:

StartDate > DateAdd(day, -1, @EndDate)

rather than using dd . This makes the code easier to read. It also prevent problems with abbreviations. Is mm for minutes or months? Is ms for milliseconds or microseconds? Why bother trying to remember?