[SOLVED] SQL : BETWEEN vs <= and >=

SQL : BETWEEN vs <= and >=

In SQL Server 2000 and 2005:

what is the difference between these two WHERE clauses?
which one I should use on which scenarios?

Query 1:

SELECT EventId, EventName
FROM EventMaster
WHERE EventDate BETWEEN '10/15/2009' AND '10/18/2009'

Query 2:

SELECT EventId, EventName
FROM EventMaster
WHERE EventDate >='10/15/2009'
  AND EventDate <='10/18/2009'

(Edit: the second Eventdate was originally missing, so the query was syntactically wrong)

Solution

They are identical: BETWEEN is a shorthand for the longer syntax in the question that includes both values (EventDate >= '10/15/2009' and EventDate <= '10/19/2009').

Use an alternative longer syntax where BETWEEN doesn't work because one or both of the values should not be included e.g.

Select EventId,EventName from EventMaster
where EventDate >= '10/15/2009' and EventDate < '10/19/2009'

(Note < rather than <= in second condition.)

Dealing with DATETIME

When dealing with DATETIME (vs. DATE) the result might not be intuitive however. If EventDate happens to be a DATETIME the comparison is done with the time (!)

EventDate BETWEEN '10/15/2009' AND '10/18/2009'

will in fact become:

EventDate BETWEEN '2009-10-15 00:00' and '2009-10-18 00:00'

as no time has specified. This will effectively exclude everything on 10/18/2009.

The proper expression in that case would be:

EventDate BETWEEN '2009-10-15 00:00' and '2009-10-18 23:59:59'