BETWEEN vs. = in SQL Server: What's the Difference?

Distinguishing BETWEEN from <= and >=<

In SQL Server 2000 and 2005, the BETWEEN operator and the combination of <= and >= operators in a WHERE clause present distinct functionalities.

The BETWEEN operator, as exemplified in Query 1, is a shorthand notation for specifying a range of values, including both the lower and upper bounds. This makes it a convenient option when searching for values between two specific dates, as in the example provided.

Alternatively, the combination of <= and >= operators, as seen in Query 2, specifies a range where only one end is inclusive. This approach is typically used when one or both endpoints should be excluded from the selection criteria. For instance, Query 2 would select events that occur on the dates 10/15/2009 through 10/17/2009, excluding those on 10/18/2009.

Considerations for DATETIME Values

When dealing with DATETIME values, however, the BETWEEN operator and the combination of <= and >= operators behave differently. With DATETIME, the comparison is based on the full date and time, including seconds. This means that Query 1, which specifies a range between '10/15/2009' and '10/18/2009', will return only events that occur before midnight on 10/18/2009, effectively excluding any events on that day.

To ensure accuracy when working with DATETIME, specify both the date and time during comparison. For instance, to capture all events on 10/18/2009, use a BETWEEN expression that specifies '10/18/2009 00:00' as the lower bound and '10/18/2009 23:59:59' as the upper bound.

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