Technically, it's valid, but it's not very good.
Step 1 - store dates and times as dates and times, not
strings.
Step 2 - convert this string, "06/23/08 10:30 PM", to a
datetime variable using date functions.
Step 3 - adopt this style of writing sql.
where field_name
operator or keyword
value
In other words, instead of
where 1 = myfieldname
use
where myfieldname = 1
In your specific case, it would be
where sch_datetime_start >= some_value
and sch_datetime_end < some_value