Issue with comparing dates in SQL

Question

I have a table with the following columns

effective_start_date
effective_end_date
person_id

This is on Oracle DB.
I am writing a query to get me the person active for the current sysdate, using the following query.

select startDate, endDate, sysdate
from dateTable
where sysdate between startDate and endDate;

The issue is that this where clause never seems to get applied. The result contains rows that dont satisfy this condition. Any suggestions on what i might be missing.

Answer 1

Your query looks fine, and as APC suggests this is a common pattern. Which means you have a data problem. Displaying the full year will show why the unexpected records are matching, and any 'bad' dates - e.g. using unexpected centuries, which is not an unusual problem when dates are manipulated using a YY format mask:

select to_char(startDate, 'YYYY-MM-DD HH24:MI:SS') as startDate,
    to_char(endDate, 'YYYY-MM-DD HH24:MI:SS') as endDate, sysdate
from dateTable
where sysdate between startDate and endDate;

In the comments you've already noted that this showed dates from 4712, which showed as just 12 using your YY-MON-DD date format mask. I haven't seen exactly that, it's more common to see 0012 or 1912, but a record with endDate in 4712 certainly ends after sysdate. It's probably worth verify all of the dates in the table, not just those that were flagged by that where clause.