If there is no range (just single dates), that's easy. Just count the rows: 

SELECT COUNT(*)
  FROM Company_relationship
 WHERE effective_date  = ?
    OR expiration_date = ?

[download]

If effective_date and expiration_date are begin and end dates, I bet you can do: 

SELECT COUNT(*)
  FROM Company_relationship
 WHERE effective_date <= ?
   AND expiration_date > ?

[download]

Both return one record with one field. If it's 0, proceed. Otherwise, you have an overlap.

In reply to Re: Overlapping dates Issue by ikegami
in thread Overlapping dates Issue by data67

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