SQL Join creating duplication in output : <p>SO i Have a query which, due to my database requires a lot of tables to function. Unfortunately, this is an older database, which is a little problematic to navigate.</p>

<p>This query, originally checked whether a Membership was to be 40 or 50 years in length which was easily solved. However, Now I have to see whether a an attribute telling me whether they are reinstated members which would invalidate this timeline is present.</p>

<p>I have managed to get show and exclude records, but the the error I believe I have made, is in using an outer join as I was attempting to check multiple records in the joined table for this condition, which has lead several cases to duplication as multiple different attributes can be contained in the same column</p>

<p>I am just trying to make sense of this currently, but believe I have used the incorrect join because where an individual has a different attribute from this result it returns an additional record. </p>

<p>My question is which Join should I be using, or should in this instance I be looking at writing a sub query within the where condition</p>
