Error 1052 Field is Ambiguous using Inner Join Function
Qualify each column in the SELECT/WHERE and join clauses.

So, for example I've qualified the EventNo column so that it's read from the eventplan table in the SELECT clause - it's ambiguous because it is in both the eventplan and eventrequest tables.

SELECT eventplan.EventNo, DateAuth, COUNT(PlanNo)
FROM eventplan INNER JOIN eventrequest ON eventplan.eventNo = Eventrequest.EventNo
WHERE COUNT(PlanNo) &gt; 1 BETWEEN '2013-12-01' AND '2013-12-31';


You may nave to do the same for DateAuth and PlanNo if they exist in both tables (in this specific query).

It's good practice to always fully qualify column names - can make the query easier to read. You can always use a table alias too to cut down on typing.