Short answer: Different excel files
I'm starting to think I have two problems...
I have about 50 excel files, from each file I'm loading 3 tables (in this case called t1,t2 and t3).
t1 has fields: ID, Date, Time, Place, Weather
t2 has fields: ID, Date, Time, Organisation,
t3 has fields: ID, Date, Time, Place, Member1, Member2....Member10
Problem 1: Not all memberfields exits in all t3. Hence the need to check if a field exits or not.
I had an idea to solve that problem by using * to load all fields.
That lead to problem no2: More than one field has the same name => synthetic keys.
I tried to solve that problem by using Qualify, so that date would be called t3.Date.
the problem with this solution is that Qualify adds a table number each time it reads a table