SAP Query - illegal Join condition

Hello,

I am building a report in SAP QUERY by joining together 3 tables. For one field I have an illigal join condition. After analysis I think this is due to the fact that the CHAR lenght of the field in the first table is 18 and the CHAR lenght of the field in the second table is 35.

Questions:

1 Is it possible that this is the reason for my illegal join condition?

2 How can it be solved? Can I overwrite the lenght 'CHAR' in SAP QUERY?

thanx,

Stef