You can specify which columns in your tables are to be compared by clicking on the Columns tab. This shows you the columns in your tables / queries.
on the left grid, select the Compare checkboxes to include or exclude a column from the compare.
on the right grid, you can move entries up or down. You do this to indicate which column in second table matches the column in the first table.
the Insert Entry and Delete Entry buttons are useful if you need to add a blank row to the grid. You will need to do this if your first table has a column which doesn't correspond to any column in the second table. In this case you match this column to a blank entry.
columns which will not be compared are "greyed-out".
the Key checkbox can be used to specify which columns in the table comprise the unique key
