To resize columns and bands, drag the right edge of the target column/band header:
To change a column’s width so that it displays its contents compactly in their entirety, do one of the following:
Double-click the right edge of the column header.
Right-click the column’s header and select Best Fit:
To change the widths of all columns so that they display their contents in the best possible way, right-click the header of any column and select Best Fit (all columns).