No col or colgroup:

Data | Data | Data
Data | Data | Data
Data | Data | Data

col elements with align=center on second col:

Data | Data | Data
Data | Data | Data
Data | Data | Data

colgroup and col elements, with align on colgroup so 2nd and 3rd columns centered:

Data | Data | Data
Data | Data | Data
Data | Data | Data

colgroup and col elements, with align on col so 2nd column centered:

Data | Data | Data
Data | Data | Data
Data | Data | Data