The Tab Path column maps where in the hierarchy the tabs go.  It is also used in constructing Urls for the tab.

If you have a tab called 'thing', it will have a tab path of //thing.  If 'thing' is set to have a parent tab of 'this', then the tab path will be //this//thing.  The tab path also takes out any spaces or illegal punctuation from the tab name, so 'my tab' becomes //mytab.

If you are created the tabs manually through a sql statement you'll have to make sure you set the parent tabid correctly, plus parse the tab path correctly.

I would recommend writing a throw-away tab import program that references the DOtNetNuke.dll and uses the TabInfo object and TabController to create the tabs, rather than trying to nail it all down in Sql.  You'll get fewer errors and it will take less time in the long run.