[TYPO3-english] question about 'upgrade'

[tom liu]

Hi ,

I upgraded my typo3 4.2 to 4.5 according to this documentation:
http://docs.typo3.org/typo3cms/InstallationGuide/Upgrade/Index.html

But when I am on step 4, Compare and Update the Database, I got some
questions:
Questions:(this happens on this page: Database Analyser->COMPARE)
1. By default the below group(Italic and bold) is checked, but after I
click 'Write to database', it still shows up under "Table and field
definitions should be updated", why?
*select/deselect all
 ALTER TABLE fe_users CHANGE functions functions TEXT;
Current value: text
 ALTER TABLE fe_users CHANGE industries industries TEXT;
Current value: text
...*
2. I got a little bit confused about the query:
example:
ALTER TABLE fe_users CHANGE functions functions TEXT;
Current value: text
it is already 'text', why need to change?

3. If I do not do anything on 'COMPARE DATABASE' page, what will happen?

Tom