I'm having trouble with wordpress' database now

All of a sudden, all wordpress pages just went blank.

I decided it may be a good idea to upgrade to the latest version of wordpress. With a new database it works fine, but when i restored the old one, all the new wordpress pages went blank.

So, I tried copying just the data which included all the posts etc onto a new wordpress database, and wordpress worked but just gave an error because it couldn't access the posts, which is what i expected.

Therefore, I have narrowed it down to a problem with the database which is not related to posts, users or comments.

Does anyone know where I could start looking for what the problem might be? All wordpress pages are blank with the existing database, even the upgrade page. The install page, which generates a new databse functions fine however.

Many Thanks
Steve
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I've not really used Wordpress enough to know what the structure of changes between versions could be that might cause this problem.

How different was the version you were using originally, and the version you have just upgraded to? If it was a complete version update, and not just an incremental bug fix release, then the database structure may have changed and therefore existing tables from the original version would break. Normally if versions are quite different there is an upgrade path that needs to be followed. With Joomla for example their is a migration script you need to run on the database of a 1.0.x site before you can migrate to 1.5.x.

You should definitely get everything working properly with the original version first, before you then migrate/upgrade the site to a newer version.

Out of interest, why did you install a completely new version and then try to import the old database? Normally when upgrading a site you would just download the update, overwrite the existing files on the server and then run an upgrade script which would be included with the update. Unless wordpress isn't that advanced yet?
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You misunderstood, the upgrade didn't cause the problem. All the pages in the original version just failed to work.

Running the upgrade script won't do anything because the exisiting database has to be in place and that for some reason causes none of the wordpress pages (new or old), including the upgrade page to work.

The problem is not caused by upgrading. I just recieved an email the other morning saying that the site didn't work. I had not done any maintenance on it before then.

Since it didn't work, I thought I there may be a problem with some of the wordpress files, so thought it might be best to upgrade since we are using a 3 year old version, but as mentioned above, the database causes the new files to not work as well, which suggests that there is no problem with the wordpress files.
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As I said above, if a site isn't working as it is, running an upgrade is not going to fix it. You need to work out what is wrong with the existing site and fix it first or you will never get it working and just create more problems upgrading an already broken site.

Have you looked at the backup of the database. Are the posts actually still present in the database tables? If not then they are gone and you won't be able to ever get them back unless you have an older database backup with them still intact.
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That is true, but I thought at first that something had gone wron gwith one of the Wordpress 1.x files on the server, or maybe there could have been something wrong with the theme or something. If this were the problem, then the database would have no effect on the site. But the problem is in the database, and since I didn't have a new copy of 1.x to verify this with, i used the 2.x instead.

I have had a good look through the database. All the posts and comments etc are there. None of the important data is missing, but there is obviously something there which causes all wordpress pages to not do anything (regardless of the version).

I was just wondering if you or anyone else may have any idea of why a database would cause pages to go blank. I cannot find anything which is obvious, but I will have another good look.

It isn't a major problem as we will probably be getting rid of Wordpress in the near future anyway as part of remaking most of the site but it is just annoyiong when it doesn't work.
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Only thing I can think of is that the database character encoding has changed.
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