从SQL Server 2014 Express降级到SQL Server 2012 Express

Question

I had SQL Server 2012 Express installed on my PC at work, but we received a file from a client the was created in SQL Server 2014. Please keep in mind, I am newbie, and I only made this mistake about 7 months ago

I tried to install SQL Server 2014 Express as another instance on my PC along with SQL Server 2012. After noticing that my new SQL Server instance did not work and my old SQL Server did not work, I looked online and found that what I did was a step up from what an ape would do. Always read before attempting an install.

After un-installing SQL Server 2014 I tried to relaunch SQL Server 2012, but it would not connect to my instance that I was able to just before.

I now get this error:

Cannot connect to STID02\\SQLEXPRESS.

A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified) (.Net SqlClient Data Provider)

I have also read this thread Can't connect to SQL Server 2014 Express and found that the SQL Server service is stopped and I cannot start it, and the SQL Server Agent Service is stopped and won't start either.

I have not been effected by this until recently, I need to do some testing with DB's but I need my local instance to do the testing. I would appreciate any advice, as I am still new to SQL Server and most computer related things I would be very thankful to those how can dumb it down extremely low.

Thank you -Anthony

Answer 1

In short, uninstall everything, then reinstall the version you want to use.

Some configuration files must have been overwritten by SQL Server 2014. Don't worry, it can be fixed.

First: do you need any of your existing databases? I assume not as you haven't been using SQL Server for the last 7 months. If you do need some of the databases you'll find the .mdf , .ldf files in you SQL Server installation folder somewhere in the DATA folder.

Then: Uninstall SQL Server 2012 - note that since you've corrupted your current installation it might happen that some registry entries will be bad and/or services or libraries won't be removed. In that case fix the registry entries using some tool, like CCleaner , and try again to remove those programs/services.

Last step: reinstall whichever version you want. If you needed your previous databases overwriting the new mdf/ldf files should do the trick (of course while the server is not running). You can check the server's state from the SQL Server Configuration Manager or from Services.