Luckily my system administrator makes automatic backups of the databases, so he just dropped all of the tables and then restored my database from about a day before. After a lot of research, I found it was basically impossible to restore the affected tables without a backup because not only did it change a lot of stuff I didn’t understand with some of the columns and the index of the posts table, but it changed every single “post_status” entry to “0” instead of what they should be– “publish,” “draft,” and etcetera. Anyway, things were really messed up.
My advice to anyone who has a similar problem and comes across this post is:
A.) Look before you leap! Go over your settings many times before installing!
B.) Backup the databases regularly and especially when installing or upgrading!
Thank you, crishajer, for your help. I greatly appreciate the time you took. Again, thank heaven for sysadmins with more sense than site administrators!