What is the difference between unique key and primary key?

I am a novice C-Sharp(C#) programmer. I am working for a student project.

By default MS SQL can be used easily with this language.

But I have a database on MySQL.

Could I use MySQL server to query with C-Sharp(C#) language?

How can I connect MySQL database?

Please help by sharing your knowledge.

I am working on an Oracle database and I need information about SQL and PL/SQL. I heard many Oracle apps are based on PL/SQL. What are the difference between the two and do I need to use PL/SQL or Java to encode triggers and procedures?

I am using SQL Server 2008. I have provided an image of the output that I intended to make. I want to combine multiple rows and make a single ID, while bringing the Non-Null columns into whole or consolidate them. Please look at the rows and columns below:

I need help with MySQL query. I want to create a function that will do a lot of sorting on my database. Considering the code below, can I change the default value of a WHERE argument, that will sum up to anything? So the default value of the said argument will find everything on the database.

MySQL Database is under my remote server and a JPS application running under a different server. I need help in writing a trigger for a particular table to be used for audit trail. I can open MySQL server using MySQL Front Utility and can upload JSP codes through FTP to that server.

My question is, how I can write triggers using remote server for MySQL Database?

I need help on installing WordPress as I am encountering problems with the connections. I have a new site on a specific IP with the same machine and MySQL is under another IP. According to the articles and forums that I’ve read, I may need to open MySQL and accept outside connections. But I don’t know how to do that.

Can someone send me ways on how to accept MySQL connections and use it on my default IP.

I want to make a column that can add the records together on my MySQL database. The record will add up the score of my entire league, taking the points from a race and add it with another race. The purpose of this is to compute the overall points of my entire league for one season. How can I possibly perform it?

My website is very slow and my hosting company made a report of my present loading average. The value is 2.39. Is that high or just normal? What is the capacity of MySQL server? And what average do I need to attain to make my site run faster? 

How can I download and install MySQL to my PC? It has command line interface and other options that can be useful. I want to know if I can use it to install MySQL to PC. And also, I need detailed instructions on how to properly do it.