Question : Difference between a user defined stored procedures and function?

I think I know what a "user defined" store procedure is.  What's a function?

Is that the C# code that calls the stored procedure?

Answer : Difference between a user defined stored procedures and function?

natural join
right join
left join
full join

if a table is joined with itself this is self join

--> http://www.w3schools.com/sql/sql_join.asp