Previous post show how to create floating content and fixed floating content using for bookmarking tool and feedback button. But this post show how to create a main menu fixed on top when the pages is scrolling. Simple jquery tricks do it easily. For this you need to learn clearly css,html and jquery. But not very hard to try.
A Candidate Key can be any column or a combination of columns that can qualify as unique key in database. There can be multiple Candidate Keys in one table.
In other words Candidate keys are all columns in a table that are not dependent on other columns in the table. All candidate keys are not primary keys. We choose one of the candidate keys as primary key. A table may contain more than one candidate key but only one primary key column per table is allowed.