Primary key, Primary Index and Clustured Index,,,,
There are two main types of indexes that we can have on a Microsoft SQL Server backend Database. These are normal and clustered indexes. Normal index can be viewed as the index in the back of a book. We first look in the index for a topic. After finding the topic in alphabetical order we also find the page number or address of the topic in the book. We then use the address to easily find the topic. If we did not have this index we would have to search sequentially through the book and the larger the book the greater the effort and time to either find a topic or realize that it does not exist. This is similar to a normal index in the database where we have the data stored in one file and the index stored in another file in the order specified. The database engine using the index will first look in the index file then retrieve the address of the record that is used to locate the record in the data file. For clustered index the records in the data file are sorted in the order of the