What are the guidelines for de normalization?
contain no redundant columns (matching join criteria columns) contain only those columns absolutely necessary for the application to meet its processing needs. be created periodically using SQL to join the normalized tables.
What happens when you store the data in a denormalized way in Rdbms?
Denormalization is the process of adding precomputed redundant data to an otherwise normalized relational database to improve read performance of the database. Normalizing a database involves removing redundancy so only a single copy exists of each piece of information.
When do we use denormalization in a database?
Denormalization is a strategy used on a previously-normalized database to increase performance. The idea behind it is to add redundant data where we think it will help us the most. We can use extra attributes in an existing table, add new tables, or even create instances of existing tables.
How to avoid a table join in denormalization?
We can avoid a table join by denormalizing the Messages table through adding the first_attachment_name column. Naturally, if a message contains more than one attachment, only the first attachment will be taken from the Messages table while other attachments will be stored in a separate Attachments table and, therefore, will require table joins.
Which is an example of a normalized database?
In a traditional normalized database, we store data in separate logical tables and attempt to minimize redundant data. We may strive to have only one copy of each piece of data in database. For example, in a normalized database, we might have a Courses table and a Teachers table.
When do you need to use denormalization for attachments?
Naturally, if a message contains more than one attachment, only the first attachment will be taken from the Messages table while other attachments will be stored in a separate Attachments table and, therefore, will require table joins. In most cases, however, this denormalization technique will be really helpful.