Keys are one of the most vital features in a relational database. Among the many types of keys, the primary key is widely used and appreciated. Let’s find out what kinds of primary keys are available, what a primary key does, and how to use it in a table. In this article, you’ll learn all about primary keys in relational databases. The topics we’ll cover include: An overview of relational database keys.
A natural key is used to provide simple, easy-to-remember values (or set of values) that are meaningful to the business as an identifier for each row, rather than using business-agnostic, system-generated values as primary keys for database tables. Before getting into detail about what a natural key is, you might want to read the article “On Keys” to fully understand the concept of keys in a database model and their different types.
Sometimes the naming convention you use requires a specific pattern for the primary keys’ names. That’s why you may want to set your own names for each primary key in your database model instead of using default ones. Go on reading to get to know how to do this in Vertabelo. To give your own name to a primary key, select the table that contains the primary key you want to name:
Primary keys may contain more than one column. Multicolumn primary keys are frequently used for junction tables, which are used to model many-to-many relationships. Select a table: In the Table properties panel on the right, check all the columns that you want inside the key: Now, you have a multicolumn primary key created: You can check out your SQL code by clicking the SQL preview button in the top right corner:
Sometimes there are columns in a table that don’t belong to primary key, but are still unique. To mark them as a unique, you have to create an alternate (unique) key containing it. Single-column alternate (unique) key Select the table with the column you want to make a unique. Then, click the Alternate (unique) key tab in the Table properties panel on the right: Click Add key:
Over the years, working as a data modeler and database architect, I have noticed that there are a couple rules that should be followed during data modeling and development. Here I describe some tips in the hope that they might help you. I have listed the tips in the order that they occur during the project lifecycle rather than listing them by importance or by how common they are.
Why do you need all of this normalization stuff? The main goal is to avoid redundancy in your data. Redundancy can lead to various anomalies when you modify your data. Every fact should be stored only once and you should know where to look for each fact. The normalization process brings order to your filing cabinet. You decide to conform to certain rules where each fact is stored. Nowadays the go-to normal forms are either the Boyce-Codd normal form (BCNF), which we will cover here today, or the third normal form (3NF), which will be covered later.
Today we continue our series of posts on data normalization. In the previous post on data normalization I explained what functional dependency is. Today we will talk about candidate keys in a table. A candidate key is a set of columns such that all other columns in the table are dependent on it, and the set is minimal, that is if you remove a column, then the resulting set is not a candidate key.