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In a relational database, there are two types of keys, primary key and unique key. Both the keys specify the values present either in one column or in more columns. The primary key is mainly responsible for indicating each record present in the table. The unique key prevents duplicate values. In a database, both keys can have more than one column. For retrieving and storing data in a database or table, these keys play a vital role. In a table, there is a series of columns that contains information and this information can be retrieved with the help of instructions. Now, for giving instructions these keys are required. Both the keys have different significance and play a different role in a database and retrieve different information. So, it becomes important to understand both of them in detail.
Primary Key
A primary key is a table column that specifically identifies rows in a table. This specific key maintains the integrity constraints of the table. There can only be one primary key in a table. When a candidate has chosen a primary key, the other keys become alternate keys. The primary key will not accept duplicate and NULL values. The primary key’s value in a table is chosen precisely as it infrequently changes. Each key will have a unique discrepancy. While filtering, alternate keys will be used as primary keys. A primary key will comprise real-world observables, and then it is also called a natural key. When the trait is used to identify outside the database, it is a surrogate key.Unique Key
Keys give the basis for database use in any table. A unique key is a seeker in relational database operational systems. All the seeker keys of relation will specifically identify the records of the connection, but only one can be used as the primary key of the association. The existing candidate keys are known as unique keys because they can specifically help you to identify a record in relation. Unique keys are also known as alternate keys. Unique keys are another option instead of the primary key of the association. They have a specific constraint.Comparison between Primary Key and Unique Key
There are quite a few differences between these two keys based on their functions. The critical differences between Primary and Unique keys are:- There can only be a single primary key in a table, whereas many unique keys can be present
- The primary key aim is to exert entity integrity; whereas on the other hand, the goal of a unique key is to implement individual information
- In the primary key, the general Index is crowded whereas, in the unique key, the general index is not crowded
- There are no empty or invalid columns in the primary key, whereas a unique key allows many empty columns
- There are no duplicate keys in the primary keys while in a unique key if one or more essential parts are null or invalid duplicate keys can be used
