The main difference between surrogate key and primary key is that surrogate key is a type of primary key that helps to identify each record uniquely, while the primary key is a set of minimal columns that helps to identify each record uniquely.
RDBMS is a DBMS designed using the relational data model. It helps to store and manage data in databases. Usually, there are multiple tables in a single database. Therefore, the keys help to connect the tables in a database. It helps to identify the relationships among data in various tables. Natural key and surrogate key are two types of primary keys.
Key Areas Covered
1. What is Natural Key
2. What is Surrogate Key
3. What is Primary Key
4. Difference Between Surrogate Key and Primary Key
–Comparison of key differences
Natural Key, Primary Key, Surrogate Key
What is Natural Key
A natural key is a key that can be defined naturally. In other words, it does not require adding an additional column or columns. For example, assume a user table that stores usernames and emails. As these columns help to identify the rows uniquely, these are primary keys. Furthermore, they were already available in the table. Therefore, they are natural keys.
What is Surrogate Key
Unlike a primary key, a surrogate key is a made-up primary key. In other words, it is a column added to the table. We can use a surrogate key when there are no columns to define as a natural primary key. These keys are unique as we create it when there is no other natural primary key.
Assume there is an employee table that stores employee records. It has the first name and last name. We cannot define the first name or last name as primary keys because multiple employees can have the same name. Therefore, the programmer can add an extra two columns as start time and end time. These times describe the shifts of each employee. These are newly added columns and help to identify each record uniquely. Therefore, those are surrogate keys. Generally, it is possible to use a surrogate key when there is no natural key or when the primary key is complex.
What is Primary Key
Primary key refers to the minimal set of columns that helps to identify a record in the table uniquely. The primary key has a few characteristics. Mainly, two rows cannot have the same primary key value. Moreover, each row should have a value for the primary key. Also, the primary key value cannot be null.
For example, assume a table called student. It has three columns: id, name and age. It is not possible to use the name or age as the primary key as multiple students can have the same name and same age. However, it is a good option to use the id as the primary key. It helps to identify each row using only that column. Therefore, id is the primary key of this table.
Difference Between Surrogate Key and Primary Key
A surrogate key is a non-natural key which aims to uniquely identify each row in the table. On the other hand, the primary key is a minimal set of attributes (columns) in a table that uniquely identifies tuples (rows) in that table.
Moreover, a surrogate key is a primary key, while the primary key is a candidate key.
Keys in RDBMS help to find the associations among data in various tables of a database. Surrogate key and primary key are two types of keys. The main difference between surrogate key and primary key is that surrogate key is a type of primary key that helps to identify each record uniquely, while the primary key is a set of minimal columns that helps to identify each record uniquely.
1.“DBMS Keys: Primary, Candidate, Super, Alternate and Foreign (Example).” Meet Guru99 – Free Training Tutorials & Video for IT Courses, Available here.
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