What is the Full Form of PK? 

The full form of PK is Primary Key. It is also known as Primary Keyword and is a unique identifier column in a Relational Database which is different for each record. The primary key can be the driver’s license number, telephone number with area code or vehicle identification number (VIN). A relational database has only one primary key and every row must have a primary key value which means no row should have a null value. 

The selection of the primary key may depend upon the choice of the relational database administrator. According to the changing needs,  it can happen that the choice of primary key changes. This means that for example, in one case identifying people uniquely may be more feasible on the basis of their driver’s license number but in another case, it can happen that choosing their telephone number as the primary key is a better option.

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Importance of Primary Keys

A primary key serves an important role in a relational database management system (RDMS) like Oracle database or SQL server. Every row in a database should have a unique primary key and it should be either based on a single attribute or a group of attributes. Mentioned below are some of the advantages of a primary key: 

• Aids in the accessibility of rows. 
• Sets up the relationship between tables. 
• Primary keys make sure that fields are not null 
• Helps in altering specific records which includes updating or deleting them. 
• Ensures that there is no duplication of data in the tables. 
• Identifies every record uniquely. 

Also Read: What is Database Architecture? 

How to Choose a Strong Primary Key? 

A strong primary key sets up a foundation for an efficient database design. A database developer should keep the following things in mind which will help in creating a strong primary key: 

• Relevance – The data value used to create primary keys should stay relevant which means that it should mean the same thing after 5 years. 
• Length – The primary key should be concise and consist of one column whenever it is possible. 
• Data Type – The data type of the primary key should be numeric which means integer or a concise fixed-width character. 
• Non-null data value – The data value of the primary key should not be null and remain fixed over time. 
• Uniqueness – A primary key should always be unique which means that no two records should have the same primary key. 
• Simplicity – While creating the primary key whole numbers or short character strings should be taken into account and things like special characters, spaces or differential characterisation should be avoided. 
• Stability – Values making up the primary key and columns in the primary key should not change. For example, if the column is removed from the primary key then the combination will cease to be unique.

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