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Rules to observe when designating a Primary Key In some cases, using a surrogate key (an artificial, system-generated identifier) may be the best option, as it ensures uniqueness, stability, and simplicity while separating the primary key from any meaningful data. Duplicates or null values: A bad primary key would allow duplicate or null values, making it difficult to uniquely identify records and maintain data integrity.When designing a database schema, carefully consider the choice of primary keys for each table, keeping in mind the characteristics of a good primary key and the pitfalls to avoid.Composite keys with too many columns: While composite keys can help ensure uniqueness, using too many columns can complicate queries and negatively impact performance.

Sequentially generated values with predictable patterns: While auto-incrementing integers can be convenient primary keys, they may not be suitable for all scenarios, especially when security or privacy is a concern, or when distributed databases are involved.Large or complex data types: Using large or complex data types (e.g., long strings, large numbers, or binary objects) as primary keys can negatively impact database performance due to increased storage requirements and slower indexing.This data might change over time or may not be unique, which can lead to integrity issues. Meaningful data: Using a column with meaningful data (e.g., Social Security numbers or email addresses) as the primary key can be problematic.Large or complex primary key values can slow down database performance.

Minimal size: Smaller primary key values, such as integers or short strings, are generally more efficient for indexing and querying.

Single-column primary keys are often preferred, but sometimes a combination of columns (composite key) is necessary to ensure uniqueness.

Simplicity: Ideally, a primary key should be as simple as possible.

Changing primary key values can lead to data integrity issues and require updates to foreign key references in related tables.

Stability: A good primary key should have stable values that do not change over time.

Non-null: Primary key values should not be null or empty, as this would hinder their ability to uniquely identify records.

Uniqueness: Each value in the primary key column should be unique to ensure that each record can be uniquely identified.

Here are some characteristics of a good primary key and some pitfalls to avoid when choosing a primary key: The choice of a primary key can have a significant impact on database performance and ease of use. It helps to ensure data consistency and integrity. What is Database Primary Key?Ī primary key in a database is a unique identifier for each record in a table.

Third Normal Form Lesson 11 Primary keys Objective Define database primary keys.

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