What is the easiest way to design a SQL database schema?

2 Identify your relationships

The next step is to identify your relationships, which are the connections or associations between your entities. Relationships can be one-to-one, one-to-many, or many-to-many, depending on how many instances of each entity can be linked to each other. For example, a one-to-one relationship exists between a customer and a payment method, since each customer can have only one payment method and vice versa. A one-to-many relationship exists between an order and a product, since each order can contain multiple products, but each product can belong to only one order. A many-to-many relationship exists between a product and a category, since each product can belong to multiple categories, and each category can contain multiple products. You can use symbols or labels to indicate the type and direction of each relationship on your diagram or spreadsheet.

3 Choose your keys

The third step is to choose your keys, which are the columns or fields that uniquely identify each row or record in your tables. Keys are essential for ensuring data integrity and consistency, as well as for joining data from different tables. There are two types of keys: primary keys and foreign keys. A primary key is a column or a combination of columns that uniquely identifies each row in a table. For example, a customer ID or an order ID can be a primary key for the customer or order table. A foreign key is a column or a combination of columns that references the primary key of another table. For example, the customer ID column in the order table can be a foreign key that references the customer ID column in the customer table. You can use conventions or rules to name your keys and indicate them on your diagram or spreadsheet.

4 Normalize your tables

The final step is to normalize your tables, which is the process of organizing your data into smaller and simpler tables that avoid redundancy and inconsistency. Normalization follows a set of rules or principles that help you eliminate duplicate data, reduce data anomalies, and improve data quality and performance. There are different levels of normalization, but the most common ones are the first, second, and third normal forms (1NF, 2NF, and 3NF). To achieve 1NF, you need to make sure that each table has a primary key and that each column contains only one value. To achieve 2NF, you need to make sure that each table has only columns that depend on the whole primary key and not on a part of it. To achieve 3NF, you need to make sure that each table has only columns that depend on the primary key and not on other columns. You can use tools or checklists to verify that your tables meet the normalization criteria.

5 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?