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Is it better to have a SQL table with a column that is almost always empty or a separate table with a foreign key?

I am trying to save what type of data is on a field, text, number or list. If the type is text or number that is it, but if it is a list I need to save what options it has on a string. I was thinking what would be the most efficient way of saving this, for storage and performance.

My ideas are creating a column "list" on the original table, this column would be empty for most entries but if the type is list then it would have that string. Or I could create a separate table with just 2 values,one primary key and foreign key to contain the id of the row in the original table and a mandatory string fiel to save the options.

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>Solution :

In terms of storage and performance, it is generally better to have a separate table with a foreign key when you have a column that is almost always empty. Here’s why:

  1. Storage Efficiency: Creating a separate table for the options would save space in the database because you only need to store the options for the specific rows that require them. If you have a large number of rows in your main table where the "list" column is empty, it would be inefficient to allocate space for that column in each row.
  2. Database Normalization: By creating a separate table with a foreign key, you can adhere to database normalization principles. This allows you to maintain data integrity and avoid redundant data. It also provides better flexibility for managing and querying your data.
  3. Performance Optimization: When querying the data, having a separate table with a foreign key allows you to easily join the tables and retrieve the necessary information. This approach can be more efficient than searching for empty values in a large table with many rows.

By using a separate table, you can optimize storage usage, maintain data integrity, and improve query performance. However, it’s important to consider the specific requirements and context of your application before making a final decision.

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