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Discover how to effectively `insert relational data` into MySQL tables using data from CSV files while applying conditions and default values.
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This video is based on the question https://stackoverflow.com/q/68290421/ asked by the user 'Muni' ( https://stackoverflow.com/u/16400907/ ) and on the answer https://stackoverflow.com/a/68292005/ provided by the user 'James K. Lowden' ( https://stackoverflow.com/u/451601/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Insert Relational Data Across Multiple MySQL Tables from CSV Files

In today's data-driven world, effectively managing and inserting data across multiple tables is crucial. Whether you're handling user data, user profiles, or login records, you'll often find yourself needing to insert new information from sources like CSV files. This guide will guide you through the process of inserting relational data into MySQL tables, ensuring that conditions and default values are met along the way.

Understanding the Problem

Let's say you have a CSV file that contains important information you want to insert into several MySQL tables. The CSV file consists of the following columns:

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You also have three MySQL tables set up as follows:

Tables Overview:

users: Contains user identifiers.

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logins: Records user logins.

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profiles: Contains user profile details.

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Given a CSV row, for instance, c,null,test2, you want to achieve two main objectives:

Insert entries into the logins table with a specific provider ID and user ID, ensuring the provider is set to "default."

For the profiles table, insert name if fallback_name is null, otherwise insert both name and user_id.

Step-by-Step Solution

1. Load the CSV Data into a Temporary Table

Before diving into the actual inserts, you should first load your CSV data into a temporary table, which we can refer to as T. This approach allows you to manipulate and extract the necessary information without altering your original data. You can discard this table later if needed.

2. Insert Into the Logins Table

To insert data from the temporary table T into the logins table, use the following SQL query:

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This query ensures that for each matching provider_id in the users table, an entry is created in the logins table with the provider set to "default."

3. Avoid Duplicate Entries

To safeguard against inserting duplicate entries, you can add a condition to prevent inserting records that already exist based on provider_id. Use this query instead:

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This modification ensures you only insert new logins that don't already exist in the logins table.

4. Insert Into the Profiles Table

Next, you need to handle the profile information. If fallback_name is null, you only need to insert the name. If fallback_name is present, insert both values. You can use the following query:

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Conclusion

By following these structured steps, you can successfully insert data from CSV files into multiple MySQL tables with the conditions and defaults you need. Handling data in this way helps maintain the integrity of your database while also streamlining the data entry process.

Now, you're equipped with the knowledge to effectively manage relational data using SQL and CSV files. Happy coding!