Solving the nestjs typeorm not selecting join fields Problem with PostgreSQL

Discover how to efficiently retrieve join fields in NestJS and TypeORM with PostgreSQL. Learn the step-by-step solution to your query issues.
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This video is based on the question https://stackoverflow.com/q/76942843/ asked by the user 'Sunil Garg' ( https://stackoverflow.com/u/2172547/ ) and on the answer https://stackoverflow.com/a/76943130/ provided by the user 'Hai Alison' ( https://stackoverflow.com/u/12599279/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Issue with NestJS TypeORM and PostgreSQL

When working with relational databases, especially in a Node.js environment like NestJS, it's common to face challenges while trying to retrieve related data using TypeORM. One frequent issue developers encounter is when joining tables, the expected fields do not get selected, resulting in incomplete data returns.

Let's consider a specific scenario:

The Problem

You have an entity defined in your NestJS application, as shown below:

[[See Video to Reveal this Text or Code Snippet]]

With the following query:

[[See Video to Reveal this Text or Code Snippet]]

Despite expecting to get results that include the entityId and userId, the output only returns:

[[See Video to Reveal this Text or Code Snippet]]

The userId and entityId fields are missing, leaving you puzzled.



The Solution: Loading Relation IDs in TypeORM Queries

Fortunately, the solution to this issue is straightforward. When using TypeORM, you need to explicitly tell it to load the relation IDs. This can be accomplished by adding an option to your query.

Step-by-Step Fix

Include loadRelationIds Option

Modify your query to include the loadRelationIds: true option, which is essential for fetching the IDs of the relationships defined in your entity.

Here’s the revised query:

[[See Video to Reveal this Text or Code Snippet]]

Executing the Query

Now, execute this modified query, and you should see the output includes all necessary fields, not just the id field.

Retrieving the Data

By using the above query, your data return will now contain the relationships along with their IDs, allowing you to access information across related entities directly.

Example Output After Modification

The expected output after applying the change will look something like:

[[See Video to Reveal this Text or Code Snippet]]



Conclusion

In summary, when using TypeORM with NestJS to create complex queries involving relations, ensure that you include the loadRelationIds option in your query. This small but crucial step will enable you to retrieve all the relevant fields you need from your joined entities.

Implementing this technique will significantly enhance your data handling capabilities in NestJS applications using PostgreSQL. If you continue to encounter issues, double-check your entity definitions and query parameters for completeness.

Feel free to reach out for further assistance or clarification on any related topics!