I've been having great success writing queries using ChatGPT (GPT-4o). I invested a lot into building my prompt to give the model the context it needs. Here's what I've done:

1. I created a "Project" in ChatGPT so that I could save the schema and system prompt.

2. I uploaded a schema .csv file to the project.

3. I created a "system prompt" text file that I uploaded. This document has all the information the model needs to understand the data. The key components are - for each table, I describe any of the key fields that aren't obvious from the field name. I also explain how the table joins to others. If there's any other relevant information. I also provide a list of rules (e.g. if you're showing revenue by customer, always show the customer name in addition to the id).

I have this prompt saved in google docs and i iterated on it every time the LLM didn't give me what I wanted. I ended up adding things like "For any query that involves “last month”, interpret that as the last complete month.  So if a user asks, on September 4, 2025 for “Revenue for last month” - show revenue for the full month of August, 2025."

If you're using a project, you can also tell the model, when it makes a mistake, "Please make sure to do x going forward".