In the last few days I discovered it's good at medium-complexity SQL, not at really more complex ones. I'm struggling like 4th day with Claude, ChatGPT, Gemini

In the last few days I discovered it's good at medium-complexity SQL, not at really more complex ones. I'm struggling like 4th day with Claude, ChatGPT, Gemini and Deepseek. All could do some good analysis with some low-hanging fruit improvements, but all went completely crazy when trying to optimize more complex things, getting into loops proposing the same changes over and over, outputting invalid SQL, and gemini even forgot what we were doing, asking me if I could paste again the query i included in the very first message. Maybe the chain of thought models would handle this better, but I believe I hit the limit for the standard ones.