At what point is it typically appropriate to start practicing SQL problems on platforms like LeetCode?

I’m currently learning SQL and have a decent grasp of the theory of topics I’ve also completed SQLBolt. But I’m still not feeling confident in my SQL skills. I’ve tried working through problems on LeetCode, but I’m struggling to pass all the test cases for queries—even when the query itself seems correct. I can’t seem to wrap my head around how LeetCode works. How much theory should I know first, and do you have any tips for building confidence in writing queries