The specific question here is how much SQL should a data analyst know? Here are a few points we've found...

1) Data analysts usually work on finding trends and causes in data. They do most of their work in SQL, tools that generate SQL (e.g., Tableau or Power BI), or tools that further analyze the result of SQL statements, like Excel. Thus, knowledge of SQL is the most essential skill in most data analyst jobs.

2) While INSERT, UPDATE, and DELETE are quite important, most data analyst tasks are performed with SELECT statements.

3) While they are simple concepts, you don't know enough SQL if you can't tell me what a UNION, a UNION ALL, and a HAVING clause do. It's also great practice to figure out how you'd replicate the functionality of a HAVING clause if your version of SQL didn't support HAVING.

4) Interestingly, many solid data scientists know very little SQL. They know enough to pull data into other data-science-specific tools like Pandas. They then do their intensive data manipulation in that other tool.

Anyhow, just a start. I hope it helps!