In first steps young DBA can greedily soak up all kinds of database knowledges: as RDBMS as NoSQL. We’re realising things like how table index works, how to optimize memory caching, write triggers and procedurs etc.. But we still can forget a simple command to create user or show tables list. Also we can get stuck when switching from MySQL to PostgreSQL or whatever else, cause command syntax is different.
At the day when this post was published, I didn’t have many ideas about “how database works”. As for RDBMS, as for NoSQL solutions. But someday I accidentally got one SQL task.