As we all know DBMS is very important for interview point of view. So, here is my some important topics on dbms which are generally asked in interviews.
Basic

Explain DBMS
Different languages in DBMS (DDL, DML, DCL, TCL with Example)
ACID properties in DBMS with real life example (Very Important)
Data abstraction in a DBMS
Types of Join
Difference between JOIN and UNION
Intermediate

What is a lock in DBMS and types
Keys in DBMS
Ready with keywords like - DELETE, DROP, DISTINCT, GROUP BY, ORDER BY, VIEW
Find nth largest salary in Employee data
LIMIT and sub-query
Advance

Normalization and Denormalization
Different tier architecture in a DBMS
Ready with FOREIGN KEY and Multiple JOIN related queries
Some Apps like Instagram, data fetching query and database design part