Common SQL Theory Questions

Common SQL theory questions focus on fundamental concepts that form the base of database understanding. These questions are frequently asked in interviews to test clarity on how relational databases work and how SQL is applied in real-world scenarios. Typical topics include database structure (tables, rows, columns), types of keys (primary, foreign, unique), normalization, indexing, and constraints. Candidates are also expected to understand differences between commands like DDL, DML, DCL, and TCL. Other important areas involve concepts such as joins, subqueries, views, transactions (ACID properties), and differences between DELETE, TRUNCATE, and DROP. These questions help assess conceptual depth rather than just query-writing ability. Overall, this set of theory questions is essential for building a strong SQL foundation and performing well in technical interviews related to data analysis, backend development, and big data roles.