Databases and Data Management
Core concepts
Understand relational concepts: tables, rows, columns, primary and foreign keys, and normalization to reduce redundancy. Know basic SQL: SELECT, INSERT, UPDATE, DELETE, WHERE, JOIN, GROUP BY, and aggregate functions. Distinguish DDL (schema) from DML (data). Understand transactions and ACID properties (atomicity, consistency, isolation, durability). Know indexing for performance, backups and restore, and the difference between a database and a data warehouse. Recognize data integrity constraints and basic access control.
Traps in questions
A common trap is confusing primary and foreign keys: a primary key uniquely identifies a row in its table; a foreign key references a key in another table to enforce relationships. Do not assume normalization always improves speed - it reduces redundancy but may require more joins. Questions may blur DELETE (removes rows, can be filtered) with DROP (removes the table structure). Also, ACID durability means committed data survives failure, not that data is encrypted.
Worked example / rule of thumb
A query listing orders with customer names is slow. Rule of thumb: joins on unindexed key columns cause slowdowns. Ensure the join columns (such as customer ID) are indexed and select only needed columns. This indexing-first reasoning answers most performance questions.
Exam focus
Expect key relationships, SQL statement purpose, ACID definitions, and backup/restore concepts.