Reading and Understanding Data Schemas Questions

Be able to look at a data schema (table structure) and understand what data is available and how tables relate. At the start of the assessment, you'll be given a schema. Spend a minute understanding it before writing queries. Understand primary keys, foreign keys, and data types.

EasyTechnical

26 practiced

You're given the following simplified e-commerce schema:

customers(customer_id PK integer, name varchar, email varchar, created_at timestamp)orders(order_id PK integer, customer_id integer FK -> customers(customer_id), total_amount decimal, placed_at timestamp)order_items(order_item_id PK integer, order_id integer FK -> orders(order_id), product_id integer, quantity integer, price decimal)

Spend a minute examining the schema. List the primary keys and foreign keys, describe relationships between tables and their cardinality (one-to-many, many-to-one), and name which columns you would inspect first for data quality issues and why.

HardSystem Design

33 practiced

Design a metadata catalog that stores table schemas, column descriptions, sample values, data owners, and lineage (upstream sources and downstream consumers). Describe the data model for the catalog, ingestion methods from various databases, UI features for analysts, and how the catalog helps schema understanding and impact analysis.

HardTechnical

28 practiced

For a near-real-time dashboard that requires sub-second response for simple counts and sums, discuss schema trade-offs between normalized OLTP-style tables and denormalized pre-aggregated tables. Cover freshness, write amplification, storage cost, and maintenance complexity in your recommendation.

EasyTechnical

24 practiced

In PostgreSQL, write a SQL query that returns all non-system tables in the public schema with their column names, data types, nullability, and comments if available. The result should include: table_name, column_name, data_type, is_nullable, column_default, and column_comment. Use information_schema and pg_catalog where necessary.

HardTechnical

32 practiced

Propose schema patterns to add auditing and change-tracking to tables for analytical traceability. Which columns would you add (created_by, created_at, updated_by, updated_at, change_reason), and what approaches would you use for row-level history (audit table, DB-level CDC, or append-only pattern)? Discuss queryability and performance trade-offs.

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