The candidates who struggle rarely forgot a keyword. They think row by row.
SQL describes the shape of an answer and lets the engine find it. Think in Sets teaches that shift for the SQL interview, from the interviewer's side of the table: from the first SELECT to window functions and query plans.
Each chapter opens with the idea in plain language and a diagram. Then, one question per page, it shows what the interviewer is testing, the answer they want to hear, how to say it out loud, a real query with the result it produced, the green and red flags that decide it, and a short "Your turn" task that turns recognition into fluency.
Inside:
- The shape of data, and the logical order in which SQL resolves a query
- Asking the first question: filtering, sorting and the clauses every interview expects
- Joins and the rows each type keeps; grouping and aggregating
- Subqueries and CTEs, window functions, and three-valued logic with NULL
- Reading a query plan
- The rounds, and a one-page cheat sheet
More than 100 interview questions run on four small tables: a sales fact table with its customer, item and employee dimensions, built with the messiness interviews probe (a customer who never ordered, an item never sold, missing discounts, an employee with no region). Every query was run in the LucidPlexus Workbench on DuckDB, in standard SQL that carries with small changes to PostgreSQL, Snowflake, BigQuery and SQL Server.
Every purchase includes the four tables as CSV files, ready to load.
The Data Interview Series · Interview Edition. LucidPlexus.