What is the purpose of QUALIFY in SQL (supported in BigQuery, Snowflake)? SQL Data AnalystHard Try Now
An analyst writes SELECT 100.0 / NULLIF(total, 0) to calculate a percentage. What problem does NULLIF solve here? SQL Data AnalystHard Try Now
Which slowly changing dimension (SCD) type overwrites the old attribute value without preserving history? SQL Data AnalystHard Try Now
What does PERCENT_RANK() return for the first row in a partition ordered by salary ASC? SQL Data AnalystHard Try Now
What does EXPLAIN (or EXPLAIN ANALYZE in PostgreSQL) show about a query? SQL Data AnalystHard Try Now
Which SQL feature allows you to pivot rows into columns dynamically without hardcoding column names? SQL Data AnalystHard Try Now
What is the result of a CROSS JOIN between a table of 5 rows and a table of 8 rows? SQL Data AnalystHard Try Now
An analyst writes: SELECT dept, AVG(salary) FROM employees GROUP BY dept HAVING AVG(salary) > 70000. What does HAVING filter on here? SQL Data AnalystHard Try Now
Which isolation level prevents dirty reads but still allows non-repeatable reads? SQL Data AnalystHard Try Now
