You need the moving average of the last 3 rows including the current row. Which frame clause achieves this? SQL Data AnalystHard Try Now
Which isolation level prevents dirty reads but still allows non-repeatable reads? 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
What is the purpose of QUALIFY in SQL (supported in BigQuery, Snowflake)? 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
You need to find the second-highest salary in a table without using TOP/LIMIT. Which approach works in standard SQL? 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
What does the EXISTS operator do differently from IN when used in a subquery? 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 does EXPLAIN (or EXPLAIN ANALYZE in PostgreSQL) show about a query? SQL Data AnalystHard Try Now
What does ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING as a window frame produce? SQL Data AnalystHard Try Now
