What does FIRST_VALUE(revenue) OVER (PARTITION BY region ORDER BY sale_date) return for each row? SQL Data AnalystHard Try Now
In window functions, what is the difference between RANGE and ROWS frame modes? SQL Data AnalystHard Try Now
What is index cardinality and why does it matter for query optimization? SQL Data AnalystHard Try Now
Which execution plan operator typically indicates that an index is not being used and a full scan is occurring? SQL Data AnalystHard Try Now
What does ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING as a window frame produce? SQL Data AnalystHard Try Now
What does the EXISTS operator do differently from IN when used in a subquery? 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 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
