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Handle NULL Ages
Many passengers have missing ages. Write a SQL query to show the average age by class, but replace NULL ages with the overall average age before calculating. Return pclass, avg_age_raw (with NULLs), and avg_age_filled (NULLs replaced). Order by pclass.
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Schema
passengers
| passenger_id | survived | pclass | name | sex | age | sibsp | parch | fare | embarked |
|---|---|---|---|---|---|---|---|---|---|
| 1 | 0 | 3 | Braund, Mr. Owen Harris | male | 22 | 1 | 0 | 7.25 | S |
| 2 | 1 | 1 | Cumings, Mrs. John Bradley | female | 38 | 1 | 0 | 71.28 | C |
| 3 | 1 | 3 | Heikkinen, Miss. Laina | female | 26 | 0 | 0 | 7.93 | S |
Expected output: avg_raw: 30, avg_filled: 30 (NULL to 30)
Hint
Concepts
SELECT NULL Handling COALESCE Aggregation GROUP BY Subquery
Practise the topic: SQL practice questions · NULL handling practice · GROUP BY exercises · CTE practice
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