CTE Solution| Efficient Code
\nWITH cte AS (SELECT class, COUNT(class) AS num FROM Courses GROUP BY class)\nSELECT class \nFROM cte\nWHERE num>=5; \n
```\nWITH cte AS (SELECT class, COUNT(class) AS num FROM Courses GROUP BY class)\nSELECT class \nFROM cte\nWHERE num>=5; \n```
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