Recall & Review
beginner
What is aggregation in SQL?
Aggregation in SQL means combining multiple rows of data to produce a summary result, like totals or averages.
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beginner
Why do we need aggregation in databases?
We need aggregation to get useful summaries from large data sets, such as total sales, average scores, or counts of items.
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beginner
Name a common SQL function used for aggregation.
Common aggregation functions include COUNT(), SUM(), AVG(), MIN(), and MAX().
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intermediate
How does aggregation help in real-life business decisions?
Aggregation helps businesses see overall trends, like total revenue or average customer rating, which guide better decisions.
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beginner
What would happen if we didn’t use aggregation on large data?
Without aggregation, it would be hard to understand big data because we’d only see many individual rows, not summaries.
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What does the SQL function COUNT() do?
✗ Incorrect
COUNT() returns the number of rows that match the query.
Why is aggregation useful in SQL?
✗ Incorrect
Aggregation combines multiple rows to produce summary results like totals or averages.
Which SQL function calculates the average value of a column?
✗ Incorrect
AVG() calculates the average (mean) of numeric values in a column.
If you want to find the highest price in a product list, which function do you use?
✗ Incorrect
MAX() returns the highest value in a column.
What is a real-life example of using aggregation?
✗ Incorrect
Counting total sales is an example of aggregation to get a summary.
Explain why aggregation is important when working with large data sets.
Think about how many rows can be overwhelming without summaries.
You got /4 concepts.
Describe some common SQL aggregation functions and what they do.
Focus on counting, adding, averaging, and finding minimum or maximum.
You got /6 concepts.