The weekly engagement report counts reviews with the expression SELECT count(comment_text) FROM catalog.reviews. The reported number comes out lower than the table's actual row count, and QA confirms that many customers submit a star rating only, leaving comment_text NULL. The report must count every review. Which expression and explanation are correct?
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Correct answer: count(expr) counts only rows where expr is not NULL; count(*) counts every row, so the report needs count(*) to total all reviews
Reference: https://docs.databricks.com/aws/en/sql/language-manual/sql-ref-functions
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02 — The Myelin Layer · Canonical Discussion
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Official Answer (C): count(expr) counts only rows where expr is not NULL; count(*) counts every row, so the report needs count(*) to total all reviews
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