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What is the difference between COUNT(*), COUNT(col), and COUNT(DISTINCT col)?

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01

Understand the problem

Explain COUNT variations.

count
02

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03

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COUNT(*) counts all rows; COUNT(col) counts rows where col is not NULL; COUNT(DISTINCT col) counts distinct non-NULL values. Choosing the right one matters when NULLs or duplicates are present.

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SQLCOUNT Variants Playground
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