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Atul Varma
4,285 PointsNULL VALUES
At 2:34- Andrew says that COUNT function considers only NON NULL VALUES.(with the last_name example) But At 4:25: Andrew says that COUNT ignores ALL NULL Values and considers all values..
Confused!!!!!
2 Answers
Steven Parker
231,184 PointsCount with a specific column name ignores null values. But count with "*" as the argument considers all values.
Ryan Hartigan
3,425 PointsHow do we count distinct values while also including NULL as a distinct value? Steven Parker
Steven Parker
231,184 PointsThere are a few ways to do that, but my favorite is using COUNT(*) (which includes nulls) on a derived table of distinct values:
SELECT COUNT(*)
FROM (SELECT DISTINCT <your_column> FROM <your_table>)
For future issues, always create a fresh question instead of asking one as an "answer". It will reach more students that way.
Atul Varma
4,285 PointsAtul Varma
4,285 PointsThank you for your response.
Atul Varma
4,285 PointsAtul Varma
4,285 PointsHello Steven,
Could you recommend any book which I can follow to practice more or any link you can help me with ?
Thank you.
Steven Parker
231,184 PointsSteven Parker
231,184 PointsThere are some SQL exercises on W3 Resource and some tutorials that might be useful for reinforcement on SQL Zoo, including one on this particular topic Using Null.