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Stupid NULLs More | Login | Reply

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count() (Score:1)

by Abigail (26)

count(expression) counts the number of times expression is not NULL. Which explains your answer. I always use 'count(*)' if I want to count the number of rows - several databases have optimized 'count(*)'. Others use 'count(1)' to count rows.
- Re: (Score:2)
  
  by Ovid (2709)
  
  Regrettably, this is something that much documentation [mysql.com] does not make clear. I'm expecting count() to return the number of instances of a particular value. Given that NULL can be thought of as "unknown", I suppose one could argue that it makes sense that it doesn't count the number of values. However, it also seems reasonable for one to assume that count(some_field) will return how many unknown values there are.
  Your explanation is perfectly correct. I'm just frustrated that an arguably "intuitive" answe
  - Re:count() (Score:1)
    
    by Aristotle (5147) <pagaltzis@gmx.de> on 2006.10.02 22:51 (#50687) Homepage Journal
    
    Ditto Abigail about intuition. I think the way COUNT works in SQL w.r.t. NULLs is actually useful and helpful.
    
    Your stance about NULLs reminds me about the saying about GOTO and the apprentice, the journeyman and the master. (Not that I can claim to be a master, mind…)
    
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