FrumRoll FrumRoll - 1 year ago 71
SQL Question

COUNT(*) Includes Null Values?

MSDN documentation states:

COUNT(*) returns the number of items in a group. This includes NULL
values and duplicates.

How can you have a null value in a group? Can anyone explain the point they're trying to make?

Answer Source

If you have this table


 Field1    Field2    Field3
   1         1         1
  NULL      NULL      NULL
   2         2        NULL
   1         1         1


 SELECT COUNT(*), COUNT(Field1), COUNT(Field2), COUNT(Field3)
 FROM Table1

Output Is:

 COUNT(*) = 4; -- count all rows even null/duplicates

 -- count only rows without null values on that field
 COUNT(Field1) = COUNT(Field2) = 3
 COUNT(Field3) = 2
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