1. Number of Records:
The count(1) and count(*) returns same number of records, as its return the number rows in the table
including the NULL records.
While Count(Expression) return the number of null records for which expression evalutes.
2. Performance Factor.
There is no significance difference in performance onwards release R8 oracle.
I will say don't invest too much time on this topics.
Source doc Link
http://www.oracledba.co.uk/tips/count_speed.htm
https://asktom.oracle.com/pls/asktom/f?p=100:11:0::NO::P11_QUESTION_ID:1156159920245
The count(1) and count(*) returns same number of records, as its return the number rows in the table
including the NULL records.
While Count(Expression) return the number of null records for which expression evalutes.
2. Performance Factor.
There is no significance difference in performance onwards release R8 oracle.
I will say don't invest too much time on this topics.
Source doc Link
http://www.oracledba.co.uk/tips/count_speed.htm
https://asktom.oracle.com/pls/asktom/f?p=100:11:0::NO::P11_QUESTION_ID:1156159920245
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