Question: what is the difference between count(*) and count(1) in oracle?
Answer: The difference is simple: COUNT(*) counts the number of rows produced by the query, whereas COUNT(1) counts the number of 1 values. ... If you use COUNT(column), the database must actually inspect the individual values in the column, since it will not count NULLs. Aggregate functions like COUNT and SUM always ignore NULLs.