Search

Top 60 Oracle Blogs

Recent comments

Select COUNT(*) and COUNT(column) are different things!

Every now and then I see someone wondering why Oracle is “returning wrong results” for some count queries when counting using COUNT(column_name) instead of COUNT(*) or COUNT().

Oracle is actually returning correct results, its just that sometimes the people asking the questions haven’t realized that COUNT(column) is something semantically different from COUNT(*).

COUNT(*) operation counts all rows fed to it by execution plan branch under it.

COUNT(column) operation on the other hand counts all non-null values in that column from rows fed to it by execution plan branch under it.

And here’s a little example: