Differences and performance of Count (1) count (*) count (COL)

There is no difference between count (1) and count (*) (Execution Plan and statistics), and both are statistics.AllLine
Count (COL) Counts records whose Col columns are not empty. If an index exists, indexes can be used no matter whether or not Col is empty.
Test

HR @ orcl> select count (1) from t; Execution Plan ------------------------------------------------------------ plan hash value: 2966233522 bytes | ID | operation | Name | rows | cost (% CPU) | time | ------------------------------------------------------------------- | 0 | SELECT statement | 1 | 159 (2) | 00:00:02 | 1 | sort aggregate | 1 | 2 | table access full | T | 50356 | 159 (2) | 00:00:02 | explain HR @ orcl> select count (*) from t; Execution Plan ---------------------------------------------------------- plan hash value: 2966233522 bytes | ID | operation | Name | rows | cost (% CPU) | time | ------------------------------------------------------------------- | 0 | SELECT statement | 1 | 159 (2) | 00:00:02 | 1 | sort aggregate | 1 | 2 | table access full | T | 50356 | 159 (2) | 00:00:02 | -------------------------------------------------------------------