What value does the parameter to count function in MySQL pass in?

What value does the parameter to count function in MySQL pass in?

Querying total records in a user table

The information in the user table is as follows:

　　

1. SELECT COUNT (*) from USER

The result is: 3 records

2. SELECT COUNT (username) from USER

The result is: 3 records

3. SELECT COUNT (Sex) from USER

The result is: 3 records

4. SELECT COUNT (birthday) from USER

The result is: 0 records

5. SELECT COUNT (adress) from USER

The result is: 2 records

6. SELECT COUNT (1) from USER

The result is: 3 records

7. SELECT COUNT ( -1) from USER

The result is: 3 records

8. SELECT COUNT (0) from USER

The result is: 3 records

Thus, the following conclusions can be drawn:

COUNT (*) queries all records in the user table, regardless of whether they are null in the field;

Count (column name) queries all non-null records in the user table, excluding data that is null in the field;

Count (one number) queries all records in the user table, regardless of whether the field is null or not, and is counted;

What value does the parameter to count function in MySQL pass in?