What is the floor() function in SQL?

It is a functions that rounds up real values in form 4.34336… into 4 - that is int/integer value type of numerical data.

The SQL FLOOR() function rounded up any positive or negative decimal value down to the next least integer value. SQL DISTINCT along with the SQL FLOOR() function is used to retrieve only unique value after rounded down to the next least integer value depending on the column specified.