MySQL 8.0 Release Notes
MySQL 8.0 Source Code Documentation
NULL value means “no data.”
NULL can be written in any lettercase.
Be aware that the
NULL value is different
from values such as
0 for numeric types or
the empty string for string types. For more information, see
Section B.3.4.3, “Problems with NULL Values”.
For text file import or export operations performed with
LOAD DATA or
SELECT ... INTO
NULL is represented by the
\N sequence. See Section 13.2.9, “LOAD DATA Statement”.
For sorting with
NULL values sort before other values for
ascending sorts, after other values for descending sorts.