Normally, errors occurs for data-change statements (such as
INSERT or
UPDATE) that would violate
primary-key, unique-key, or foreign-key constraints. If you
are using a transactional storage engine such as
InnoDB, MySQL automatically rolls back the
statement. If you are using a nontransactional storage engine,
MySQL stops processing the statement at the row for which the
error occurred and leaves any remaining rows unprocessed.
MySQL supports an IGNORE keyword for
INSERT,
UPDATE, and so forth. If you
use it, MySQL ignores primary-key or unique-key violations and
continues processing with the next row. See the section for
the statement that you are using (Section 12.2.5, “INSERT Syntax”,
Section 12.2.11, “UPDATE Syntax”, and so forth).
You can get information about the number of rows actually
inserted or updated with the
mysql_info() C API function.
You can also use the SHOW
WARNINGS statement. See
Section 22.9.3.35, “mysql_info()”, and
Section 12.4.5.41, “SHOW WARNINGS Syntax”.
Currently, only InnoDB tables support
foreign keys. See
Section 13.6.5.4, “FOREIGN KEY Constraints”.