mysql_affected_rows() returns
the number of rows affected by the last INSERT, UPDATE or
DELETE query associated with
link_identifier. If the link identifier isn't
specified, the last link opened by
mysql_connect() is assumed.
注: If you are using transactions, you need to call mysql_affected_rows() after your INSERT, UPDATE, or DELETE query, not after the commit.
If the last query was a DELETE query with no WHERE
clause, all of the records will have been deleted from the
table but this function will return zero.
注: When using UPDATE, MySQL will not update columns where the new value is the same as the old value. This creates the possiblity that mysql_affected_rows() may not actually equal the number of rows matched, only the number of rows that were literally affected by the query.
mysql_affected_rows() does not
work with SELECT statements; only on statements which modify
records. To retrieve the number of rows returned by a SELECT,
use mysql_num_rows().
If the last query failed, this function will return
-1.
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See also: mysql_num_rows(),
mysql_info().