mySQL INSERT IGNORE 不是 "ignore"

Question

根据我的理解，INSERT IGNORE 插入一个新条目，如果它不存在，如果存在，则忽略它。所以我已经尝试这样做了一段时间，但似乎没有用。这是我的尝试:

insert insert ignore into rss_feeds (md5sum) values ("1234");
Query OK, 1 row affected (0.00 sec)

mysql> insert ignore into rss_feeds (md5sum) values ("1234");
Query OK, 1 row affected (0.00 sec)

mysql> insert ignore into rss_feeds (md5sum) values ("1234");
Query OK, 1 row affected (0.00 sec)

mysql> insert ignore into rss_feeds (md5sum) values ("1234");
Query OK, 1 row affected (0.00 sec)

mysql> select * from rss_feeds where md5sum="1234";
+------+--------+----------+---------+----------+--------+--------+---------+
| link | source | headline | updated | inserted | md5sum | itemid | emailed |
+------+--------+----------+---------+----------+--------+--------+---------+
| NULL | NULL   | NULL     | NULL    | NULL     | 1234   |   NULL |    NULL |
| NULL | NULL   | NULL     | NULL    | NULL     | 1234   |   NULL |    NULL |
| NULL | NULL   | NULL     | NULL    | NULL     | 1234   |   NULL |    NULL |
| NULL | NULL   | NULL     | NULL    | NULL     | 1234   |   NULL |    NULL | 
+------+--------+----------+---------+----------+--------+--------+---------+
4 rows in set (0.00 sec)

Answer 1

根据 INSERT Syntax 记录:

without IGNORE, a row that duplicates an existing UNIQUE index or PRIMARY KEY value in the table causes a duplicate-key error and the statement is aborted. With IGNORE, the row still is not inserted, but no error is issued.

您需要在md5sum 上定义一个UNIQUE 索引:

ALTER TABLE rss_feeds ADD UNIQUE INDEX (md5sum);