mySQL INSERT IGNORE不会“忽略". [英] mySQL INSERT IGNORE doesn't "ignore"

问题描述

据我了解，INSERT IGNORE会插入一个新条目(如果尚不存在)，如果存在，请忽略它.因此，我尝试这样做已有一段时间了，而且似乎没有用.这是我的尝试:

From my understanding INSERT IGNORE inserts a new entry if it doesn't already exists, if it does, ignore it. So I've been trying to do that for a while and it doesn't seem to be working. Here's my attempt:

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)

推荐答案

如 INSERT语法:

没有IGNORE的情况下，与表中现有的UNIQUE索引或PRIMARY KEY值重复的行会导致重复键错误，并且该语句将中止.使用IGNORE，仍不会插入该行，但不会发出错误.

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UNIQUE索引:

ALTER TABLE rss_feeds ADD UNIQUE INDEX (md5sum);

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