按两列查找并删除重复行
我阅读了所有相关的重复问题/答案，我发现这是最相关的答案:
I read all the relevant duplicated questions/answers and I found this to be the most relevant answer:
INSERT IGNORE INTO temp(MAILING_ID,REPORT_ID)
SELECT DISTINCT MAILING_ID,REPORT_IDFROM table_1
;
问题是我想删除 col1 和 col2 的重复项，但还想将 table_1 的所有其他字段包含到插入中.
The problem is that I want to remove duplicates by col1 and col2, but also want to include to the insert all the other fields of table_1.
我尝试以这种方式添加所有相关列:
I tried to add all the relevant columns this way:
INSERT IGNORE INTO temp(M_ID,MAILING_ID,REPORT_ID,
MAILING_NAME,VISIBILITY,EXPORTED) SELECT DISTINCT
M_ID,MAILING_ID,REPORT_ID,MAILING_NAME,VISIBILITY,
EXPORTED FROM table_1
;
M_ID(int,primary),MAILING_ID(int),REPORT_ID(int),
MAILING_NAME(varchar),VISIBILITY(varchar),EXPORTED(int)
但它会将所有行插入到 temp 中(包括重复行)
But it inserted all rows into temp (including duplicates)
推荐答案
删除多列重复行最好的方法是最简单的:
The best way to delete duplicate rows by multiple columns is the simplest one:
添加唯一索引:
ALTER IGNORE TABLE your_table ADD UNIQUE (field1,field2,field3);
上面的 IGNORE 确保只保留第一个找到的行，其余的被丢弃.
The IGNORE above makes sure that only the first found row is kept, the rest discarded.
(如果您需要将来重复和/或知道它们不会再次发生，则可以删除该索引).
(You can then drop that index if you need future duplicates and/or know they won't happen again).
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