mysql on DUPLICATE KEY UPDATE test1.name=test2.name;

mysql> create table test1(id int,name varchar(5),type int,primary key(id));
Query OK, 0 rows affected (0.01 sec)
mys
mysql> create table test2(id int,name varchar(5),type int,primary key(id));
Query OK, 0 rows affected (0.01 sec)


mysql> select * from test1;
+-----+------+------+
| id  | name | type |
+-----+------+------+
| 101 | aaa  |    1 | 
| 102 | bbb  |    2 | 
| 103 | ccc  |    3 | 
+-----+------+------+
3 rows in set (0.00 sec)

mysql> select * from test2;
+-----+------+------+
| id  | name | type |
+-----+------+------+
| 201 | aaa  |    1 | 
| 202 | bbb  |    2 | 
| 203 | ccc  |    3 | 
| 101 | xxx  |    5 | 
+-----+------+------+
4 rows in set (0.00 sec)

发现重复的是更新操作。在原有记录基础上，更新指定字段内容，其它字段内容保留。例如我只想插入test2表的id,name字段，但是要保留test1表的type字段：
mysql> insert into test1(id,name,type)(select id,name,type from test2) on DUPLICATE KEY UPDATE test1.name=test2.name;
Query OK, 5 rows affected (0.04 sec)
Records: 4  Duplicates: 1  Warnings: 0

mysql> select * from test1;
+-----+------+------+
| id  | name | type |
+-----+------+------+
| 101 | xxx  |    1 | 
| 102 | bbb  |    2 | 
| 103 | ccc  |    3 | 
| 203 | ccc  |    3 | 
| 202 | bbb  |    2 | 
| 201 | aaa  |    1 | 
+-----+------+------+
6 rows in set (0.00 sec)