**：
replace into和insert into on duplicate key 區別
create table `test` (
`id` tinyint(3) unsigned not null auto_increment,
`name` char(10) not null default 」,
`dept` char(10) not null default 」,
`age` tinyint(3) unsigned not null default 『0′,
primary key (`id`),
unique key `uni_key` (`name`)
) engine=myisam auto_increment=5 default charset=latin1 |
mysql> select * from test;
| id | name | dept | age |
| 1 | wang | it | 30 |
| 2 | hong | accounting | 20 |
| 3 | gang | sales | 40 |
| 4 | raymond | service | 20 |
4 rows in set (0.00 sec)
mysql> replace into test (name,dept,age) values(『gang』,'it』,25);
query ok, 2 rows affected (0.00 sec)
mysql> select * from test;
| id | name | dept | age |
| 1 | wang | it | 30 |
| 2 | hong | accounting | 20 |
| 5 | gang | it | 25 |
| 4 | raymond | service | 20 |
4 rows in set (0.00 sec)
mysql> replace into test (name,dept,age) values(『test』,'it』,25);
query ok, 1 row affected (0.00 sec)
mysql> select * from test;
| id | name | dept | age |
| 1 | wang | it | 30 |
| 2 | hong | accounting | 20 |
| 5 | gang | it | 25 |
| 4 | raymond | service | 20 |
| 6 | test | it | 25 |
5 rows in set (0.00 sec)
mysql> replace into test (name,dept) values(『hong』,'sales』);
query ok, 2 rows affected (0.00 sec)
mysql> select * from test;
| id | name | dept | age |
| 1 | wang | it | 30 |
| 7 | hong | sales | 0 |
| 5 | gang | it | 25 |
| 4 | raymond | service | 20 |
| 6 | test | it | 25 |
5 rows in set (0.00 sec)
replace:
當沒有key衝突時，replace相當於普通的insert.
當與key衝突時，replace覆蓋相關字段，同時auto_increment累加，其它字段填充預設值，可以理解為刪除重複key的記錄，新插入一條記錄。
mysql> insert into test (name,dept,age) values(『hong』,'testing』,24)
-> on duplicate key update age=age+1;
query ok, 2 rows affected (0.00 sec)
mysql> select * from test;
| id | name | dept | age |
| 1 | wang | it | 30 |
| 7 | hong | sales | 1 |
| 5 | gang | it | 25 |
| 4 | raymond | service | 20 |
| 6 | test | it | 25 |
5 rows in set (0.00 sec)
mysql> insert into test (name,dept,age) values(『hong』,'manager』,24)
on duplicate key update age=100;
query ok, 2 rows affected (0.00 sec)
mysql> select * from test;
| id | name | dept | age |
| 1 | wang | it | 30 |
| 7 | hong | sales | 100 |
| 5 | gang | it | 25 |
| 4 | raymond | service | 20 |
| 6 | test | it | 25 |
5 rows in set (0.00 sec)
insert into …on duplicate key:
當與key衝突時，只update相應字段值。
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