sql 删除重复数据与查找重复数据的方法(1/4)

例1，表中有主键(可唯一标识的字段)，且该字段为数字类型

例1测试数据 /* 表结构 */
drop table if exists `t1`;
create table if not exists `t1`(
`id` int(1) not null auto_increment,
`name` varchar(20) not null,
`add` varchar(20) not null,
primary key(`id`)
)engine=innodb;

/* 插入测试数据 */
insert into `t1`(`name`,`add`) values
('abc',"123"),
('abc',"123"),
('abc',"321"),
('abc',"123"),
('xzy',"123"),
('xzy',"456"),
('xzy',"456"),
('xzy',"456"),
('xzy',"789"),
('xzy',"987"),
('xzy',"789"),
('ijk',"147"),
('ijk',"147"),
('ijk',"852"),
('opq',"852"),
('opq',"963"),
('opq',"741"),
('tpk',"741"),
('tpk',"963"),
('tpk',"963"),
('wer',"546"),
('wer',"546"),
('once',"546");

select * from `t1`;
+----+------+-----+
| id | name | add |
+----+------+-----+
| 1 | abc | 123 |
| 2 | abc | 123 |
| 3 | abc | 321 |
| 4 | abc | 123 |
| 5 | xzy | 123 |
| 6 | xzy | 456 |
| 7 | xzy | 456 |
| 8 | xzy | 456 |
| 9 | xzy | 789 |
| 10 | xzy | 987 |
| 11 | xzy | 789 |
| 12 | ijk | 147 |
| 13 | ijk | 147 |
| 14 | ijk | 852 |
| 15 | opq | 852 |
| 16 | opq | 963 |
| 17 | opq | 741 |
| 18 | tpk | 741 |
| 19 | tpk | 963 |
| 20 | tpk | 963 |
| 21 | wer | 546 |
| 22 | wer | 546 |
| 23 | once | 546 |
+----+------+-----+
23 rows in set (0.00 sec)
1 2 3 4
补充：数据库,mysql教程