MySQL中如何删除表重复记录

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创建实验表 student 表数据:
mysql use test
Database changed
mysql create table student (id int,name varchar(10));
Query OK, 0 rows affected (1.67 sec)

mysql insert into student values (11, aa
Query OK, 1 row affected (0.26 sec)

mysql insert into student values (12, aa
Query OK, 1 row affected (0.07 sec)

mysql insert into student values (13, aa
Query OK, 1 row affected (0.12 sec)

mysql insert into student values (14, aa
Query OK, 1 row affected (0.11 sec)

mysql insert into student values (15, bb
Query OK, 1 row affected (0.19 sec)

mysql insert into student values (16, bb
Query OK, 1 row affected (0.14 sec)

mysql insert into student values (17, cc
Query OK, 1 row affected (0.15 sec)

mysql select * from student;
+——+——+
| id   | name |
+——+——+
|   11 | aa   |
|   12 | aa   |
|   13 | aa   |
|   14 | aa   |
|   15 | bb   |
|   16 | bb   |
|   17 | cc   |
+——+——+
7 rows in set (0.22 sec)

方法 1:
mysql  create temporary table temp as select min(id),name from student group by name;
Query OK, 3 rows affected (0.18 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql truncate table student;
Query OK, 0 rows affected (0.40 sec)

mysql insert into student select * from temp;
Query OK, 3 rows affected (0.11 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql select * from student;
+——+——+
| id   | name |
+——+——+
|   11 | aa   |
|   15 | bb   |
|   17 | cc   |
+——+——+
3 rows in set (0.00 sec)

mysql drop temporary table temp;
Query OK, 0 rows affected (0.17 sec)

方法 2:
mysql create temporary table temp as select min(id) as MINID from student group by name;
Query OK, 3 rows affected (0.24 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql delete from student where id not in (select minid from temp);
Query OK, 4 rows affected (0.07 sec)

mysql select * from student;
+——+——+
| id   | name |
+——+——+
|   11 | aa   |
|   15 | bb   |
|   17 | cc   |
+——+——+
3 rows in set (0.00 sec)

方法 3：
mysql delete from student where id not in (select minid from (select min(id) as minid from student
group by name) b);
Query OK, 4 rows affected (0.19 sec)

mysql select * from student;
+——+——+
| id   | name |
+——+——+
|   11 | aa   |
|   15 | bb   |
|   17 | cc   |
+——+——+
3 rows in set (0.00 sec)

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