MySQL`INSERT INTO SELECT`子句在唯一字段

Question

我使用INSERT INTO SELECT跨数据库迁移用户数据，但会生成

Duplicate entry '                  　' for key 'users_name_unique'

虽然数据源是另一个唯一索引，但不应包含任何重复数据。（'users_name_unique'是db2.users上的索引名称）

这是查询，其中db2.users的name字段是varchar（50）唯一且不是null索引，db1.users中的name字段是varchar（60）唯一而不是null索引。我已经检查了每个记录中字段的长度，长度都小于50。

INSERT INTO db2.users (name, email, uid) SELECT
    name,
    IF (mail = '', NULL, mail) AS email,
    uid
FROM
    db1.users;

db1.users的名称字段中有不可打印或空格。

可能是什么问题？

更新

我创建了多个测试表，如下所示，有两个表具有非常相似的结构且没有数据（由于源数据是varchar（60），我故意改变了长度），但结果不同。

    mysql> desc ttt3;
+-------+-------------+------+-----+---------+----------------+
| Field | Type        | Null | Key | Default | Extra          |
+-------+-------------+------+-----+---------+----------------+
| id    | int(11)     | NO   | PRI | NULL    | auto_increment |
| name  | varchar(50) | NO   | UNI | NULL    |                |
+-------+-------------+------+-----+---------+----------------+
2 rows in set (0.01 sec)

mysql> desc users;
+-------+------------------+------+-----+---------+----------------+
| Field | Type             | Null | Key | Default | Extra          |
+-------+------------------+------+-----+---------+----------------+
| id    | int(10) unsigned | NO   | PRI | NULL    | auto_increment |
| name  | varchar(60)      | NO   | UNI | NULL    |                |
+-------+------------------+------+-----+---------+----------------+
2 rows in set (0.01 sec)

mysql> show index from ttt3;
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| ttt3  |          0 | PRIMARY  |            1 | id          | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
| ttt3  |          0 | name     |            1 | name        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
2 rows in set (0.00 sec)

mysql> show index from users;
+-------+------------+-------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name          | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+-------+------------+-------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| users |          0 | PRIMARY           |            1 | id          | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
| users |          0 | users_name_unique |            1 | name        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
+-------+------------+-------------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
2 rows in set (0.00 sec)

mysql> insert into ttt3(name) select name from scratch.users where scratch.users.uid != 0;
Query OK, 1556 rows affected (0.24 sec)
Records: 1556  Duplicates: 0  Warnings: 0

mysql> insert into users(name) select name from scratch.users where scratch.users.uid != 0;
ERROR 1062 (23000): Duplicate entry '                  　' for key 'users_name_unique'

更新

事实证明，目标字段的排序规则设置为'utf8_unicode_ci'，原始字段为'utf8_general_ci'，更改此选项可解决问题。

Answer 1

原因如下：

目标字段的排序规则设置为＆quot; utf8_unicode_ci＆＃39; （laravel的默认排序规则）和原始字段是'utf8_general_ci＆＃39;。

这些排序规则有不同的排序规则＆＃34;排序＆＃34;或＆＃34;等于＆＃34;。更改此选项解决了问题。