报错信息收集

创建唯一索引时失败

语句：

create unique  index pk_name4 using BTREE  on message(name4(30) desc) comment "name4 index";

但是创建失败，返回的结果是：

Error Code: 1062. Duplicate entry '' for key 'pk_name4'

原因：

Database changed
mysql> select * from test0903.MESSAGE;
+----+----------+-----+-------+-------+-------+
| ID | MESSAGE  | id2 | name2 | name3 | name4 |
+----+----------+-----+-------+-------+-------+
|  1 | jianglei |  -1 |       |       |       |
|  2 | dengyi   |  -1 |       |       |       |
+----+----------+-----+-------+-------+-------+

该列有重复的值，所以不能创建唯一索引

结论：将name4的所有值改为不重复，即可用上述语句新建索引成功

mysql> select * from test0903.MESSAGE;
+----+----------+-----+-------+-------+----------+
| ID | MESSAGE  | id2 | name2 | name3 | name4    |
+----+----------+-----+-------+-------+----------+
|  1 | jianglei |  -1 |       |       | dengyi   |
|  2 | dengyi   |  -1 |       |       | jianglei |
+----+----------+-----+-------+-------+----------+