使用spring，hibernate在mysql中创建数据库表时出错

Question

@Entity
@Table(name = "RMS_USER_UPDATE", uniqueConstraints = { 
@UniqueConstraint(columnNames = "UPDATE_ID") })
public class UserUpdateData implements Serializable {
private static final long serialVersionUID = 1L;

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "UPDATE_ID", unique = true, nullable = false)
private long updateId;


@Column(name = "USER_ID", unique = false, nullable = true)
private long userId;

@Column(name = "CNAME", unique = false, nullable = true)
private String cname;

@Column(name = "BALANCE_AMOUT ", unique = false, nullable = true)
private double balanceAmnt;

这是我的实体类。我没有使用任何类型的映射，但 USER_ID 列对于其他一些表是通用的。当我运行代码时，显示 BALANCE_AMOUT 的重复列名称错误。 错误是，

[ERROR] 2017-08-04 07:18:AM [org.hibernate.tool.hbm2ddl.SchemaUpdate] 
[execute : 236] - HHH000388: Unsuccessful: alter table RMS_USER_UPDATE add 
column BALANCE_AMOUT  double precision
[ERROR] 2017-08-04 07:18:AM [org.hibernate.tool.hbm2ddl.SchemaUpdate] 
[execute : 237] - Duplicate column name 'BALANCE_AMOUT'

当我更改 BALANCE_AMOUT 的列名时，错误消失了。为什么会这样？我没理由。有人可以帮忙吗？