违反-未找到父键错误 [英] violated - parent key not found error

问题描述

我出现以下错误:

INSERT INTO GroupMembers VALUES ('Goldfrat', 'Simon Palm')
*
ERROR at line 1:
ORA-02291: integrity constraint (SHAHA1.IAM_IS_GROUP_FK) violated - parent key 
not found 

GroupMembers 表中的约束为:

CONSTRAINT  iam_is_group_fk FOREIGN KEY(is_group) REFERENCES Members(group_name)

成员表如下:

CREATE TABLE Members (
  group_name  VARCHAR2(40),
  CONSTRAINT  g_id_pk PRIMARY KEY(group_name),
  CONSTRAINT  m_group_name_fk FOREIGN KEY(group_name) REFERENCES Artist(artistic_name));

在创建 GroupMembers 表之前，所有表都可以很好地创建.有人有主意吗?我已经抓挠了一段时间了.

All of the tables are created fine until it comes to creating the GroupMembers table. Anyone have any ideas? I've been scratching for quite a while.

推荐答案

问题是

CONSTRAINT iam_is_group_fk FOREIGN KEY(is_group)参考成员(group_name)；在group_name字段上引用表Member.

这意味着表 GroupMembers 上的字段is_group在表 Members 和 group_name 字段上必须具有相同的值.

This means that the field is_group on the table GroupMembers must have an identical value on the table Members and group_name field.

我认为这是不好的做法.首先，您应该在表GroupMembers上有一个主键字段.您不应将组成员的名称存储在表GroupMembers中，而应将其对应的ID存储在表Member中.

In my opinion this is bad practice. First of all you should have a primary key field on the table GroupMembers. You should not store the names of the group members in the table GroupMembers, but their corresponding id from the table Members.

表成员"也应如下所示:

Also the table Members, should look something like this:

    CREATE TABLE Members (
    member_id   NUMBER PRIMARY KEY
    member_name  VARCHAR2(40),
    CONSTRAINT  g_id_pk PRIMARY KEY(member_id),
    CONSTRAINT  m_group_name_fk FOREIGN KEY(group_name) REFERENCES Artist(artistic_name));

然后在表 GroupMembers 上，我想您想将一些成员关联到其组的组并返回，因此您应该执行以下操作:

Then on the table GroupMembers, I suppose you want to associate some members to their set of groups and back, so you should do something like this:

    CREATE TABLE GroupMembers (
        member_id   NUMBER,
        group_id    NUMBER
    )
    CONSTRAINT  iam_is_member_fk FOREIGN KEY(member_id) REFERENCES Members(member_id);
    CONSTRAINT  iam_is_member_fk FOREIGN KEY(group_id) REFERENCES Groups(group_id);

假设您有一个包含所有组详细信息的表 Groups ，其中主键存储为 number ，名称为group_id .

Supposing that you have a table Groups containing all the group details, with the primary key stored as number , and name group_id.

始终记住每个表必须具有主键.将此键设为数字是一种很好的做法.

Always remeber that each table must have a primary key. It is good practice for this key to be a number.

因此，通过在 Members 中具有member_id，在 Groups 中具有 group_id ，您可以在 GroupMembers中建立多对多关系.另外，在此表上放置一个唯一索引，这样就不会有重复项(同一成员多次与同一id关联).

So by having member_id in Members, group_id in Groups, you can create a many to many relationship in GroupMembers. Also, put a unique index on this table so you don't have duplicates ( the same member associated to the same id several times ).

看这个例子，将用户链接到角色.情况相同:

Look at this example linking users to roles. It is the same case:

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