MySQL：有什么方法可以让列默认为自动增量（或从自动增量字段复制）但仍然允许插入其他值？

发布于 2024-11-01 00:47:46 字数 812 浏览 0 评论 0原文

我正在建立一个问答网站。我想将问题和答案存储在同一个表中：

CREATE TABLE Q_n_A (
    id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    question_id INT NOT NULL,
    # type indicates whether the record is a question (1) or an answer (0)
    type BOOL,
    title VARCHAR(80),
    body VARCHAR(5000)
);

当我插入新问题时，我没有该新问题的 question_id 值。因此，我想使用 id 的 auto_incremented 值作为 question_id 的值。因此，在这种情况下，我希望 question_id 默认为 AUTO_INCRMENT 或从 id 复制。

当我插入现有问题的答案时，我已经知道该答案的 question_id 是什么。因此，我想在插入时指定 question_id 的值。

有没有办法在这里做我想做的事：默认 question_id 为 AUTO_INCRMENT （或从 AUTO_INCRMENT 字段 id 复制>) 但仍然允许指定 question_id 的非默认值？

谢谢。

原文

I'm building a Q&A site. I want to store both questions and answers in the same table:

CREATE TABLE Q_n_A (
    id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    question_id INT NOT NULL,
    # type indicates whether the record is a question (1) or an answer (0)
    type BOOL,
    title VARCHAR(80),
    body VARCHAR(5000)
);

When I insert a new question, I don't have a value of question_id for this new question. As such, I want to use the auto_incremented value of id as the value for question_id. So in this case I want question_id to either default to AUTO_INCREMENT or to copy from id.

When I insert an answer to an existing question, I already know what is the question_id for that answer. As such I want to specify a value for question_id at the insert.

Is there a way to do what I want here: default question_id to AUTO_INCREMENT (or copy from the AUTO_INCREMENT field id) but still allow non-default value of question_id to be specified?

Thanks.

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乄_柒ぐ汐 2024-11-08 00:47:46

CREATE TABLE Q_n_A (
overall_id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
parent_id INT default '0',
title VARCHAR(80),
body VARCHAR(5000)
);

现在，当有人询问时，只需不插入parent_id，就会导致parent_id = 0
当有人回答时，通过 $_POST 数据或您的表单设置方式将 ovverall_id 插入到 Parent_id 中。

轻松查询给定问题的正确答案

CREATE TABLE Q_n_A (
overall_id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
parent_id INT default '0',
title VARCHAR(80),
body VARCHAR(5000)
);

Now when someone ask simply insert no parent_id, resulting it to have parent_id = 0
When someone answers insert into parent_id the ovverall_id, via $_POST data or however your form is setup.

Making it easy to query the correct answers to the given question

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