翻译 A relational store has been configured without specifying either the DbConnection or connection string to use

这意味着在配置关系数据存储时，没有指定用于使用的 `DbConnection` 或连接字符串。这可能会导致数据存储无法正常工作，因为系统无法确定如何连接到数据库。应该指定一个 `DbConnection` 对象或连接字符串，以便系统能够正确连接到数据库。

相关问题

Failed to determine a suitable R2DBC Connection URL

"Failed to determine a suitable R2DBC Connection URL"是一个错误消息，通常在使用R2DBC（Reactive Relational Database Connectivity）连接数据库时出现。这个错误消息表示无法确定适合的R2DBC连接URL。

要解决这个问题，你可以尝试以下几个步骤：

1. 检查数据库依赖：确保你的项目中已经添加了正确的R2DBC数据库依赖项。例如，如果你使用PostgreSQL数据库，你需要添加相应的R2DBC PostgreSQL依赖项。

2. 检查连接URL：确认你提供的数据库连接URL是否正确。这个URL包含了连接数据库所需的信息，如主机名、端口号、数据库名称等。确保URL中的信息与你的数据库配置相匹配。

3. 检查数据库权限：确保你提供的数据库用户具有足够的权限来连接和操作数据库。如果权限不足，你可能需要更新数据库用户的权限或者使用具有足够权限的用户来连接数据库。

4. 检查网络连接：如果你的应用程序和数据库位于不同的主机上，请确保网络连接正常，并且可以从应用程序主机访问到数据库主机。

5. 检查数据库状态：确保数据库正在运行，并且可以接受来自应用程序的连接请求。如果数据库处于离线状态或者无法接受连接，你需要确保数据库正确配置并已启动。

create a relational database schema with SQL statement.

Sure, here is an example of creating a simple relational database schema for a blog website using SQL:

CREATE TABLE users (
  id INT PRIMARY KEY,
  username VARCHAR(50) NOT NULL,
  email VARCHAR(100) NOT NULL,
  password VARCHAR(100) NOT NULL
);

CREATE TABLE posts (
  id INT PRIMARY KEY,
  title VARCHAR(255) NOT NULL,
  content TEXT NOT NULL,
  author_id INT NOT NULL,
  FOREIGN KEY (author_id) REFERENCES users(id)
);

CREATE TABLE comments (
  id INT PRIMARY KEY,
  content TEXT NOT NULL,
  post_id INT NOT NULL,
  author_id INT NOT NULL,
  FOREIGN KEY (post_id) REFERENCES posts(id),
  FOREIGN KEY (author_id) REFERENCES users(id)
);

In this example, we have three tables: "users", "posts", and "comments". The "users" table stores information about registered users, including their username, email, and password. The "posts" table stores information about blog posts, including the title, content, and the ID of the user who wrote the post. The "comments" table stores information about comments on blog posts, including the content of the comment, the ID of the post it refers to, and the ID of the user who wrote the comment.

Note that we have also included foreign key constraints in the "posts" and "comments" tables, which ensure that the "author_id", "post_id", and "author_id" fields reference valid IDs in the "users" and "posts" tables, respectively.