1.Consider an employee database as shown in figure 4.12. Write a query to find the ID of an employee who does not have a manager. Note that the employee who will not have manager will be an employee ID that is not present in the manages table.

Sure, here's a SQL query to find the ID of an employee who does not have a manager:

SELECT e.ID
FROM employee e
LEFT JOIN manages m ON e.ID = m.employeeID
WHERE m.managerID IS NULL;

Explanation:

- We start by selecting the ID column from the employee table.
- We then use a LEFT JOIN to join the employee table with the manages table on the employeeID column from the employee table and the ID column from the manages table.
- We add a condition to only return rows where the managerID column from the manages table is NULL, indicating that the employee does not have a manager.
- This will return the ID of all employees who do not have a manager, which is what we're looking for.

相关问题

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MinIO是一个开源的对象存储服务器，它兼容Amazon S3云存储服务的API。它可以在本地或者私有云环境中部署，提供高性能、高可用性的对象存储服务。

MinIO的主要特点包括：
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这个错误提示是由于XML文件缺少与之关联的样式信息导致的。在浏览器中打开XML文件时，如果没有指定样式信息，浏览器无法正确地显示XML内容。下面是一些可能的解决方法：
1. 确保XML文件中包含正确的样式信息。可以通过在XML文件中添加CSS或XSLT样式表来定义样式。
2. 检查XML文件是否正确引用了样式表。可以在XML文件中使用<?xml-stylesheet?>指令来引用外部样式表。
3. 确保浏览器支持XML样式表。不同的浏览器对XML样式表的支持程度可能有所不同，可以尝试在其他浏览器中打开XML文件。
4. 如果以上方法都无效，可以尝试将XML文件转换为其他格式，如HTML，以便在浏览器中正确显示。