我试图在同一查询中向左连接到同一表,但结果不正确,我用子查询解决了问题,这是错误的查询:
SELECT * FROM TableA ta
LEFT JOIN TableA Lta ON ta.key = Lta.key
AND ta.state IN('C')
AND Lta.state IN ('A','E')
WHERE Lta.key is null
Run Code Online (Sandbox Code Playgroud)
这就是我解决的方式
SELECT * FROM (
SELECT * FROM TableA ta
WHERE ta.state IN('C')
) AS T LEFT JOIN TableA Lta ON T.key = Lta.key
AND Lta.state in ('A','E')
WHERE Lta.key IS NULL
Run Code Online (Sandbox Code Playgroud)
如果您能给我一些与此主题相关的信息,我会对这些查询感到困惑,我将非常感谢您
谢谢
我正在尝试使用其构造函数创建对象的副本,但是当我修改副本的某些内容时,原始对象也会被修改.如果你能帮助我,我将不胜感激,这是我的代码:
public class XMLStructure
{
public XMLStructure(XMLStructure xmlCopy )
{
this.Action = xmlCopy.Action;
this.Name = xmlCopy.Name;
}
public String Name { get; set; }
public ActionXML Action { get; set; }
}
Run Code Online (Sandbox Code Playgroud)