Question

最初我的问题是我的帖子是重复的。我相信这是因为我没有在SQL语句中链接我的表。现在我已经这样做了，我在if if.eff声明后打印出“No Data Found”。

我确信手动检查数据库中有信息，但没有成功。

这是我的代码：

<% option explicit %>
<!DOCTYPE html>
<html>
<head>

    <link rel="stylesheet" type="text/css" href="normalize.css">
</head>

<body>
<!--#include file="header.asp"-->
<!--#include file="dbconn.asp"-->



<%


    dim sql, info

'                               0                 1      2        3         4                5              
 SQL = "select projectName, UserName, Category, Created, url, Projectstable.description "&_
        "from ProjectsTable, PictureTable, Usertable, CategoryTable "&_
        "where Projectstable.ID=PictureTable.projectNum AND "&_
        "categoryNum=CategoryTable.ID AND "&_
        "ProjectsTable.userNum=Usertable.ID AND "&_
        "UserTable.ID=PictureTable.userNum "&_
            "order by Created"

set info=conn.execute(SQL)

  if info.eof then
    response.write "<p>No Data Found</p>"
  else

    do 
      response.write "<h1>" & info(0) & "</h1> By: " & info(1) & " Posted in: " & info(2) & " Created on: " & info(3) & "<br>" &_
                     "<img src=""images/" &info(4)&""">" &_
                     "<p>" & info(5) & "</p>"

      info.movenext
    loop until info.eof
  end if 

  conn.close 

%>

</body>

</html>

Answer 1

我使用ANSI 92显式连接语法而不是您使用的ANSI 89版本重写了您的查询（正如名称建议在20多年前使用显式连接替换）：

SELECT  projectName, UserName, Category, Created, url, Projectstable.description
FROM    ProjectsTable
        INNER JOIN PictureTable
            ON Projectstable.ID = PictureTable.projectNum 
        INNER JOIN Usertable
            ON UserTable.ID = PictureTable.userNum
            AND ProjectsTable.userNum = Usertable.ID
        INNER JOIN CategoryTable
            ON categoryNum = CategoryTable.ID
ORDER BY Created;

我向您突出显示，您将结果限制在图片表中的用户与项目表中的用户相同的位置。这是故意的吗？

如果删除其中一个条件，是否会获得所需的结果？所以要么

SELECT  projectName, UserName, Category, Created, url, Projectstable.description
FROM    ProjectsTable
        INNER JOIN PictureTable
            ON Projectstable.ID = PictureTable.projectNum 
        INNER JOIN Usertable
            ON UserTable.ID = PictureTable.userNum
            --AND ProjectsTable.userNum = Usertable.ID
        INNER JOIN CategoryTable
            ON categoryNum = CategoryTable.ID
ORDER BY Created;

或者

SELECT  projectName, UserName, Category, Created, url, Projectstable.description
FROM    ProjectsTable
        INNER JOIN PictureTable
            ON Projectstable.ID = PictureTable.projectNum 
        INNER JOIN Usertable
            ON ProjectsTable.userNum = Usertable.ID
            --AND UserTable.ID = PictureTable.userNum
        INNER JOIN CategoryTable
            ON categoryNum = CategoryTable.ID
ORDER BY Created;

有关ANSI 89与ANSI 92的进一步阅读，加入语法Aaron Bertrand已经写出了a great article about it的坏习惯，可以踢出系列文章。

Answer 2

答案实际上是数据库本身的错误。更明确地说，表之间的链接是不正确的。 SQL语句可能已过时但未导致错误。

Answer 3

为什么代码中存在下划线？或者第一个“'” 清理你的代码我得到：

<% option explicit %>
<!DOCTYPE html>
<html>
<head>
    <link rel="stylesheet" type="text/css" href="normalize.css">
</head>
<body>
<!--#include file="header.asp"-->
<!--#include file="dbconn.asp"-->
<%
    dim sql, info 
 SQL = "select projectName, UserName, Category, Created, url, Projectstable.description "&
        "from ProjectsTable, PictureTable, Usertable, CategoryTable "&
        "where Projectstable.ID=PictureTable.projectNum AND "&
        "categoryNum=CategoryTable.ID AND "&
        "ProjectsTable.userNum=Usertable.ID AND "&
        "UserTable.ID=PictureTable.userNum "&
            "order by Created"
set info=conn.execute(SQL)
  if info.eof then
    response.write "<p>No Data Found</p>"
  else
    do 
      response.write "<h1>" & info(0) & "</h1> By: " & info(1) & " Posted in: " & info(2) & " Created on: " & info(3) & "<br>" &
                     "<img src=""images/" &info(4)&""">" &
                     "<p>" & info(5) & "</p>"
      info.movenext
    loop until info.eof
  end if 
  conn.close 

%>
</body>
</html>

为什么ASP在我的数据库中找不到任何东西？

3 个答案: