Question

大家。

我相对较新的Java（一个完整的菜鸟），但有VB.Net的经验。

我正在尝试更新SQL2008表中的一行。

表名是_Registry。

当我编译下面的代码时，它失败了几个错误（在代码之后单独列出）。如果我将那段“ //这里是我遇到问题”的部分注释到catch块，它运行正常（除了表没有更新）。

非常感谢任何帮助！

public static void main(String[] args)
{
    String host = "jdbc:sqlserver://SERVER1\\Primrose;databaseName=Primrose";
    String uName = "sa";
    String uPwd = "P@ssw0rd";

// The two SQL statements I am using:

    String queryDB = "SELECT * FROM _Registry WHERE Section = 'RecIds' AND Key_ = '_Folders' AND User_ = 'sc_general'";
    String updateDB = "UPDATE _Registry SET Value WHERE RecID = 5";

// These are the 6 columns in the table named _Registry:
    int getRecId;           // RecId  [int]  IDENTITY(1,4)  
    String getUser;         // User_  [char](64)
    String getSection;      // Section [char](64)
    String getKey;          // Key_  [char](64)
    String getValue;        // Value  [char](255)
    String getExtraInfo;    // ExtraInfo  [text]

    int totalFolders = 10;  // This is a static test value that will be used to ensure I can update the table:

// Everything works from here until I exit the WHILE loop:
    try
    {
        Connection con = DriverManager.getConnection(host, uName, uPwd);
        Statement stmt = con.createStatement();

        ResultSet rs = stmt.executeQuery(queryDB);

        // Keep reading through the table until I get my desired result:
        while (rs.next())
        {
            getRecId = rs.getInt("RecId");
            getUser = rs.getString("User_");
            getSection = rs.getString("Section");
            getKey = rs.getString("Key_");
            getValue = rs.getString("Value");
            getExtraInfo = rs.getString("ExtraInfo");

            getValue = getValue.trim();    // Strip trailing spaces from string

            int newValue = Integer.parseInt(getValue) + 1;    // Convert string to number so I can add it to total folders in template
            newValue = newValue + totalFolders;    // Change to total + existing value to write back to dB
        getValue = Integer.toString(newValue);
        }

// And here is where I run into issues - I even tried
// this "rs = stmt.executeUpdate(updateDB)" but that had no effect:

        rs = stmt.executeQuery(updateDB);

        rs.updateInt( "RecId", getRecId );
        rs.updateString( "User_", getUser );
        rs.updateString( "Section", getSection );
        rs.updateString( "Key_", getKey );
        rs.updateString( "Value", getValue );
        rs.updateString( "ExtraInfo", getExtraInfo );
        rs.updateRow();

        System.out.println("Updated successfully!");
    }

    catch ( SQLException err )  
    {  
        System.out.println( err.getMessage( ) );
    }  
}

这是编译器输出：

Compiling 1 source file to C:\Java\DBupdate\build\classes

C:\Java\DBupdate\src\dbupdate\DBupdate.java:73: error: variable getRecId might not have been initialized
            rs.updateInt( "RecId", getRecId );
                                   ^

C:\Java\DBupdate\src\dbupdate\DBupdate.java:74: error: variable getUser might not have been initialized
            rs.updateString( "User_", getUser );
                                      ^

C:\Java\DBupdate\src\dbupdate\DBupdate.java:75: error: variable getSection might not have been initialized
            rs.updateString( "Section", getSection );
                                        ^

C:\Java\DBupdate\src\dbupdate\DBupdate.java:76: error: variable getKey might not have been initialized
            rs.updateString( "Key_", getKey );
                                     ^

C:\Java\DBupdate\src\dbupdate\DBupdate.java:77: error: variable getValue might not have been initialized
            rs.updateString( "Value", getValue );
                                      ^

C:\Java\DBupdate\src\dbupdate\DBupdate.java:78: error: variable getExtraInfo might not have been initialized
            rs.updateString( "ExtraInfo", getExtraInfo );
                                          ^
6 errors

C:\Java\DBupdate\nbproject\build-impl.xml:926: The following error occurred while executing this line:

C:\Java\DBupdate\nbproject\build-impl.xml:268: Compile failed; see the compiler error output for details.

BUILD FAILED (total time: 0 seconds)

Answer 1

如错误所示，您正在尝试使用可能尚未初始化的变量。尝试将它们初始化为null，或者在尝试从它们读取之前确保将它们设置为某个有用的值。

此外，您的SQL更新查询无效：您不能只SET Value，必须SET Value=并为其提供一些价值。

Answer 2

'变量可能尚未初始化'错误意味着它所说的内容。由于这些变量的声明在while循环中，如果没有从数据库返回结果会发生什么？答案：变量不会被初始化，因为while循环的主体从未执行过。尝试将这些变量声明为循环外的默认值，代码应该编译。

无法更新SQL Server数据库

2 个答案: