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当我在 Oracle 中运行以下 SQL 时，会正确报告列默认值（“测试”）。当我在 .NET 中运行相同的 SQL 时，报告的默认值为 NULL：

SELECT column_name, data_default FROM user_tab_columns WHERE table_name='MYTABLENAME'

有问题的列是 Varchar2。我还测试了一个数字列 - 同样的问题。

数据库版本是 Oracle Database 11g Express Edition Release 11.2.0.2.0 - Production

.NET 连接器是 ODP.NET

操作系统是 Windows 7 / 64

我从 all_tab_columns 得到相同的结果（NULL）

.NET 代码：

Dim provider As DbProviderFactory = DbProviderFactories.GetFactory("Oracle.DataAccess.Client")
Using connection As DbConnection = provider.CreateConnection
  connection.ConnectionString = "Data Source=localhost; User Id=userid; Password=password"
  connection.Open
  Using dt As New DataTable
    Using command As DbCommand = provider.CreateCommand
      command.CommandText = "SELECT column_name, data_default FROM user_tab_columns WHERE table_name='MYTABLENAME'"
      command.Connection = connection
      Using da As DbDataAdapter = provider.CreateDataAdapter
        da.SelectCommand = command
        da.Fill(dt)
      End Using
    End Using
    For Each row As DataRow in dt.Rows
      Response.Write(row("COLUMN_NAME") & " " & row("DATA_DEFAULT") & "<br>")
    Next
  End Using
End Using
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2 回答 2

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data_default 是 Oracle 类型的 LONG。通过本文档http://docs.oracle.com/html/B14164_01/featData.htm#i1007197看来您需要做一些特殊的工作来检索 LONG 值。

于 2013-03-29T16:15:49.183 回答
0

我最终创建了一个 Oracle 函数来处理这个问题：

CREATE OR REPLACE 
  FUNCTION GetColumnDefaultValue(
    TableName IN varchar2,
    ColumnName IN varchar2
  )
  RETURN varchar2
    AS ddLong long; 
    BEGIN
      SELECT data_default
      INTO ddLong
      FROM user_tab_columns
      WHERE table_name = TableName
        AND column_name = ColumnName;
    RETURN
      substr(ddLong,0,255);
    END;

The default value is retrieved using:

SELECT GetColumnDefaultValue('TABLENAME','FIELDNAME') FROM dual

Note that this retrieves only the first byte of the default value. Modify substr(ddLong,0,255); to return more.

于 2013-03-29T21:00:35.227 回答