Oracle data_default返回long

Question

我正在尝试获取列的默认值，但遗憾的是我什么都没得到。 这是我的代码：

'ColumnName is the Column Name in question
'BaseTableName is the Table Name
   Dim myCon As New OracleConnection
   myCon.ConnectionString = gApp.ConnectString
   myCon.Open()
   Dim myCmd As New OracleCommand
   myCmd.Connection = myCon
   myCmd.CommandType = CommandType.Text
   myCmd.CommandText = "select data_default " & _
          "from all_tab_columns " & _
          "where table_name='" & BaseTableName & "' " & _
          "and column_name='" & ColumnName & "'"
   Dim dr As OracleDataReader
   dr = myCmd.ExecuteReader
   dr.Read()
   Dim val = dr.GetValue(0).ToString

   '  Dim val = myCmd.ExecuteScalar 'I tried also with executeScalar but it was the same

   myCon.Close()

当我在oracle中执行相同的字符串时，它返回一个Long，而long内部则是默认值

如何在长篇内获得原始值？

Answer 1

假设问题是因为您的环境不支持LONG，您可以创建一个函数来首先将值转换为VARCHAR2。例如：

create table test1(a number default 0);

create or replace function get_data_default(
    p_owner varchar2,
    p_table_name varchar2,
    p_column_name varchar2
) return varchar2 is
    v_data_default varchar2(4000);
begin
    select data_default
    into v_data_default
    from all_tab_columns
    where owner = p_owner
        and table_name = p_table_name
        and column_name = p_column_name;

    return v_data_default;
end;
/

select get_data_default(USER, 'TEST1', 'A') from dual;

0

如果您对其他列有此问题，可以使该函数更通用，或者您可以查看实用程序以将所有字典LONG转换为CLOB。 Dictionary Long Application可以做到这一点，虽然它会变得非常复杂。