This is what your sql query should look like
INSERT INTO [SOME_TABLE]
([Position]
,[DisplayText]
,[DisplayURL]
,[ToolTip])
VALUES (SELECT Position, DisplayText, Display, URLToolTip
FROM [SOME_OTHER_TABLE]
WHERE [Position] = @parent_id)
The value for the where clause should be a parameter in your c# code.
SqlParameter param = new SqlParameter
{
ParameterName = "@parent_id",
DbType = DbType.Int32,
Value = parentID
};
and added to your SqlCommand object like this
cmd.Parameters.Add(param);