访问 SQL 随机发生器未按预期工作

Access SQL Randomizer Not working as intended

我正在使用下面提到的代码 select 来自 Access 数据库的记录 ID,该记录 ID 在最后一天尚未 select 编辑并将其添加到数组中。

总的目标是检索符合初始 "Difficulty" 条件的记录,只要该记录之前从未 select 编辑过或上次未选择该记录2天。循环完成后,我应该有 x 数量的唯一记录 ID,并将它们添加到数组中以便在其他地方处理。

 Private Function RetrieveQuestionID(questionCount As Integer)

    ' We're using this retrieve the question id's from the database that fit our arrangements.
    Dim intQuestArray(0 To questionCount) As Integer
    Dim QuestionConnection As New OleDb.OleDbConnection("PROVIDER=Microsoft.ACE.OLEDB.12.0;Data Source = |DataDirectory|\Database\MillionaireDB.accdb;")

    QuestionConnection.Open()

    For i As Integer = 1 To intNoOfQuestions
        'TODO: If there are no valid questions, pull up any of them that meets the difficulty requirement....

        Dim QuestionConnectionQuery As New OleDb.OleDbCommand("SELECT Questions.QuestionID FROM Questions WHERE (((Questions.QuestionDifficulty)=[?])) AND (((Questions.LastDateRevealed) Is Null)) OR (Questions.LastDateRevealed >= DateAdd('d',-2,Date())) ORDER BY Rnd((Questions.QuestionID) * Time());", QuestionConnection)
        QuestionConnectionQuery.Parameters.AddWithValue("?", intQuestionDifficulty(i - 1).ToString)
        Dim QuestionDataAdapter As New OleDb.OleDbDataAdapter(QuestionConnectionQuery)
        Dim QuestionDataSet As New DataSet

        QuestionDataAdapter.Fill(QuestionDataSet, "Questions")
        intQuestArray(i - 1) = QuestionDataSet.Tables("Questions").Rows(0).Item(0)

        Dim QuestionConnectionUpdateQuery As New OleDb.OleDbCommand("UPDATE Questions SET Questions.LastDateRevealed = NOW() WHERE Questions.QuestionID = [?]", QuestionConnection)
        QuestionConnectionUpdateQuery.Parameters.AddWithValue("?", intQuestArray(i - 1).ToString)
        QuestionConnectionUpdateQuery.ExecuteNonQuery()

    Next

    QuestionConnection.Close()
    Return intQuestArray
End Function

但是,遍历数组将显示即使记录在循环期间更新,也会以某种方式重复记录。

是否有另一种方法可以循环遍历数据库并提取这些记录?我什至试图将 .Open().Close() 语句移动到 For...Next 循环中,结果比以前更糟。

正如史蒂夫所写,>= 应该是 < .

此外,您的 WHERE 子句缺少 OR 部分周围的括号。 它应该是(没有所有不必要的括号):

SELECT Questions.QuestionID 
FROM Questions 
WHERE Questions.QuestionDifficulty=[?] 
  AND ( Questions.LastDateRevealed Is Null 
     OR Questions.LastDateRevealed < DateAdd('d',-2,Date()) ) 
  ORDER BY Rnd(Questions.QuestionID * Time());

另请参阅 How to get random record from MS Access database - 建议使用负值作为 Rnd() 的参数。