如何一次执行四个查询然后检查成功或失败？

Posted 2023-05-06

【中文标题】如何一次执行四个查询然后检查成功或失败？

【英文标题】：How to execute four queries once and then check success or failure?

【发布时间】：2015-06-15 14:59:08

【问题描述】：

我需要执行四个查询，然后如果成功必须返回 true，否则返回 false。

查询影响数据库，但函数返回 false

Private Function save_to_data()
    Dim success As Boolean = False

    Dim conn As OleDbConnection = GetDbConnection()

    Dim total_due As Decimal = sanitize(txt_total_due.Text)
    Dim amount_paid As Decimal = sanitize(txt_due.Text)
    Dim discount As Decimal = sanitize(txt_discount.Text)
    Dim balance As Decimal = sanitize(txt_balance.Text)

    Dim cmdfoods As New OleDbCommand("UPDATE foods SET status='billed' WHERE customer_id = " & lbl_id.Text & "", conn)
    Dim cmdservices As New OleDbCommand("UPDATE services SET status =  'billed' WHERE customer_id = " & lbl_id.Text & "", conn)
    Dim cmdreservations As New OleDbCommand("UPDATE reservations SET nights = 4 WHERE customerid = " & lbl_id.Text & "", conn)

    Dim bill As New OleDbCommand("INSERT INTO bills(customer_id, accomendation, food, service, total_due, amount_paid, discount, balance, transaction_date) VALUES " & _
                            "(" & lbl_id.Text & ", " & accomendation_total & ", " & food_total & ", " & service_total & ", " & total_due & ", " & amount_paid & " " & _
                            ", " & discount & ", " & balance & ", '" & Date.Now & "')", conn)


    conn.Open()
    If cmdfoods.ExecuteNonQuery And cmdservices.ExecuteNonQuery And cmdreservations.ExecuteNonQuery And bill.ExecuteNonQuery Then

        success = True
    Else
        success = False

    End If
        conn.Close()


    Return success

End Function

【问题讨论】：

在打开连接后将And 更改为AndAlso...还在每个ExecuteNonQuery 之后添加>0，因为此方法返回受影响的行数...您的方式正在评估条件不起作用，因为ExecuteNonQuery doesn't return a Boolean。

如果您的数据库支持存储过程，最好将所有四个查询放在一个中。特别是如果您需要回滚。

MS Access 2007 是否支持存储过程，我正在使用扩展名为 .accdb 的 MS Access 文件

这里的代码容易受到sql注入攻击。

@saedawke 没有用于 Access 的存储过程对不起...

【参考方案1】：

代码还有许多其他问题（sql 注入、在多个命令之间共享连接），但这是朝着正确方向迈出的一步：

Try    
    conn.Open()
    cmdfoods.ExecuteNonQuery()
    cmdservices.ExecuteNonQuery()
    cmdreservations.ExecuteNonQuery()
    bill.ExecuteNonQuery()
    success = True
Catch
    success = False
Finally
    conn.Close()
End Try

更完整的解决方案：

Private Function save_to_data()
    Dim sql As String = _
    "UPDATE foods SET status='billed' WHERE customer_id = ? ;" & _
    "UPDATE services SET status =  'billed' WHERE customer_id = ? ;" & _  
    "UPDATE reservations SET nights = 4 WHERE customerid = ? ;" 
    "INSERT INTO bills(" & _
     "customer_id, accomendation, food, service, total_due, amount_paid, discount, balance, transaction_date" & _ 
     ") VALUES ( ?, ?, ?, ?, ?, ?, ?, ?, ?);"

    Using conn As OleDbConnection = GetDbConnection(), _
          cmd As New OleDbCommand(sql, conn)

        cmd.Parameters.Add("food_customer_id", OleDbType.Integer).Value = lbl_id.Text
        cmd.Parameters.Add("serv_customer_id", OleDbType.Integer).Value = lbl_id.Text
        cmd.Parameters.Add("res_customer_id", OleDbType.Integer).Value = lbl_id.Text

        cmd.Parameters.Add("bill_customer_id", OleDbType.Integer).Value = lbl_id.Text
        cmd.Parameters.Add("accomendataion", OleDbType.VarChar).Value =  accomendation_total 
        cmd.Parameters.Add("food_total", OleDbType.Decimal).Value = food_total 
        cmd.Parameters.Add("service_total", OleDbType.Decimal).Value =  service_total 
        cmd.Parameters.Add("total_due", OleDbType.Decimal).Value = total_due 
        cmd.Parameters.Add("amount_paid", OleDbType.Decimal).Value = amount_paid 
        cmd.Parameters.Add("discount", OleDbType.Decimal).Value = discount 
        cmd.Parameters.Add("balance", OleDbType.Decimal).Value = balance 
        cmd.Parameters.Add("transaction_date", OleDbType.Date).Value =  Date.Now

        conn.Open()
        Return (cmd.ExecuteNonQuery() > 0)
    End Using  
End Function

【讨论】：

试图投票，但我必须有更多的声誉。

@Joel Coehoorn -- 如果不更新行，它会抛出异常吗？我的印象是只有在出现问题时才会触发异常。因为不满足条件而不更新行不是“问题”，对吧？

【参考方案2】：

ExecuteNonQuery 不返回布尔值，而是一个表示受插入/删除/更新语句影响的行的整数。

If cmdfoods.ExecuteNonQuery() > 0 AndAlso cmdservices.ExecuteNonQuery() > 0 AndAlso cmdreservations.ExecuteNonQuery() > 0 AndAlso bill.ExecuteNonQuery() > 0 Then
    success = True
Else
    success = False
End If

请看：https://***.com/a/5349149/3185357

【讨论】：

没有。除非我在寻找额外的信息，否则我不会阅读 cmets。我看看我是否可以回答这个问题，并看看其他人是否已经回答了。不知道这有什么价值，但对每个人来说都是如此。