小编Car*_*doc的帖子

我有这个代码:

Function Get_Control_Station_Address(counter As Integer)
    Check_DB_Con() 'Check if the connection is okay
    SQL_Query = "SET @row_number = 0; " _
                & "SELECT hardware_add " _
                & "FROM (" _
                    & "SELECT " _
                    & "@row_number:=@row_number + 1 AS num, " _
                    & "hardware_add AS hardware_add " _
                    & "FROM teller_info" _
                & ") AS sub_query " _
                & "WHERE num = " & counter & ";"

    Dim MySQL_CMD As New MySqlCommand(SQL_Query, MysqlConn)

    Try
        MySQL_CMD.Connection.Open()
        MySQL_Reader = MySQL_CMD.ExecuteReader()

        While MySQL_Reader.Read
            MySQL_Result …

SELECT
  items.item_id, items.category_id, items.title, items.description, items.quality,
  items.type, items.status, items.price, items.posted, items.modified,
  zip_code.state_prefix, zip_code.city, books.isbn13, books.isbn10, books.authors,
  books.publisher
FROM
(
  (
    items
    LEFT JOIN bookitems ON items.item_id = bookitems.item_id
  )
  LEFT JOIN books ON books.isbn13 = bookitems.isbn13
)
LEFT JOIN zip_code ON zip_code.zip_code = items.item_zip
WHERE items.rid = $rid`

我正在运行此查询以获取用户项目及其位置的列表.zip_code表有超过40k的记录,这可能是问题所在.目前最多需要15秒才能返回大约20个项目的列表!我该怎么做才能使这个查询更有效率？

更新:以下是相关表的表创建代码.抱歉格式化!

CREATE TABLE `bookitems` (  
    `bookitem_id` int(10) unsigned NOT NULL auto_increment COMMENT 'BookItem ID',  
    `item_id` int(10) unsigned NOT NULL default '0' COMMENT 'Item ID',  
    `isbn13` varchar(13) NOT NULL default '' COMMENT …

我有什么理由不能在HTML标签内插入注释吗？

示例:在HTML中(不可能)

 <img <!-- sample comment--> src="" alt="Sample Picture" class="img-circle center-block" />

在JavaScript中,它可以很容易地完成.

示例:在JS中(可能)

verticalCentered: /* Sample Comment*/ true

请详细解释.

如何将一个类中的共享函数调用到另一个类,这是我的代码,

Imports System.Web.UI

Public Class functest
    Public Shared Function callthis(source as object, args as event)
      'code goes here
    End Function
End Class

我必须在另一个类中调用"callthis"函数.我该怎么做？

我有两个场景涉及使用My.Settings.sampleSettingsa dataType boolean和a sampleVariableas data type boolean.

代码:由于sampleVariable和sampleSettings都是boolean,我就这样声明它们

Dim sampleVariable As Boolean = My.Settings.sampleSettings
Console.WriteLine("Result: " & sampleVariable)
If sampleVariable = False Then
    Console.WriteLine("1")
    sampleVariable = True
Else
    Console.WriteLine("2")
    sampleVariable = False
End If
My.Settings.Save()

输出:输出似乎不满足条件1,它总是满足条件2是假的

Result: False
1
Result: False
1
Result: False
1

代码:在这段代码中,我没有将sampleSettings放到一个布尔变量中,它运行正常.

Console.WriteLine("Result: " & My.Settings.sampleSettings)
If My.Settings.sampleSettings = False Then
    Console.WriteLine("1")
    My.Settings.sampleSettings = True
Else
    Console.WriteLine("2")
    My.Settings.sampleSettings = False
End If
My.Settings.Save()

输出:每当我点击按钮时它会触发不同的条件,这是我的目标.

Result: False
1 …