使用PHP在mySQL表中增加主键

Question

我正在尝试使用表单帖子向mySQL表添加行。每行都有一个主要的我正在调用quoteID。提交新表单时，它应将自身添加为表中的一行，其quoteID大于前一个quoteID。它目前看起来像这样：

<?
session_start();
if(!session_is_registered(myusername)){
header("location:login.php");
}
include 'verify.php';
$con = mysql_connect("localhost","user","$password");
if (!$con)
  {
  die('Could not connect: ' . mysql_error());
  }

mysql_select_db("internal", $con);

$previousOrderID = mysql_query("SELECT * FROM sourcingQuote ORDER BY quoteID DESC LIMIT 1"); 
$newOrderID = $previousOrderID + 1;

mysql_close($con);
?>

目前这个表中有4行，引用ID为1,2,3和4.奇怪的是，如果我尝试：

<? echo $previousOrderID; ?><br>
<? echo $newOrderID; ?><br>

输出结果为：

Resource id #3

4

无论表中有多少行，$ previousOrderID都固定为3.如何更正此问题？更重要的是，当我添加它时它是正确的，但为什么它首先输出'资源ID＃3'？

Answer 1

您可以通过选择phpmyadmin中的自动增量

来完成此操作

  

或通过sql示例，表名是demo，冒号是自动增量及其前缀键的演示

CREATE TABLE IF NOT EXISTS `demo` (
  `demmo` int(11) NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`demmo`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;

Answer 2

不，这是资源链接，您必须获取数据：

<?php
    $previousOrder = mysql_query("SELECT * FROM `sourcingQuote` ORDER BY `quoteID` DESC LIMIT 1"); 
    $previousOrder = mysql_fetch_assoc($previousOrder);
    $previousOrderID = $previousOrder['quoteID'];
    $newOrderID = $previousOrderID + 1;

    echo $previousOrderID."<br />";
    echo $newOrderID."<br />";
?>

Answer 3

避免重复的最佳方法是将QuoteID设置为AUTO_INCREMENT ed PRIMARY KEY

CREATE TABLE sourcingQuote
(
    QuoteID INT AUTO_INCREMENT,
    -- other columns,
    CONSTRAINT t_pk PRIMARY KEY (QuoteID)
)

Answer 4

你可以在mysql phpmyadmin中将'quoteID'设为自动增量.....

并且你获得了资源ID＃3 ..因为你正在引用资源链接.. 你可以通过

打印数据

$previousOrderID = mysql_query("SELECT * FROM sourcingQuote ORDER BY quoteID DESC LIMIT 1"); 
$previousOrderID = mysql_fetch_assoc($previousOrderID);
$newOrderID = $previousOrderID['ID'] + 1;