需要从 mysql 帮助编译的数组

Question

这一直困扰着我，我无法理解它。我将使用食品类比来尝试简化我的问题。

1000 名公众成员被要求从 13 种类型的脚垫中选择一种。这些选择然后根据他们的名字存储在一个 mysql 数据库中。

e.g.    billy   mary   etc.   etc.

milk....semi. .skimmed...

bread...white...brown....

cheese..edam.....edam....

fruit...apple...orange...

veg....potato...sprout...

meat....beef.....beef....

sweet..bonbons..liquorice..

fish...trout....salmon...

crisp....s&v....plain....

biscuit..hovis..rich tea..

wine.....red.....red.....

beer....stella..carlsburg..

carb....coke.....pepsi....

然后要求这 1000 人中的一个通过复选框选择从零到 13 的任意选项。

通过搜索数据库，有多少其他人选择了相同的品种？

在表格中显示他们的所有名字以及他们为所有 13 个品种选择的内容。

这有意义吗？我希望如此，因为它让我发疯。

Answer 1

部分答案：

• 通过排序和连接组成一组线性选择
• 然后比较变成一个简单的 WHERE 子句

所以您首先要进行计算，将字符串放入某个字段，如字面意思“milk|semi|skimmed”。

Answer 2

假设你有一个简单的布局，那么你会有这样的东西（我将自己限制在三个类别中）：

PersonId  What_Milk  What_Bread  What_Cheese
       1  Semi       Wheat       Swiss
       2  Skimmed    Rolls       French
       3  Soy        Brown       Smelly
       4  Low Fat    Wheat       Swiss

如果我理解正确，你的问题是这样的：

当第 4 个人被要求选择 0 .. 3 个她的食物时，她可以选择“面包”和“奶酪”复选框，这意味着查询应该产生第 1 个人作为匹配项。对吧？

SELECT
  PersonId,
  What_Milk,
  What_Bread,
  What_Cheese
FROM
  FoodPreference
WHERE
  PersonId != ?
  AND What_Milk   = IFNULL(NULLIF(?, ''), What_Milk)
  AND What_Bread  = IFNULL(NULLIF(?, ''), What_Bread)
  AND What_Cheese = IFNULL(NULLIF(?, ''), What_Cheese)

您的复选框值稍后将转到问号占位符所在的位置。 （我已经用 IFNULL/NULLIF 替换了以前的 CASE WHEN 结构，它具有相同的效果，但对 PHP 准备语句更友好。）

如果未选中复选框（从而将值固定为某物），则将相应的列与其自身进行比较。这意味着它的值不会影响结果。如果其他列匹配，则将选择该行。

这也意味着如果用户选择了零个复选框，所有行将被返回。一个人选择的食物越多，匹配就越接近。

在 PHP 中，我建议您使用 mysqli_prepare() 从查询字符串创建准备好的语句，并使用 mysqli_stmt_bind_param() 将实际值绑定到问号占位符。这比直接构建 SQL 字符串要安全得多。 PHP documentation has a whole lot of info on mysqli，看看吧。

Answer 3

SELECT  
    PersonId,  
    milk,  
    bread,  
    cheese
FROM  FoodPreference
WHERE  PersonId != :chosen_person_id  
    AND $milk= CASE WHEN :isset($_POST["milk"]))> '' THEN :isset($_POST["milk"]))   ELSE milk END  
    AND $bread= CASE WHEN :isset($_POST["bread"]))> '' THEN :isset($_POST["bread"]))  ELSE bread END  
    AND $cheese= CASE WHEN :isset($_POST["cheese"]))> '' THEN :isset($_POST["cheese"])) ELSE cheese END

我走对了吗？

Answer 4

好的，我发布了一个回复，但 Tomalak 非常正确地指出了一个逻辑缺陷。我再试一次：

将类别列为 13 列的替代方法是将它们列为表中的 13 行，如下所示：

CREATE TABLE FoodPreference (
  PersonID   INT NOT NULL REFERENCES People,
  FoodCat    VARCHAR(10) NOT NULL REFERENCES FoodCategories,
  FoodChoice VARCHAR(10) NOT NULL,
  PRIMARY KEY (PersonID, FoodCat)
);
INSERT INTO FoodPreference VALUES
  (123, 'bread', 'white'),
  (123, 'milk', 'skim'),
  (123, 'cheese', 'edam'), ...
  (321, 'bread', 'brown'),
  (321, 'milk', 'whole'),
  (321, 'cheese', 'edam'), ...

然后您可以使用如下查询，将所选人 (p1) 中的任何行与另一个人 (p2) 的具有相同食物选择的行匹配，然后再匹配该人的所有其他选择 (p3 ):

SELECT DISTINCT p3.*
FROM FoodPreference AS p1
  JOIN FoodPreference AS p2 
    ON (p1.FoodCat = p2.FoodCat AND p1.FoodChoice = p2.FoodChoice 
      AND p1.PersonID != p2.PersonID)
  JOIN FoodPreference AS p3 
    ON (p2.PersonID = p3.PersonID AND p2.FoodCat != p3.FoodCat)
WHERE p1.PersonID = {(int)$chosen_person_id}
  AND p1.FoodCat IN ('milk', 'bread', 'cheese');

WHERE 子句中的列表 'milk', 'bread', 'cheese' 是您需要根据应用程序中的 $_POST 变量在 PHP 代码中构建的内容。如果选中了一个复选框，请在列表中包含该食物类别。

<?php
$food_cat_array = array("'none'");
$legal_food_cats = array('milk'=>1, 'bread'=>1, 'cheese'=>1, ...);
foreach (array_intersect_key($_POST, $legal_food_cats) as $key => $checked) {
  if ($checked) {
    $food_cat_array[] = "'$key'"; 
  }
}
$in_predicate = join(',', $food_cat_array);

Answer 5

$sql = mysql_query("        
    SELECT  
    *
    FROM  ".$prefix."_users
    WHERE  username !='$username'  
    AND req_country   = IFNULL(NULLIF($bcountry, ''), req_country)  
    AND req_region  = IFNULL(NULLIF($bregion, ''), req_region)  
    AND req_type = IFNULL(NULLIF($btype, ''), req_type)
    AND req_beds = IFNULL(NULLIF($bbeds, ''), req_beds)
    AND req_value = IFNULL(NULLIF($bvalue, ''), req_value)
    AND country   = IFNULL(NULLIF($scountry, ''), country)  
    AND region  = IFNULL(NULLIF($sregion, ''), region)  
    AND type = IFNULL(NULLIF($stype, ''), type)
    AND beds = IFNULL(NULLIF($sbeds, ''), beds)
    AND value = IFNULL(NULLIF($svalue, ''), value)
    AND pool = IFNULL(NULLIF($spool, ''), 'Yes')
    AND garage = IFNULL(NULLIF($sgarage, ''), >0) 
            AND disabled = IFNULL(NULLIF($sdisabled, ''), 'Yes')");
$num = mysql_num_rows($sql);
echo "Total matches ($num): <br><br>";
        while($row = mysql_fetch_array($sql)){...etc

Answer 6

case "display_results":

if ($bcountry = !isset($_POST["bcountry"])){
      $bcountry = "No";
      }else {
      $bcountry = "Yes";
      }
if ($bregion = !isset($_POST["bregion"])){
      $bregion = "No";
      }else {
      $bregion = "Yes";
      }
if ($btype = !isset($_POST["btype"])){
      $btype = "No";
      }else {
      $btype = "Yes";
      }
if ($bbeds = !isset($_POST["bbeds"])){
      $bbeds = "No";
      }else {
      $bbeds = "Yes";
      }
if ($bvalue = !isset($_POST["bvalue"])){
      $bvalue = "No";
      }else {
      $bvalue = "Yes";
      }
if ($scountry = !isset($_POST["scountry"])){
      $scountry = "No";
      }else {
      $scountry = "Yes";
      }
if ($sregion = !isset($_POST["sregion"])){
      $sregion = "No";
      }else {
      $sregion = "Yes";
      }
if ($stype = !isset($_POST["stype"])){
      $stype = "No";
      }else {
      $stype = "Yes";
      }
if ($sbeds = !isset($_POST["sbeds"])){
      $sbeds = "No";
      }else {
      $sbeds = "Yes";
      }
if ($svalue = !isset($_POST["svalue"])){
      $svalue = "No";
      }else {
      $svalue = "Yes";
      }
if ($spool = !isset($_POST["spool"])){
      $spool = "No";
      }else {
      $spool = "Yes";
      }
if ($sgarage = !isset($_POST["sgarage"])){
      $sgarage = "No";
      }else {
      $sgarage = "Yes";
      }
if ($sdisabled = !isset($_POST["sdisabled"])){
      $sdisabled = "No";
      }else {
      $sdisabled = "Yes";
      }

     $result = mysql_query("SELECT * FROM  ".$prefix."_users WHERE  username!='$username' 
AND (('$bcountry'='Yes' AND req_country= '$country') OR ('$bcountry'='No')) 
AND (('$bregion'='Yes' AND req_region= '$region') OR ('$bregion'='No'))
AND (('$btype'='Yes' AND req_type= '$type') OR ('$btype'='No'))
AND (('$bbeds'='Yes' AND req_beds= '$beds') OR ('$bbeds'='No'))
AND (('$bvalue'='Yes' AND req_value= '$value') OR ('$bvalue'='No'))
AND (('$scountry'='Yes' AND country= '$req_country') OR ('$scountry'='No'))
AND (('$sregion'='Yes' AND region= '$req_region') OR ('$sregion'='No'))
AND (('$stype'='Yes' AND type= '$req_type') OR ('$stype'='No'))
AND (('$sbeds'='Yes' AND beds= '$req_beds') OR ('$sbeds'='No'))
AND (('$svalue'='Yes' AND value= '$req_value') OR ('$svalue'='No'))
AND (('$spool'='Yes' AND pool= 'Yes') OR ('$spool'='No'))
AND (('$sgarage'='Yes' AND garage>=1 ) OR ('$sgarage'='No'))
AND (('$sdisabled'='Yes' AND disabled= 'Yes') OR ('$sdisabled'='No'))
")or die("MySQL ERROR: ".mysql_error());
$number = mysql_num_rows($result);