在MySQL Query中加入表而不是多个查询

Question

我有这个问题

$query = "SELECT * FROM items WHERE itemStatus = '1' AND itemAdded > '$timestamp'";

一旦这个查询返回结果，我就会遍历结果

结果数组是itemID，itemLocationID，categoryParentID，categoryID，itemName，itemDetails

在循环期间，我通过调用同一个类中的函数来运行其他三个查询

$locationName = $this->getLocationByName($locationID);
$categoryParentName = $this->getCategoryByName($categoryParentID);
$categoryName = $this->getCategoryByName($categoryID);

函数getLocationByName执行此查询;

$q = mysql_query("SELECT * FROM locations WHERE locationID = '$locationID'");

这将返回locationID，locationName，locationLink的数组

函数getCategoryByName执行此查询;

$q = mysql_query("SELECT * FROM categories WHERE categoryID = '$categoryID'");

这将返回categoryID，categoryName，categoryLink的数组

有人可以帮我优化这个查询，也许可以加入他们来保存这么多查询。

提前致谢。

我现在正在使用此查询

$q = mysql_query("SELECT 
i.itemID, 
i.locationID,
i.categoryParentID,
i.categoryID, 
i.itemName,
i.itemDetails,
l.*,
c.*        

FROM项目i内部联接位置l on i.locationID = l.locationID内部联接类别c on i.categoryID = c.categoryID WHERE itemStatus ='1'AND itemAdded>'$ timestamp'“）或die（mysql_error（））;

结果是

Array

（[itemID] => 81300 [locationID] => 17 [categoryParentID] => 21 [categoryID] => 183 [itemName] => blah [itemDetails] => blah [locationName] =>很棒它按预期拉入位置。[locationLink] => blah [categoryName] =>辉煌它按预期拉入类别。[categoryLink] => blah）

[categoryName] => //these are missing for categoryParentID
[categoryLink] => //these are missing for categoryParentID

Answer 1

我认为应该类似于下面的查询。 我没看到你在哪里使用$ categoryParentName。

使用您的查询和数据：

SELECT * FROM items WHERE itemStatus = '1' AND itemAdded > '$timestamp'
SELECT * FROM locations WHERE locationID = '$locationID'
SELECT * FROM categories WHERE categoryID = '$categoryID'

$locationName = $this->getLocationByName($locationID);
$categoryParentName = $this->getCategoryByName($categoryParentID);
$categoryName = $this->getCategoryByName($categoryID);

如果这返回了预期的结果集，请告诉我。 希望这可以帮助

SELECT 
    it.itemID, it.itemLocationID, it.categoryParentID, it.categoryID, it.itemName, it.itemDetails,
    l.locationID, l.locationName, l.locationLink, 
    c.categoryID, c.categoryName, c.categoryLink
FROM items it 
LEFT JOIN locations l ON l.locationID = it.itemLocationID 
LEFT JOIN categories c ON c.categoryID = it.categoryID 
WHERE 
    it.itemStatus = '1' 
    AND it.itemAdded > '$timestamp'

使用categoryParentID更新查询 - 我不是说效率很高，但您可以根据需要进行测试和优化。

一种选择是更新上面的查询 - 不确定是否有效 - 对于使用OR的大型结果集效率不高：

LEFT JOIN categories c ON (c.categoryID = it.categoryID OR c.categoryID = it.categoryParentID)

我看到的另一个选项是获得2个结果集（见下文） - 一个用于categId = categId，第二个用于categId = categParentId，并将结果集合并在一个大结果集中。

SELECT 
    t.itemID, t.itemLocationID, t.categoryParentID, t.categoryID, t.itemName, t.itemDetails,
    l.locationID, l.locationName, l.locationLink, 
    t.categoryID, t.categoryName, t.categoryLink 
FROM 
(
SELECT 
    it.itemID, it.itemLocationID, it.categoryParentID, it.categoryID, it.itemName, it.itemDetails,
    c.categoryID, c.categoryName, c.categoryLink
FROM items it 
INNER JOIN categories c ON c.categoryID = it.categoryID 
WHERE 
    it.itemStatus = '1' 
    AND it.itemAdded > '$timestamp'

UNION -- [ALL]

SELECT 
    it.itemID, it.itemLocationID, it.categoryParentID, it.categoryID, it.itemName, it.itemDetails,
    c.categoryID, c.categoryName, c.categoryLink
FROM items it 
INNER JOIN categories c ON c.categoryID = it.categoryParentID 
WHERE 
    it.itemStatus = '1' AND 
    it.itemAdded > '$timestamp'
) AS t 
LEFT JOIN locations l ON l.locationID = t.itemLocationID 

其他想法 - 未测试并假设id为int - 将必须转换为字符串/ char。 如何编写此查询有几个选项 - 如果您发布结构表和一些虚拟数据，我相信有人会创建一个demo / sqlfiddle。

SELECT 
    it.itemID, it.itemLocationID, it.categoryParentID, it.categoryID, it.itemName, it.itemDetails,
    l.locationID, l.locationName, l.locationLink, 
    c.categoryID, c.categoryName, c.categoryLink
FROM items it 
LEFT JOIN locations l ON l.locationID = it.itemLocationID 
WHERE 
    it.itemStatus = '1' 
    AND it.itemAdded > '$timestamp' 
    AND c.category ID IN ( SELECT GROUP_CONCAT(categs) FROM (SELECT CONCAT(categoryID, ",", categoryParentID) AS categs FROM items ))

Answer 2

我不会在select语句中使用*带有连接的查询可能是

SELECT 
    i.itemID, 
    i.itemLocationID,
    i.categoryParentID,
    i.categoryID, 
    i.itemName,
    i.itemDetails,
    l.*,
    c.*        
FROM 
    items i
    inner join locations l on i.itemLocationID = l.locationID
    inner join categories c on i.categoryID = c.categoryID
WHERE
    itemStatus = '1'
    AND itemAdded > '$timestamp'

我希望它对你有用。 干杯!

Answer 3

除非我遗漏了一些明显的东西，否则我可能会建议这样的事情作为第一个开始：

select *
  from items i
  join locations l 
    on i.location_id=l.location_id
  join categories c
    on i.category_id=c.category_id
 where item_status='1'
   and itemAdded > '$timestamp'