在MySQL Query中加入表而不是多個查詢

Question

我有這個問題

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

一旦這個查詢返回結果，我就會遍歷結果

結果數組是itemID，itemLocationID，categoryParentID，categoryID，itemName，itemDetails

在循環期間，我通過調用同一個類中的函數來運行其他三個查詢

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

函數getLocationByName執行此查詢;

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

這將返回locationID，locationName，locationLink的數組

函數getCategoryByName執行此查詢;

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

這將返回categoryID，categoryName，categoryLink的數組

有人可以幫我優化這個查詢，也許可以加入他們來保存這么多查詢。

提前致謝。

我現在正在使用此查詢

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

FROM項目i內部聯接位置l on i.locationID = l.locationID內部聯接類別c on i.categoryID = c.categoryID WHERE itemStatus ='1'AND itemAdded>'$ timestamp'“）或die（mysql_error（））;

結果是

Array

（[itemID] => 81300 [locationID] => 17 [categoryParentID] => 21 [categoryID] => 183 [itemName] => blah [itemDetails] => blah [locationName] =>很棒它按預期拉入位置。[locationLink] => blah [categoryName] =>輝煌它按預期拉入類別。[categoryLink] => blah）

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

Answer 1

我認為應該類似於下面的查詢。 我沒看到你在哪里使用$ categoryParentName。

使用您的查詢和數據：

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);

如果這返回了預期的結果集，請告訴我。 希望這可以幫助

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更新查詢 - 我不是說效率很高，但您可以根據需要進行測試和優化。

一種選擇是更新上面的查詢 - 不確定是否有效 - 對於使用OR的大型結果集效率不高：

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

我看到的另一個選項是獲得2個結果集（見下文） - 一個用於categId = categId，第二個用於categId = categParentId，並將結果集合並在一個大結果集中。

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 - 未測試並假設id為int - 將必須轉換為字符串/ char。 如何編寫此查詢有幾個選項 - 如果您發布結構表和一些虛擬數據，我相信有人會創建一個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

我不會在select語句中使用*帶有連接的查詢可能是

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'

我希望它對你有用。 干杯!

Answer 3

除非我遺漏了一些明顯的東西，否則我可能會建議這樣的事情作為第一個開始：

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'