[英]Avoid multiple SELECT in WHERE clause
我正在嘗試增強在商家網站中發現的SQL錯誤。
我有兩個表:
------ Table "products" ------
| id_product | product_name |
-----------------------------
| 1 | T-shirt |
| 2 | Trousers |
| 3 | Sweat-shirt |
| 4 | Socks |
----------- Table "features" -----------
| id_product | feature | feature_value |
----------------------------------------
| 1 | Color | Red |
| 1 | Size | M |
| 1 | Fabric | Cotton |
| 2 | Color | Blue |
| 2 | Size | S |
| 2 | Fabric | Polyester |
| 3 | Color | Red |
| 3 | Size | L |
| 3 | Fabric | Wool |
| 4 | Color | White |
| 4 | Size | L |
| 4 | Fabric | Cotton |
我正在嘗試檢索具有以下功能的產品:
我的查詢如下:
SELECT p.id_product
FROM products p
WHERE p.id_product IN (SELECT f.id_product FROM features f WHERE f.feature_value IN ("Red", "Blue"))
AND p.id_product IN (SELECT f.id_product FROM features f WHERE f.feature_value = "M")
AND p.id_product IN (SELECT f.id_product FROM features f WHERE f.feature_value = "Cotton")
GROUP BY p.id_product
(當然,實際上,我的表和查詢要比這復雜得多,我只關注有問題的部分)
如果選擇8個或更多功能,則WHERE子句中的多個SELECT會導致我的整個服務器速度變慢。 有沒有辦法避免在WHERE子句中進行這么多查詢?
編輯:例如,這是真正的查詢之一:
SELECT p.id_product id_product
FROM ps_product p
INNER JOIN ps_category_product cp ON p.id_product = cp.id_product
INNER JOIN ps_category c ON (c.id_category = cp.id_category AND c.nleft >= 6 AND c.nright <= 7 AND c.active = 1)
LEFT JOIN ps_stock_available sa ON (sa.id_product = p.id_product AND sa.id_shop = 1)
INNER JOIN ps_product_shop product_shop ON (product_shop.id_product = p.id_product AND product_shop.id_shop = 1)
WHERE 1
AND product_shop.active = 1
AND product_shop.visibility IN ("both", "catalog")
AND p.id_manufacturer IN (5,4)
AND sa.quantity > 0
AND p.id_product IN (SELECT id_product FROM ps_feature_product fp WHERE fp.id_feature_value = 82)
AND p.id_product IN (SELECT id_product FROM ps_feature_product fp WHERE fp.id_feature_value = 37248)
AND p.id_product IN (SELECT id_product FROM ps_feature_product fp WHERE fp.id_feature_value = 181)
AND p.id_product IN (SELECT id_product FROM ps_feature_product fp WHERE fp.id_feature_value = 37821)
AND p.id_product IN (SELECT id_product FROM ps_feature_product fp WHERE fp.id_feature_value = 33907)
AND p.id_product IN (SELECT id_product FROM ps_feature_product fp WHERE fp.id_feature_value = 33902)
AND p.id_product IN (SELECT id_product FROM ps_feature_product fp WHERE fp.id_feature_value = 70)
AND p.id_product IN (SELECT id_product FROM ps_feature_product fp WHERE fp.id_feature_value = 76)
AND p.id_product IN (SELECT id_product FROM ps_feature_product fp WHERE fp.id_feature_value = 291)
AND p.id_product IN (SELECT id_product FROM ps_feature_product fp WHERE fp.id_feature_value = 75)
AND p.id_product IN (SELECT id_product FROM ps_feature_product fp WHERE fp.id_feature_value = 44459)
GROUP BY id_product
您可以使用JOIN
和HAVING
子句:
SELECT p.id_product
FROM products p
JOIN features f
ON p.id_product = f.id_product
GROUP BY p.id_product
HAVING COUNT(CASE WHEN f.feature_value IN ('Red', 'Blue') THEN 1 END) > 0
AND COUNT(CASE WHEN f.feature_value = 'M' THEN 1 END) > 0
AND COUNT(CASE WHEN f.feature_value = 'Cotton' THEN 1 END) > 0;
甚至更短(MySQL):
HAVING SUM(f.feature_value IN ('Red', 'Blue')) > 0
AND SUM(f.feature_value = 'M') > 0
AND SUM(f.feature_value = 'Cotton') > 0;
SELECT
P.id_product
FROM
products P
INNER JOIN features F
ON P.id_product = F.id_product
WHERE
(F.featurure = 'Color' AND F.feature_value IN ('red', 'blue'))
OR (F.featurure = 'Size' AND F.feature_value IN ('M'))
OR (F.featurure = 'Fabric' AND F.feature_value IN ('Cotton'))
GROUP BY
P.id_product
HAVING
COUNT(DISTINCT F.feature) = 3
HAVING條件表明,至少應有3個不同的匹配功能(這是您的搜索字段的數量)。
試試這個,希望對您有所幫助。
SELECT p.id_product,count(f.feature_value)
FROM products p, features f
where f.id_product=p.id_product
and f.feature_value in ("Red","Blue")
or f.feature_value = "M"
or f.feature_value = "Cotton"
group by p.id_product
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