[英]Multiple Insert and Select Statements From Multiple Tables into one Query?
我将这些都作为 Cron 作业 PHP 运行并且它正在运行,但似乎运行缓慢,而且我认为它的效率不高。 有 5 个查询,其背后的基本思想是在表中查找新的 SKU 并将它们插入到 MasterSKU 表中。
INSERT INTO MasterSKU (SKU)
SELECT DISTINCT SKU
FROM AmazonListings
WHERE NOT EXISTS (SELECT SKU
FROM MasterSKU
WHERE AmazonListings.SKU = MasterSKU.SKU);
INSERT INTO MasterSKU (SKU)
SELECT DISTINCT SKU
FROM ShopifyListings
WHERE NOT EXISTS (SELECT SKU
FROM MasterSKU
WHERE ShopifyListings.SKU = MasterSKU.SKU);
INSERT INTO MasterSKU (SKU)
SELECT DISTINCT SKU
FROM eBayListings_1
WHERE NOT EXISTS (SELECT SKU
FROM MasterSKU
WHERE eBayListings_1.SKU = MasterSKU.SKU);
INSERT INTO MasterSKU (SKU)
SELECT DISTINCT SKU
FROM eBayListings_2
WHERE NOT EXISTS (SELECT SKU
FROM MasterSKU
WHERE eBayListings_2.SKU = MasterSKU.SKU);
INSERT INTO MasterSKU (SKU)
SELECT DISTINCT SKU
FROM eBayListings_3
WHERE NOT EXISTS (SELECT SKU
FROM MasterSKU
WHERE eBayListings_3.SKU = MasterSKU.SKU);
然后我将一一进入 PHP 脚本并使用mysqli_query
来执行每个单独的查询。
是否有可能将所有的这些,即使他们都来FROM
不同的表? 或者有没有更好、更优化的方法来做到这一点?
答案是否定的。
不是,因为如果要从多个互不相关的表中提取数据,则需要使用单独的查询。
是的,因为在 sql 中,您可以使用union将多个查询的结果附加在一起 - 前提是它们具有相同数量的字段。
INSERT INTO MasterSKU (SKU)
(SELECT DISTINCT SKU
FROM AmazonListings
WHERE NOT EXISTS (SELECT SKU
FROM MasterSKU
WHERE AmazonListings.SKU = MasterSKU.SKU))
union
(SELECT DISTINCT SKU
FROM ShopifyListings
WHERE NOT EXISTS (SELECT SKU
FROM MasterSKU
WHERE ShopifyListings.SKU = MasterSKU.SKU)
union ...
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