內部聯接性能降低

Question

我有一個表提供的行超過10萬行，因此下面的查詢非常慢（4秒-平均）。

SELECT cat1.id AS cat1id, 
    cat1.title_gr AS title, 
    cat1.order

    FROM categories_groups_cat1 AS cat1

    INNER JOIN 
      ( SELECT categories_id, categories_groups_cat1_id FROM
        categories_vs_groups
        GROUP BY categories_groups_cat1_id ) AS vs
    ON vs.categories_groups_cat1_id=cat1.id

    INNER JOIN 
      ( SELECT id, title_gr FROM
        categories
        GROUP BY title_gr ) AS cats
    ON cats.id=vs.categories_id

   INNER JOIN 
      ( SELECT category_gr FROM
        offers
        GROUP BY category_gr ) AS offers
    ON offers.category_gr=cats.title_gr

    GROUP BY cat1.id
    ORDER BY cat1.order ASC 

餐桌優惠

`id` int(11) NOT NULL,
`title` text NOT NULL,
`description` text NOT NULL,
`image` text NOT NULL,
`price` float NOT NULL,
`start_price` float NOT NULL,
`brand` text NOT NULL
`category_gr` text NOT NULL

表category_groups_cat1

`id` int(11) NOT NULL,
`order` int(11) NOT NULL,
`title_gr` text NOT NULL

表category_vs_groups

`id` int(11) NOT NULL,
`categories_groups_cat1_id` int(11) NOT NULL,
`categories_id` int(11) NOT NULL

表類別

`id` int(11) NOT NULL,
`title_gr` char(255) NOT NULL

我嘗試從提供報價的category_groups_cat1中進行選擇，這就是為什么使用內部聯接的原因。 我不知道這是否完全正確。 如果有另一個更快的（性能）解決方案，我將不勝感激

Answer 1

您應該避免創建臨時表的子查詢。 這肯定會提高性能。 在內存中創建臨時表的子查詢會降低性能，請盡量避免使用。

我已經修改了您的代碼。 可能有小的語法錯誤。

  SELECT cat1.id AS cat1id, 
        cat1.title_gr AS title, 
        cat1.order

        FROM categories_groups_cat1 AS cat1

        INNER JOIN 
          categories_groups_cat1_id  AS vs
        ON vs.categories_groups_cat1_id=cat1.id

        INNER JOIN 

            categories
             AS cats
        ON cats.id=vs.categories_id

       INNER JOIN 

            offers

        ON offers.category_gr=cats.title_gr

        GROUP BY cat1.id,cats.title_gr, offers.category_gr
        ORDER BY cat1.order ASC