{"id":3685,"date":"2025-05-10T17:19:37","date_gmt":"2025-05-10T09:19:37","guid":{"rendered":"https:\/\/www.laixuexila.com\/?p=3685"},"modified":"2025-05-10T17:19:37","modified_gmt":"2025-05-10T09:19:37","slug":"%e8%a6%86%e7%9b%96%e7%b4%a2%e5%bc%95%e6%98%af%e4%bb%80%e4%b9%88%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/www.laixuexila.com\/index.php\/2025\/05\/10\/%e8%a6%86%e7%9b%96%e7%b4%a2%e5%bc%95%e6%98%af%e4%bb%80%e4%b9%88%ef%bc%9f\/","title":{"rendered":"\u8986\u76d6\u7d22\u5f15\u662f\u4ec0\u4e48\uff1f"},"content":{"rendered":"\n

\u8986\u76d6\u7d22\u5f15\uff08Covering Index\uff09<\/strong> \u662f\u4e00\u79cd\u80fd\u591f\u5b8c\u5168\u6ee1\u8db3\u67e5\u8be2\u8bf7\u6c42\u800c\u65e0\u9700\u8bbf\u95ee\u8868\u6570\u636e\u7684\u7d22\u5f15\u3002\u5177\u4f53\u6765\u8bf4\uff0c\u5f53\u4e00\u4e2a\u7d22\u5f15\u5305\u542b\u4e86\u67e5\u8be2\u8bed\u53e5\u6240\u9700\u8981\u7684\u6240\u6709\u5217\uff08\u5305\u62ec SELECT<\/code>\u3001WHERE<\/code>\u3001ORDER BY<\/code> \u548c GROUP BY<\/code> \u7b49\u6d89\u53ca\u7684\u5217\uff09\u65f6\uff0c\u5c31\u79f0\u4e3a\u8986\u76d6\u7d22\u5f15\u3002<\/p>\n\n\n\n

1. \u8986\u76d6\u7d22\u5f15\u7684\u7279\u70b9<\/strong><\/h3>\n\n\n\n
    \n
  • \u51cf\u5c11 I\/O<\/strong>\uff1a\u53ea\u9700\u8bbf\u95ee\u7d22\u5f15\u9875\uff0c\u51cf\u5c11\u78c1\u76d8 I\/O \u5f00\u9500\u3002<\/li>\n\n\n\n
  • \u63d0\u9ad8\u67e5\u8be2\u6548\u7387<\/strong>\uff1a\u907f\u514d\u56de\u8868\u67e5\u8be2\uff0c\u901f\u5ea6\u66f4\u5feb\u3002<\/li>\n\n\n\n
  • \u51cf\u5c11\u9501\u4e89\u7528<\/strong>\uff1a\u4ec5\u8bbf\u95ee\u7d22\u5f15\uff0c\u51cf\u5c11\u5bf9\u6570\u636e\u9875\u7684\u9501\u7ade\u4e89\u3002<\/li>\n<\/ul>\n\n\n\n

    2. \u8986\u76d6\u7d22\u5f15\u7684\u793a\u4f8b<\/strong><\/h3>\n\n\n\n

    \u5047\u8bbe\u6709\u5982\u4e0b users<\/code> \u8868\uff1a<\/p>\n\n\n\n

    CREATE TABLE users (\n    id INT PRIMARY KEY,\n    username VARCHAR(50),\n    email VARCHAR(100),\n    age INT,\n    created_at DATETIME\n);<\/code><\/pre>\n\n\n\n
    \u521b\u5efa\u4e00\u4e2a\u590d\u5408\u7d22\u5f15\uff1a<\/p>\n\n\n\n
    CREATE INDEX idx_users_username_email ON users (username, email);<\/code><\/pre>\n\n\n\n
    \u6267\u884c\u4ee5\u4e0b\u67e5\u8be2\uff1a<\/p>\n\n\n\n
    SELECT username, email FROM users WHERE username = 'Alice';<\/code><\/pre>\n\n\n\n
    \u4f7f\u7528\u8986\u76d6\u7d22\u5f15\u7684\u539f\u56e0<\/strong>\uff1a<\/p>\n\n\n\n
      \n
    • \u7d22\u5f15 idx_users_username_email<\/code> \u5305\u542b\u4e86 username<\/code> \u548c email<\/code> \u5217\uff0c\u56e0\u6b64\u67e5\u8be2\u53ef\u4ee5\u5b8c\u5168\u901a\u8fc7\u7d22\u5f15\u89e3\u51b3\uff0c\u65e0\u9700\u8bbf\u95ee users<\/code> \u8868\u7684\u6570\u636e\u9875\u3002<\/li>\n<\/ul>\n\n\n\n
      3. \u8986\u76d6\u7d22\u5f15\u7684\u9650\u5236<\/strong><\/h3>\n\n\n\n
        \n
      • \u5b57\u6bb5\u9650\u5236<\/strong>\uff1a\u8986\u76d6\u7d22\u5f15\u53ea\u80fd\u8986\u76d6\u90a3\u4e9b\u5728\u7d22\u5f15\u4e2d\u660e\u786e\u5b58\u5728\u7684\u5217\u3002<\/li>\n\n\n\n
      • \u7a7a\u95f4\u6d88\u8017<\/strong>\uff1a\u8986\u76d6\u7d22\u5f15\u5f80\u5f80\u5305\u542b\u66f4\u591a\u5217\uff0c\u5360\u7528\u66f4\u591a\u5b58\u50a8\u7a7a\u95f4\u3002<\/li>\n\n\n\n
      • \u7ef4\u62a4\u6210\u672c<\/strong>\uff1a\u6d89\u53ca\u5217\u8f83\u591a\u65f6\uff0c\u66f4\u65b0\u548c\u63d2\u5165\u64cd\u4f5c\u7684\u4ee3\u4ef7\u66f4\u9ad8\u3002<\/li>\n<\/ul>\n\n\n\n
        4. \u4ec0\u4e48\u65f6\u5019\u4f7f\u7528\u8986\u76d6\u7d22\u5f15<\/strong><\/h3>\n\n\n\n
          \n
        • \u8bfb\u591a\u5199\u5c11\u7684\u573a\u666f\u3002<\/li>\n\n\n\n
        • \u9700\u8981\u9ad8\u6027\u80fd\u7684\u67e5\u8be2\u3002<\/li>\n\n\n\n
        • \u8868\u6570\u636e\u8f83\u5927\u4e14\u9891\u7e41\u8bbf\u95ee\u90e8\u5206\u5217\u3002<\/li>\n<\/ul>\n\n\n\n
          \n\n\n\n
          \u66f4\u591a\u8be6\u7ec6\u5185\u5bb9\u8bf7\u5173\u6ce8\u5176\u4ed6\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"
          \u8986\u76d6\u7d22\u5f15\uff08Covering Index\uff09 \u662f\u4e00\u79cd\u80fd\u591f\u5b8c\u5168\u6ee1\u8db3\u67e5\u8be2\u8bf7\u6c42\u800c\u65e0\u9700\u8bbf\u95ee\u8868\u6570\u636e\u7684\u7d22\u5f15\u3002\u5177\u4f53\u6765\u8bf4\uff0c\u5f53\u4e00\u4e2a\u7d22 […]<\/p>\n","protected":false},"author":1,"featured_media":3686,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[87],"tags":[],"class_list":["post-3685","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-mysql"],"_links":{"self":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/3685","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/comments?post=3685"}],"version-history":[{"count":1,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/3685\/revisions"}],"predecessor-version":[{"id":3687,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/3685\/revisions\/3687"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media\/3686"}],"wp:attachment":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media?parent=3685"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/categories?post=3685"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/tags?post=3685"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}