{"id":443,"date":"2024-12-22T13:04:09","date_gmt":"2024-12-22T05:04:09","guid":{"rendered":"https:\/\/www.laixuexila.com\/?p=443"},"modified":"2024-12-22T13:04:09","modified_gmt":"2024-12-22T05:04:09","slug":"%e5%9f%ba%e4%ba%8e%e4%b8%bb%e6%b5%81-sql-%e6%95%b0%e6%8d%ae%e5%ba%93%e7%9a%84%e5%a4%9a%e8%a1%a8%e6%9f%a5%e8%af%a2%e6%96%b9%e6%b3%95%e9%83%bd%e6%9c%89%e5%93%aa%e4%ba%9b%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/www.laixuexila.com\/index.php\/2024\/12\/22\/%e5%9f%ba%e4%ba%8e%e4%b8%bb%e6%b5%81-sql-%e6%95%b0%e6%8d%ae%e5%ba%93%e7%9a%84%e5%a4%9a%e8%a1%a8%e6%9f%a5%e8%af%a2%e6%96%b9%e6%b3%95%e9%83%bd%e6%9c%89%e5%93%aa%e4%ba%9b%ef%bc%9f\/","title":{"rendered":"\u57fa\u4e8e\u4e3b\u6d41 SQL \u6570\u636e\u5e93\u7684\u591a\u8868\u67e5\u8be2\u65b9\u6cd5\u90fd\u6709\u54ea\u4e9b\uff1f"},"content":{"rendered":"\n
\n

SQL \u7684\u591a\u8868\u67e5\u8be2\u968f\u7740\u6570\u636e\u5e93\u6280\u672f\u7684\u53d1\u5c55\uff0c\u7ed3\u5408\u5982\u7a97\u53e3\u51fd\u6570\u3001CTE\u3001JSON \u652f\u6301\u7b49\uff0c\u66f4\u9ad8\u6548\u4e14\u529f\u80fd\u66f4\u5f3a\u5927\u3002\u4ee5\u4e0b\u662f\u57fa\u4e8e\u4e3b\u6d41 SQL \u6570\u636e\u5e93\uff08\u5982 MySQL 8.0+\u3001PostgreSQL\u3001SQL Server \u7b49\uff09\u7684\u591a\u8868\u67e5\u8be2\u7684\u8be6\u7ec6\u8bb2\u89e3\u3002<\/p>\n<\/blockquote>\n\n\n\n

\n\n\n\n

1. \u591a\u8868\u67e5\u8be2\u7684\u57fa\u7840\u6982\u5ff5<\/strong><\/h2>\n\n\n\n

1.1 \u6570\u636e\u5e93\u7ed3\u6784<\/strong><\/h3>\n\n\n\n

\u5047\u8bbe\u6709\u4ee5\u4e0b\u4e24\u5f20\u8868\uff1a<\/p>\n\n\n\n

    \n
  • users \u8868<\/strong>\uff08\u7528\u6237\u4fe1\u606f\uff09<\/li>\n<\/ul>\n\n\n\n
      user_id | name      | email\n  ----------------------------\n  1       | Alice     | alice@example.com\n  2       | Bob       | bob@example.com\n  3       | Charlie   | charlie@example.com<\/code><\/pre>\n\n\n\n
      \n
    • orders \u8868<\/strong>\uff08\u8ba2\u5355\u4fe1\u606f\uff09<\/li>\n<\/ul>\n\n\n\n
        order_id | user_id | product_name   | price\n  --------------------------------------------\n  101      | 1       | Laptop         | 1000\n  102      | 1       | Smartphone     | 500\n  103      | 2       | Headphones     | 100<\/code><\/pre>\n\n\n\n
      \n\n\n\n
      2. \u5e38\u7528\u7684\u591a\u8868\u67e5\u8be2\u65b9\u6cd5<\/strong><\/h2>\n\n\n\n
      2.1. INNER JOIN\uff08\u5185\u8fde\u63a5\uff09<\/strong><\/h3>\n\n\n\n
      \u4ec5\u8fd4\u56de\u4e24\u5f20\u8868\u4e2d\u6709\u5339\u914d\u5173\u7cfb\u7684\u8bb0\u5f55\u3002<\/p>\n\n\n\n
      SELECT \n    users.name,\n    orders.product_name,\n    orders.price\nFROM \n    users\nINNER JOIN \n    orders\nON \n    users.user_id = orders.user_id;<\/code><\/pre>\n\n\n\n
      \u7ed3\u679c\uff1a<\/strong><\/p>\n\n\n\n
      name      | product_name   | price\n-----------------------------------\nAlice     | Laptop         | 1000\nAlice     | Smartphone     | 500\nBob       | Headphones     | 100<\/code><\/pre>\n\n\n\n
      2.2. LEFT JOIN\uff08\u5de6\u8fde\u63a5\uff09<\/strong><\/h3>\n\n\n\n
      \u8fd4\u56de\u5de6\u8868\u7684\u6240\u6709\u8bb0\u5f55\uff0c\u4ee5\u53ca\u53f3\u8868\u4e2d\u5339\u914d\u7684\u8bb0\u5f55\u3002\u5982\u679c\u6ca1\u6709\u5339\u914d\uff0c\u53f3\u8868\u5b57\u6bb5\u4e3a NULL<\/code>\u3002<\/p>\n\n\n\n
      SELECT \n    users.name,\n    orders.product_name,\n    orders.price\nFROM \n    users\nLEFT JOIN \n    orders\nON \n    users.user_id = orders.user_id;<\/code><\/pre>\n\n\n\n
      \u7ed3\u679c\uff1a<\/strong><\/p>\n\n\n\n
      name      | product_name   | price\n-----------------------------------\nAlice     | Laptop         | 1000\nAlice     | Smartphone     | 500\nBob       | Headphones     | 100\nCharlie   | NULL           | NULL<\/code><\/pre>\n\n\n\n
      \n\n\n\n
      2.3. RIGHT JOIN\uff08\u53f3\u8fde\u63a5\uff09<\/strong><\/h3>\n\n\n\n
      \u8fd4\u56de\u53f3\u8868\u7684\u6240\u6709\u8bb0\u5f55\uff0c\u4ee5\u53ca\u5de6\u8868\u4e2d\u5339\u914d\u7684\u8bb0\u5f55\u3002\u5982\u679c\u6ca1\u6709\u5339\u914d\uff0c\u5de6\u8868\u5b57\u6bb5\u4e3a NULL<\/code>\u3002<\/p>\n\n\n\n
      SELECT \n    users.name,\n    orders.product_name,\n    orders.price\nFROM \n    users\nRIGHT JOIN \n    orders\nON \n    users.user_id = orders.user_id;<\/code><\/pre>\n\n\n\n
      \u7ed3\u679c\uff1a<\/strong><\/p>\n\n\n\n
      name      | product_name   | price\n-----------------------------------\nAlice     | Laptop         | 1000\nAlice     | Smartphone     | 500\nBob       | Headphones     | 100<\/code><\/pre>\n\n\n\n
      \n\n\n\n
      2.4. FULL OUTER JOIN\uff08\u5168\u8fde\u63a5\uff09<\/strong><\/h3>\n\n\n\n
      \u8fd4\u56de\u5de6\u53f3\u8868\u7684\u6240\u6709\u8bb0\u5f55\uff0c\u65e0\u8bba\u662f\u5426\u5339\u914d\u3002\u5982\u679c\u67d0\u8868\u65e0\u5339\u914d\u9879\uff0c\u5bf9\u5e94\u5b57\u6bb5\u4e3a NULL<\/code>\u3002
      \u6ce8\u610f\uff1a<\/strong> MySQL \u4e0d\u76f4\u63a5\u652f\u6301 FULL JOIN\uff0c\u53ef\u901a\u8fc7 UNION<\/code> \u5b9e\u73b0\u3002<\/p>\n\n\n\n
      SELECT \n    users.name,\n    orders.product_name,\n    orders.price\nFROM \n    users\nLEFT JOIN \n    orders\nON \n    users.user_id = orders.user_id\n\nUNION\n\nSELECT \n    users.name,\n    orders.product_name,\n    orders.price\nFROM \n    users\nRIGHT JOIN \n    orders\nON \n    users.user_id = orders.user_id;<\/code><\/pre>\n\n\n\n
      \n\n\n\n
      2.5. \u4f7f\u7528 CTE \u4f18\u5316\u67e5\u8be2<\/strong><\/h3>\n\n\n\n
      CTE\uff08Common Table Expression\uff09\u8ba9\u590d\u6742\u67e5\u8be2\u66f4\u5177\u53ef\u8bfb\u6027\u3002<\/p>\n\n\n\n
      \u793a\u4f8b\uff1a\u67e5\u8be2\u6bcf\u4f4d\u7528\u6237\u7684\u603b\u8ba2\u5355\u91d1\u989d<\/h4>\n\n\n\n
      WITH UserOrders AS (\n    SELECT \n        users.user_id,\n        users.name,\n        SUM(orders.price) AS total_spent\n    FROM \n        users\n    LEFT JOIN \n        orders\n    ON \n        users.user_id = orders.user_id\n    GROUP BY \n        users.user_id, users.name\n)\nSELECT \n    name, \n    total_spent\nFROM \n    UserOrders\nORDER BY \n    total_spent DESC;<\/code><\/pre>\n\n\n\n
      \u7ed3\u679c\uff1a<\/strong><\/p>\n\n\n\n
      name      | total_spent\n------------------------\nAlice     | 1500\nBob       | 100\nCharlie   | NULL<\/code><\/pre>\n\n\n\n
      \n\n\n\n
      2.6. \u4f7f\u7528\u7a97\u53e3\u51fd\u6570\u5904\u7406\u590d\u6742\u7edf\u8ba1<\/strong><\/h3>\n\n\n\n
      \u7a97\u53e3\u51fd\u6570\u8ba9\u6211\u4eec\u80fd\u5728\u591a\u8868\u67e5\u8be2\u4e2d\u52a8\u6001\u8ba1\u7b97\u6392\u540d\u3001\u603b\u8ba1\u7b49\u4fe1\u606f\u3002<\/p>\n\n\n\n
      \u793a\u4f8b\uff1a\u67e5\u8be2\u7528\u6237\u7684\u8ba2\u5355\u603b\u91d1\u989d\u53ca\u6392\u540d<\/h4>\n\n\n\n
      SELECT \n    users.name,\n    SUM(orders.price) AS total_spent,\n    RANK() OVER (ORDER BY SUM(orders.price) DESC) AS rank\nFROM \n    users\nLEFT JOIN \n    orders\nON \n    users.user_id = orders.user_id\nGROUP BY \n    users.user_id, users.name;<\/code><\/pre>\n\n\n\n
      \u7ed3\u679c\uff1a<\/strong><\/p>\n\n\n\n
      name      | total_spent | rank\n---------------------------------\nAlice     | 1500        | 1\nBob       | 100         | 2\nCharlie   | NULL        | 3<\/code><\/pre>\n\n\n\n
      \n\n\n\n
      2.7. \u591a\u8868\u5d4c\u5957\u67e5\u8be2\uff08\u5b50\u67e5\u8be2\uff09<\/strong><\/h3>\n\n\n\n
      \u793a\u4f8b\uff1a\u67e5\u8be2\u603b\u8ba2\u5355\u91d1\u989d\u8d85\u8fc7 $500 \u7684\u7528\u6237<\/h4>\n\n\n\n
      SELECT \n    name\nFROM \n    users\nWHERE \n    user_id IN (\n        SELECT \n            user_id\n        FROM \n            orders\n        GROUP BY \n            user_id\n        HAVING \n            SUM(price) > 500\n    );<\/code><\/pre>\n\n\n\n
      \u7ed3\u679c\uff1a<\/strong><\/p>\n\n\n\n
      name\n-----\nAlice<\/code><\/pre>\n\n\n\n
      \n\n\n\n
      2.8. JSON \u652f\u6301\u7684\u591a\u8868\u67e5\u8be2<\/strong><\/h3>\n\n\n\n
      MySQL 8.0+ \u548c PostgreSQL \u652f\u6301\u5c06 JSON \u6570\u636e\u7c7b\u578b\u4e0e\u591a\u8868\u67e5\u8be2\u7ed3\u5408\u3002<\/p>\n\n\n\n
      \u793a\u4f8b\uff1a\u4ee5 JSON \u683c\u5f0f\u8fd4\u56de\u7528\u6237\u53ca\u5176\u8ba2\u5355<\/h4>\n\n\n\n
      SELECT \n    users.name,\n    JSON_ARRAYAGG(\n        JSON_OBJECT('product_name', orders.product_name, 'price', orders.price)\n    ) AS order_details\nFROM \n    users\nLEFT JOIN \n    orders\nON \n    users.user_id = orders.user_id\nGROUP BY \n    users.name;<\/code><\/pre>\n\n\n\n
      \u7ed3\u679c\uff1a<\/strong><\/p>\n\n\n\n
      name      | order_details\n--------------------------------------------\nAlice     | [{\"product_name\": \"Laptop\", \"price\": 1000}, \n             {\"product_name\": \"Smartphone\", \"price\": 500}]\nBob       | [{\"product_name\": \"Headphones\", \"price\": 100}]\nCharlie   | NULL<\/code><\/pre>\n\n\n\n
      \n\n\n\n
      3. \u6700\u4f73\u5b9e\u8df5\u4e0e\u4f18\u5316<\/strong><\/h2>\n\n\n\n
        \n
      1. \u7d22\u5f15\u4f18\u5316\uff1a<\/strong><\/li>\n<\/ol>\n\n\n\n
          \n
        • \u4e3a\u5e38\u7528\u7684 JOIN \u5b57\u6bb5\uff08\u5982 user_id<\/code>\uff09\u521b\u5efa\u7d22\u5f15\uff0c\u52a0\u5feb\u67e5\u8be2\u901f\u5ea6\u3002<\/li>\n<\/ul>\n\n\n\n
             CREATE INDEX idx_user_id ON orders(user_id);<\/code><\/pre>\n\n\n\n
            \n
          1. \u5206\u6b65\u8c03\u8bd5\uff1a<\/strong><\/li>\n<\/ol>\n\n\n\n
              \n
            • \u590d\u6742\u591a\u8868\u67e5\u8be2\u65f6\uff0c\u9010\u6b65\u6784\u5efa SQL\uff0c\u786e\u4fdd\u6bcf\u4e00\u6b65\u7ed3\u679c\u6b63\u786e\u3002<\/li>\n<\/ul>\n\n\n\n
                \n
              1. \u6ce8\u610f NULL \u5904\u7406\uff1a<\/strong><\/li>\n<\/ol>\n\n\n\n
                  \n
                • \u4f7f\u7528 COALESCE<\/code> \u66ff\u6362 NULL<\/code>\uff1a<\/li>\n<\/ul>\n\n\n\n
                     SELECT \n       COALESCE(total_spent, 0) AS total_spent\n   FROM \n       UserOrders;<\/code><\/pre>\n\n\n\n
                    \n
                  1. \u9009\u62e9\u9002\u5f53\u7684\u5de5\u5177\uff1a<\/strong><\/li>\n<\/ol>\n\n\n\n
                      \n
                    • \u4f7f\u7528\u73b0\u4ee3 SQL \u5ba2\u6237\u7aef\uff08\u5982 DBeaver\u3001DataGrip\uff09\u8c03\u8bd5\u548c\u53ef\u89c6\u5316\u591a\u8868\u67e5\u8be2\u3002<\/li>\n<\/ul>\n\n\n\n
                      \u66f4\u591a\u8be6\u7ec6\u5185\u5bb9\u8bf7\u5173\u6ce8\u5176\u4ed6\u76f8\u5173\u6587\u7ae0\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
                      SQL \u7684\u591a\u8868\u67e5\u8be2\u968f\u7740\u6570\u636e\u5e93\u6280\u672f\u7684\u53d1\u5c55\uff0c\u7ed3\u5408\u5982\u7a97\u53e3\u51fd\u6570\u3001CTE\u3001JSON \u652f\u6301\u7b49\uff0c\u66f4\u9ad8\u6548\u4e14\u529f\u80fd\u66f4\u5f3a\u5927\u3002\u4ee5\u4e0b\u662f\u57fa […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[36],"tags":[],"class_list":["post-443","post","type-post","status-publish","format-standard","hentry","category-sql"],"_links":{"self":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/443","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=443"}],"version-history":[{"count":1,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/443\/revisions"}],"predecessor-version":[{"id":444,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/443\/revisions\/444"}],"wp:attachment":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media?parent=443"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/categories?post=443"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/tags?post=443"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}