{"id":447,"date":"2024-12-22T13:10:47","date_gmt":"2024-12-22T05:10:47","guid":{"rendered":"https:\/\/www.laixuexila.com\/?p=447"},"modified":"2024-12-22T13:10:47","modified_gmt":"2024-12-22T05:10:47","slug":"sql-%e7%9a%84%e7%ae%80%e5%8d%95%e6%9f%a5%e8%af%a2%e5%92%8c%e5%a4%8d%e6%9d%82%e6%9f%a5%e8%af%a2%e8%af%a6%e8%a7%a3","status":"publish","type":"post","link":"https:\/\/www.laixuexila.com\/index.php\/2024\/12\/22\/sql-%e7%9a%84%e7%ae%80%e5%8d%95%e6%9f%a5%e8%af%a2%e5%92%8c%e5%a4%8d%e6%9d%82%e6%9f%a5%e8%af%a2%e8%af%a6%e8%a7%a3\/","title":{"rendered":"SQL \u7684\u7b80\u5355\u67e5\u8be2\u548c\u590d\u6742\u67e5\u8be2\u8be6\u89e3"},"content":{"rendered":"\n
\n

SQL \u67e5\u8be2\u53ef\u4ee5\u5206\u4e3a\u7b80\u5355\u67e5\u8be2\u548c\u590d\u6742\u67e5\u8be2\uff0c\u7b80\u5355\u67e5\u8be2\u901a\u5e38\u7528\u4e8e\u83b7\u53d6\u57fa\u7840\u6570\u636e\uff0c\u800c\u590d\u6742\u67e5\u8be2\u5219\u6d89\u53ca\u591a\u8868\u8fde\u63a5\u3001\u5b50\u67e5\u8be2\u3001\u805a\u5408\u51fd\u6570\u7b49\u66f4\u4e3a\u9ad8\u7ea7\u7684\u529f\u80fd\u3002\u5728\u8fd9\u90e8\u5206\uff0c\u6211\u5c06\u8be6\u7ec6\u8bb2\u89e3 SQL \u7684\u7b80\u5355\u67e5\u8be2<\/strong> \u548c \u590d\u6742\u67e5\u8be2<\/strong>\uff0c\u5e76\u7ed3\u5408\u5b9e\u9645\u793a\u4f8b\u8fdb\u884c\u8bb2\u89e3\u3002<\/p>\n<\/blockquote>\n\n\n\n

\n\n\n\n

1. \u7b80\u5355\u67e5\u8be2<\/strong><\/h2>\n\n\n\n

\u7b80\u5355\u67e5\u8be2\u901a\u5e38\u53ea\u6d89\u53ca\u5355\u4e00\u8868\u683c\u7684\u6570\u636e\u68c0\u7d22\uff0c\u4e3b\u8981\u4f7f\u7528 SELECT<\/code> \u8bed\u53e5\u3002\u5b83\u662f\u6700\u5e38\u89c1\u7684\u67e5\u8be2\u65b9\u5f0f\uff0c\u9002\u7528\u4e8e\u57fa\u672c\u7684\u6570\u636e\u68c0\u7d22\u64cd\u4f5c\u3002<\/p>\n\n\n\n

1.1. \u67e5\u8be2\u6240\u6709\u6570\u636e<\/strong><\/h3>\n\n\n\n

\u901a\u8fc7 SELECT *<\/code> \u53ef\u4ee5\u9009\u62e9\u8868\u4e2d\u7684\u6240\u6709\u5217\u3002<\/p>\n\n\n\n

SELECT * FROM users;<\/code><\/pre>\n\n\n\n
\u89e3\u91ca\uff1a<\/strong><\/p>\n\n\n\n
    \n
  • SELECT *<\/code>\uff1a\u9009\u53d6\u6240\u6709\u5217\u3002<\/li>\n\n\n\n
  • FROM users<\/code>\uff1a\u6307\u5b9a\u8981\u67e5\u8be2\u7684\u8868 users<\/code>\u3002<\/li>\n<\/ul>\n\n\n\n
    \u7ed3\u679c\uff1a<\/strong><\/p>\n\n\n\n
    user_id | name    | email\n------------------------\n1       | Alice   | alice@example.com\n2       | Bob     | bob@example.com\n3       | Charlie | charlie@example.com<\/code><\/pre>\n\n\n\n
    1.2. \u67e5\u8be2\u7279\u5b9a\u5217<\/strong><\/h3>\n\n\n\n
    \u5982\u679c\u53ea\u9700\u8981\u7279\u5b9a\u7684\u5217\uff0c\u53ef\u4ee5\u660e\u786e\u6307\u5b9a\u5217\u540d\u3002<\/p>\n\n\n\n
    SELECT name, email FROM users;<\/code><\/pre>\n\n\n\n
    \u7ed3\u679c\uff1a<\/strong><\/p>\n\n\n\n
    name    | email\n-----------------------------\nAlice   | alice@example.com\nBob     | bob@example.com\nCharlie | charlie@example.com<\/code><\/pre>\n\n\n\n
    1.3. \u67e5\u8be2\u5e26\u6761\u4ef6\u7684\u6570\u636e\uff08WHERE \u5b50\u53e5\uff09<\/strong><\/h3>\n\n\n\n
    \u53ef\u4ee5\u901a\u8fc7 WHERE<\/code> \u8fc7\u6ee4\u6570\u636e\uff0c\u6761\u4ef6\u53ef\u4ee5\u4f7f\u7528\u903b\u8f91\u8fd0\u7b97\u7b26\u5982 =<\/code>, ><\/code>, <<\/code>, BETWEEN<\/code>, LIKE<\/code> \u7b49\u3002<\/p>\n\n\n\n
    SELECT * FROM users WHERE name = 'Alice';<\/code><\/pre>\n\n\n\n
    \u7ed3\u679c\uff1a<\/strong><\/p>\n\n\n\n
    user_id | name  | email\n--------------------------\n1       | Alice | alice@example.com<\/code><\/pre>\n\n\n\n
    \u793a\u4f8b\uff1a\u67e5\u8be2\u540d\u5b57\u5305\u542b ‘a’ \u7684\u7528\u6237<\/h4>\n\n\n\n
    SELECT * FROM users WHERE name LIKE '%a%';<\/code><\/pre>\n\n\n\n
    \u7ed3\u679c\uff1a<\/strong><\/p>\n\n\n\n
    user_id | name    | email\n--------------------------\n1       | Alice   | alice@example.com\n3       | Charlie | charlie@example.com<\/code><\/pre>\n\n\n\n
    1.4. \u6392\u5e8f\u67e5\u8be2\uff08ORDER BY\uff09<\/strong><\/h3>\n\n\n\n
    \u4f7f\u7528 ORDER BY<\/code> \u5bf9\u67e5\u8be2\u7ed3\u679c\u8fdb\u884c\u6392\u5e8f\uff0c\u652f\u6301\u5347\u5e8f\uff08ASC\uff09\u548c\u964d\u5e8f\uff08DESC\uff09\u3002<\/p>\n\n\n\n
    SELECT * FROM users ORDER BY name ASC;<\/code><\/pre>\n\n\n\n
    \u7ed3\u679c\uff1a<\/strong><\/p>\n\n\n\n
    user_id | name    | email\n------------------------\n1       | Alice   | alice@example.com\n2       | Bob     | bob@example.com\n3       | Charlie | charlie@example.com<\/code><\/pre>\n\n\n\n
    1.5. \u9650\u5236\u8fd4\u56de\u8bb0\u5f55\u6570\uff08LIMIT\uff09<\/strong><\/h3>\n\n\n\n
    \u4f7f\u7528 LIMIT<\/code> \u63a7\u5236\u67e5\u8be2\u8fd4\u56de\u7684\u6700\u5927\u884c\u6570\u3002<\/p>\n\n\n\n
    SELECT * FROM users LIMIT 2;<\/code><\/pre>\n\n\n\n
    \u7ed3\u679c\uff1a<\/strong><\/p>\n\n\n\n
    user_id | name    | email\n------------------------\n1       | Alice   | alice@example.com\n2       | Bob     | bob@example.com<\/code><\/pre>\n\n\n\n
    \n\n\n\n
    2. \u590d\u6742\u67e5\u8be2<\/strong><\/h2>\n\n\n\n
    \u590d\u6742\u67e5\u8be2\u6d89\u53ca\u591a\u4e2a\u8868\u8fde\u63a5\uff08JOIN\uff09\u3001\u5b50\u67e5\u8be2\u3001\u805a\u5408\u51fd\u6570\u3001\u7a97\u53e3\u51fd\u6570\u7b49\u529f\u80fd\uff0c\u901a\u5e38\u7528\u4e8e\u4ece\u591a\u4e2a\u89d2\u5ea6\u83b7\u53d6\u6570\u636e\u6216\u8fdb\u884c\u6df1\u5165\u5206\u6790\u3002<\/p>\n\n\n\n
    2.1. \u591a\u8868\u8fde\u63a5\uff08JOIN\uff09<\/strong><\/h3>\n\n\n\n
    \u591a\u8868\u67e5\u8be2\u5e38\u5e38\u901a\u8fc7 JOIN<\/code> \u5b9e\u73b0\uff0c\u5b83\u5141\u8bb8\u4f60\u4ece\u591a\u4e2a\u8868\u4e2d\u7ed3\u5408\u6570\u636e\u3002<\/p>\n\n\n\n
    2.1.1. \u5185\u8fde\u63a5\uff08INNER JOIN\uff09<\/strong><\/h4>\n\n\n\n
    \u8fd4\u56de\u4e24\u4e2a\u8868\u4e2d\u5339\u914d\u7684\u8bb0\u5f55\u3002<\/p>\n\n\n\n
    \u5047\u8bbe\u6709\u4ee5\u4e0b\u4e24\u5f20\u8868\uff1a<\/p>\n\n\n\n
    users \u8868\uff1a<\/strong><\/p>\n\n\n\n
    user_id | name\n----------------\n1       | Alice\n2       | Bob\n3       | Charlie<\/code><\/pre>\n\n\n\n
    orders \u8868\uff1a<\/strong><\/p>\n\n\n\n
    order_id | user_id | product\n--------------------------------\n101      | 1       | Laptop\n102      | 2       | Phone\n103      | 1       | Tablet<\/code><\/pre>\n\n\n\n
    \u5185\u8fde\u63a5\u67e5\u8be2\uff0c\u83b7\u53d6\u6bcf\u4e2a\u7528\u6237\u53ca\u5176\u8ba2\u5355\uff1a<\/p>\n\n\n\n
    SELECT users.name, orders.product\nFROM users\nINNER JOIN orders ON users.user_id = orders.user_id;<\/code><\/pre>\n\n\n\n
    \u7ed3\u679c\uff1a<\/strong><\/p>\n\n\n\n
    name    | product\n---------------------\nAlice   | Laptop\nAlice   | Tablet\nBob     | Phone<\/code><\/pre>\n\n\n\n
    2.1.2. \u5de6\u8fde\u63a5\uff08LEFT JOIN\uff09<\/strong><\/h4>\n\n\n\n
    \u8fd4\u56de\u5de6\u8868\uff08\u7b2c\u4e00\u4e2a\u8868\uff09\u7684\u6240\u6709\u8bb0\u5f55\uff0c\u5373\u4f7f\u53f3\u8868\u6ca1\u6709\u5339\u914d\u7684\u8bb0\u5f55\u3002<\/p>\n\n\n\n
    SELECT users.name, orders.product\nFROM users\nLEFT JOIN orders ON users.user_id = orders.user_id;<\/code><\/pre>\n\n\n\n
    \u7ed3\u679c\uff1a<\/strong><\/p>\n\n\n\n
    name    | product\n----------------------\nAlice   | Laptop\nAlice   | Tablet\nBob     | Phone\nCharlie | NULL<\/code><\/pre>\n\n\n\n
    2.2. \u805a\u5408\u67e5\u8be2<\/strong><\/h3>\n\n\n\n
    \u805a\u5408\u51fd\u6570\u7528\u4e8e\u8ba1\u7b97\u6570\u636e\u7684\u603b\u548c\u3001\u5e73\u5747\u503c\u3001\u6700\u5927\u503c\u7b49\u3002<\/p>\n\n\n\n
    2.2.1. \u4f7f\u7528 GROUP BY<\/code> \u8fdb\u884c\u5206\u7ec4<\/strong><\/h4>\n\n\n\n
    SELECT user_id, COUNT(*) AS order_count\nFROM orders\nGROUP BY user_id;<\/code><\/pre>\n\n\n\n
    \u7ed3\u679c\uff1a<\/strong><\/p>\n\n\n\n
    user_id | order_count\n---------------------\n1       | 2\n2       | 1<\/code><\/pre>\n\n\n\n
    2.2.2. \u4f7f\u7528 HAVING<\/code> \u8fdb\u884c\u8fc7\u6ee4<\/strong><\/h4>\n\n\n\n
    HAVING<\/code> \u7528\u4e8e\u8fc7\u6ee4\u805a\u5408\u540e\u7684\u7ed3\u679c\uff0c\u7c7b\u4f3c WHERE<\/code>\uff0c\u4f46 WHERE<\/code> \u4e0d\u80fd\u7528\u4e8e\u805a\u5408\u7ed3\u679c\u3002<\/p>\n\n\n\n
    \u67e5\u8be2\u8ba2\u5355\u6570\u5927\u4e8e 1 \u7684\u7528\u6237\uff1a<\/p>\n\n\n\n
    SELECT user_id, COUNT(*) AS order_count\nFROM orders\nGROUP BY user_id\nHAVING COUNT(*) > 1;<\/code><\/pre>\n\n\n\n
    \u7ed3\u679c\uff1a<\/strong><\/p>\n\n\n\n
    user_id | order_count\n---------------------\n1       | 2<\/code><\/pre>\n\n\n\n
    2.3. \u5b50\u67e5\u8be2<\/strong><\/h3>\n\n\n\n
    \u5b50\u67e5\u8be2\u662f\u5d4c\u5957\u5728\u5176\u4ed6\u67e5\u8be2\u4e2d\u7684\u67e5\u8be2\uff0c\u5e38\u7528\u4e8e\u66f4\u590d\u6742\u7684\u6761\u4ef6\u5224\u65ad\u3002<\/p>\n\n\n\n
    2.3.1. \u7b80\u5355\u5b50\u67e5\u8be2<\/strong><\/h4>\n\n\n\n
    \u67e5\u8be2\u4ef7\u683c\u5927\u4e8e\u67d0\u4e2a\u7528\u6237\u6240\u6709\u8ba2\u5355\u4ef7\u683c\u7684\u7528\u6237\uff1a<\/p>\n\n\n\n
    SELECT * FROM users\nWHERE user_id IN (\n    SELECT user_id FROM orders WHERE price > 500\n);<\/code><\/pre>\n\n\n\n
    2.3.2. \u5173\u8054\u5b50\u67e5\u8be2<\/strong><\/h4>\n\n\n\n
    \u67e5\u8be2\u8ba2\u5355\u4ef7\u683c\u8d85\u8fc7\u6240\u6709\u7528\u6237\u5e73\u5747\u4ef7\u683c\u7684\u7528\u6237\uff1a<\/p>\n\n\n\n
    SELECT name\nFROM users\nWHERE user_id IN (\n    SELECT user_id\n    FROM orders\n    WHERE price > (SELECT AVG(price) FROM orders)\n);<\/code><\/pre>\n\n\n\n
    2.4. \u7a97\u53e3\u51fd\u6570<\/strong><\/h3>\n\n\n\n
    \u7a97\u53e3\u51fd\u6570\u7528\u4e8e\u5728\u67e5\u8be2\u7ed3\u679c\u4e2d\u8fdb\u884c\u5206\u7ec4\u540e\u8ba1\u7b97\u6392\u540d\u3001\u603b\u8ba1\u7b49\uff0c\u80fd\u591f\u5728\u4fdd\u6301\u539f\u59cb\u6570\u636e\u7684\u57fa\u7840\u4e0a\uff0c\u8ba1\u7b97\u51fa\u989d\u5916\u7684\u4fe1\u606f\u3002<\/p>\n\n\n\n
    2.4.1. \u6392\u540d\u51fd\u6570\uff1aROW_NUMBER()<\/code>, RANK()<\/code>, DENSE_RANK()<\/code><\/strong><\/h4>\n\n\n\n
    \u4f8b\u5982\uff0c\u67e5\u8be2\u6bcf\u4e2a\u7528\u6237\u7684\u8ba2\u5355\u6392\u540d\uff1a<\/p>\n\n\n\n
    SELECT \n    user_id,\n    product,\n    RANK() OVER (PARTITION BY user_id ORDER BY order_date) AS order_rank\nFROM orders;<\/code><\/pre>\n\n\n\n
    2.4.2. \u805a\u5408\u7a97\u53e3\u51fd\u6570\uff1aSUM()<\/code>, AVG()<\/code><\/strong><\/h4>\n\n\n\n
    \u4f8b\u5982\uff0c\u8ba1\u7b97\u6bcf\u4e2a\u7528\u6237\u7684\u7d2f\u8ba1\u8ba2\u5355\u91d1\u989d\uff1a<\/p>\n\n\n\n
    SELECT \n    user_id,\n    product,\n    SUM(price) OVER (PARTITION BY user_id ORDER BY order_date) AS cumulative_sales\nFROM orders;<\/code><\/pre>\n\n\n\n
    2.5. \u8054\u5408\u67e5\u8be2\uff08UNION\uff09<\/strong><\/h3>\n\n\n\n
    UNION<\/code> \u7528\u4e8e\u5c06\u591a\u4e2a SELECT<\/code> \u67e5\u8be2\u7ed3\u679c\u5408\u5e76\uff0c\u8981\u6c42\u67e5\u8be2\u5217\u6570\u548c\u7c7b\u578b\u76f8\u540c\u3002<\/p>\n\n\n\n
    \u67e5\u8be2\u6240\u6709\u7528\u6237\u548c\u6240\u6709\u8ba2\u5355\u4fe1\u606f\uff1a<\/p>\n\n\n\n
    SELECT name AS info FROM users\nUNION\nSELECT product AS info FROM orders;<\/code><\/pre>\n\n\n\n
    \n\n\n\n
    3. \u67e5\u8be2\u4f18\u5316<\/strong><\/h2>\n\n\n\n
      \n
    1. \u4f7f\u7528\u7d22\u5f15\uff1a<\/strong><\/li>\n<\/ol>\n\n\n\n
        \n
      • \u5bf9\u5e38\u7528\u7684\u67e5\u8be2\u5b57\u6bb5\uff08\u5982 user_id<\/code>\u3001order_id<\/code>\uff09\u521b\u5efa\u7d22\u5f15\uff0c\u80fd\u591f\u52a0\u901f\u67e5\u8be2\u64cd\u4f5c\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. \u907f\u514d SELECT *<\/code>\uff1a<\/strong><\/li>\n<\/ol>\n\n\n\n
            \n
          • \u4ec5\u67e5\u8be2\u9700\u8981\u7684\u5b57\u6bb5\uff0c\u907f\u514d\u67e5\u8be2\u4e0d\u5fc5\u8981\u7684\u6570\u636e\u3002<\/li>\n<\/ul>\n\n\n\n
              \n
            1. \u9650\u5236\u8fd4\u56de\u7ed3\u679c\uff1a<\/strong><\/li>\n<\/ol>\n\n\n\n
                \n
              • \u4f7f\u7528 LIMIT<\/code> \u9650\u5236\u8fd4\u56de\u8bb0\u5f55\u6570\uff0c\u907f\u514d\u67e5\u8be2\u7ed3\u679c\u8fc7\u591a\u3002<\/li>\n<\/ul>\n\n\n\n
                  \n
                1. \u907f\u514d\u591a\u6b21\u5b50\u67e5\u8be2\uff1a<\/strong><\/li>\n<\/ol>\n\n\n\n
                    \n
                  • \u5c06\u91cd\u590d\u4f7f\u7528\u7684\u5b50\u67e5\u8be2\u63d0\u53d6\u4e3a CTE\uff08\u516c\u5171\u8868\u8868\u8fbe\u5f0f\uff09\uff0c\u63d0\u9ad8\u67e5\u8be2\u7684\u6548\u7387\u548c\u53ef\u8bfb\u6027\u3002<\/li>\n<\/ul>\n\n\n\n
                    \n\n\n\n
                    \u901a\u8fc7\u4e0a\u8ff0\u8bb2\u89e3\uff0c\u6211\u4eec\u53ef\u4ee5\u6e05\u695a\u5730\u770b\u5230 \u7b80\u5355\u67e5\u8be2<\/strong> \u548c \u590d\u6742\u67e5\u8be2<\/strong> \u5728 SQL \u4e2d\u7684\u4f7f\u7528\u548c\u533a\u522b\u3002\u7b80\u5355\u67e5\u8be2\u9002\u5408\u7b80\u5355\u7684\u6570\u636e\u68c0\u7d22\uff0c\u800c\u590d\u6742\u67e5\u8be2\u5219\u66f4\u5177\u7075\u6d3b\u6027\uff0c\u9002\u5408\u5904\u7406\u591a\u8868\u8fde\u63a5\u3001\u805a\u5408\u5206\u6790\u4ee5\u53ca\u66f4\u590d\u6742\u7684\u6570\u636e\u64cd\u4f5c\u3002\u66f4\u591a\u8be6\u7ec6\u5185\u5bb9\u8bf7\u5173\u6ce8\u5176\u4ed6\u76f8\u5173\u6587\u7ae0\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
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