{"id":18319,"date":"2025-07-05T16:04:15","date_gmt":"2025-07-05T08:04:15","guid":{"rendered":"https:\/\/92it.top\/?p=18319"},"modified":"2025-07-05T16:04:15","modified_gmt":"2025-07-05T08:04:15","slug":"mysql%e6%9f%a5%e8%af%a2%e6%89%a7%e8%a1%8c%e9%a1%ba%e5%ba%8f%ef%bc%9a%e4%b8%80%e5%bc%a0%e5%9b%be%e7%9c%8b%e6%87%82sql%e6%98%af%e5%a6%82%e4%bd%95%e5%b7%a5%e4%bd%9c%e7%9a%84","status":"publish","type":"post","link":"https:\/\/92it.top\/?p=18319","title":{"rendered":"MySQL\u67e5\u8be2\u6267\u884c\u987a\u5e8f\uff1a\u4e00\u5f20\u56fe\u770b\u61c2SQL\u662f\u5982\u4f55\u5de5\u4f5c\u7684"},"content":{"rendered":"\n

\u8f6c\u8f7d\uff1aMySQL\u67e5\u8be2\u6267\u884c\u987a\u5e8f\uff1a\u4e00\u5f20\u56fe\u770b\u61c2SQL\u662f\u5982\u4f55\u5de5\u4f5c\u7684<\/a><\/p>\n\n\n\n

\ud83d\udd25 \u5f00\u7bc7\uff1a\u4e00\u4e2a\u8ba9\u4eba\u56f0\u60d1\u7684\u95ee\u9898<\/strong><\/p>\n\n\n\n

\n\n\n\n

\u4f60\u5199\u7684SQL\u8bed\u53e5\u4e3a\u4ec0\u4e48\u8fd9\u4e48\u6162\uff1f\u4e3a\u4ec0\u4e48\u6709\u65f6\u5019\u52a0\u4e86\u7d22\u5f15\u8fd8\u662f\u4e0d\u8d70\uff1f\u4e3a\u4ec0\u4e48GROUP BY\u8981\u653e\u5728WHERE\u540e\u9762\uff1f\u8fd9\u4e9b\u95ee\u9898\u7684\u7b54\u6848\u90fd\u85cf\u5728SQL\u7684\u6267\u884c\u987a\u5e8f\u91cc\uff01<\/p>\n\n\n\n

\u4f5c\u4e3a\u7a0b\u5e8f\u5458\uff0c\u4f60\u662f\u5426\u9047\u5230\u8fc7\u8fd9\u6837\u7684\u56f0\u60d1\uff1a<\/p>\n\n\n\n

-- \u8fd9\u4e2a\u67e5\u8be2\u4e3a\u4ec0\u4e48\u62a5\u9519\uff1f\nSELECT name, age, COUNT(*) as cnt\nFROM users \nWHERE age > 18 AND cnt > 5\nGROUP BY name;<\/pre>\n\n\n\n
\u660e\u660e\u903b\u8f91\u5f88\u6e05\u695a\uff1a\u67e5\u627e\u5e74\u9f84\u5927\u4e8e18\u5c81\uff0c\u4e14\u7edf\u8ba1\u6570\u91cf\u5927\u4e8e5\u7684\u7528\u6237\uff0c\u4e3a\u4ec0\u4e48MySQL\u5374\u544a\u8bc9\u4f60 cnt<\/code> \u5b57\u6bb5\u4e0d\u5b58\u5728\uff1f<\/p>\n\n\n\n
\u7b54\u6848\u5c31\u5728SQL\u7684\u6267\u884c\u987a\u5e8f\u91cc\uff01\u4eca\u5929\u6211\u4eec\u5c31\u6765\u63ed\u5f00\u8fd9\u4e2a\u795e\u79d8\u7684\u9762\u7eb1\u3002<\/p>\n\n\n\n
\u3000<\/p>\n\n\n\n
\ud83d\udccb SQL\u6267\u884c\u987a\u5e8f\u5168\u666f\u56fe<\/strong><\/p>\n\n\n\n
\n\n\n\n
\u8ba9\u6211\u4eec\u5148\u770b\u4e00\u4e2a\u5b8c\u6574\u7684SQL\u67e5\u8be2\u8bed\u53e5\uff1a<\/p>\n\n\n\n
SELECT DISTINCT column_name, COUNT(*)\nFROM table_name t1\nJOIN table_name2 t2 ON t1.id = t2.user_id\nWHERE condition\nGROUP BY column_name\nHAVING COUNT(*) > 1\nORDER BY column_name\nLIMIT 10 OFFSET 20;<\/pre>\n\n\n\n
\u4f60\u4ee5\u4e3aMySQL\u662f\u6309\u7167\u4f60\u5199\u7684\u987a\u5e8f\u6267\u884c\u7684\u5417\uff1f\u5927\u9519\u7279\u9519\uff01<\/strong><\/p>\n\n\n\n
MySQL\u7684\u771f\u5b9e\u6267\u884c\u987a\u5e8f\u662f\u8fd9\u6837\u7684\uff1a<\/p>\n\n\n
\n
\"\"<\/figure><\/div>\n\n\n
\u3000<\/p>\n\n\n\n
\ud83c\udfaf \u8be6\u89e3\u6bcf\u4e2a\u6267\u884c\u6b65\u9aa4<\/strong><\/p>\n\n\n\n
\n\n\n\n
    \n
  • \u7b2c1\u6b65\uff1aFROM – \u627e\u5230\u6570\u636e\u6e90<\/strong><\/li>\n<\/ul>\n\n\n\n
    FROM users u<\/pre>\n\n\n\n
    MySQL\u9996\u5148\u8981\u77e5\u9053\u6570\u636e\u4ece\u54ea\u91cc\u6765\uff0c\u6240\u4ee5\u7b2c\u4e00\u6b65\u662f\u786e\u5b9a\u8868\u548c\u7ed9\u8868\u8d77\u522b\u540d\u3002<\/p>\n\n\n\n
    \u8fd9\u4e00\u6b65\u505a\u4e86\u4ec0\u4e48\uff1f<\/strong><\/p>\n\n\n\n
      \n
    • \u2022 \u627e\u5230\u6307\u5b9a\u7684\u8868<\/li>\n\n\n\n
    • \u2022 \u4e3a\u8868\u521b\u5efa\u522b\u540d\uff08\u5982\u679c\u6709\u7684\u8bdd\uff09<\/li>\n\n\n\n
    • \u2022 \u51c6\u5907\u8bfb\u53d6\u6570\u636e<\/li>\n<\/ul>\n\n\n\n
      \u3000<\/p>\n\n\n\n
        \n
      • \u7b2c2\u6b65\uff1aJOIN – \u8fde\u63a5\u591a\u5f20\u8868<\/strong><\/li>\n<\/ul>\n\n\n\n
        FROM users u\nJOIN orders o ON u.id = o.user_id<\/pre>\n\n\n\n
        \u5982\u679c\u67e5\u8be2\u6d89\u53ca\u591a\u5f20\u8868\uff0cMySQL\u4f1a\u6839\u636eJOIN\u6761\u4ef6\u5c06\u5b83\u4eec\u8fde\u63a5\u8d77\u6765\u3002<\/p>\n\n\n\n
        \u5e38\u89c1\u7684JOIN\u7c7b\u578b\uff1a<\/strong><\/p>\n\n\n\n
          \n
        • \u2022\u00a0INNER JOIN<\/code>\uff1a\u53ea\u8fd4\u56de\u4e24\u8868\u90fd\u6709\u7684\u6570\u636e<\/li>\n\n\n\n
        • \u2022\u00a0LEFT JOIN<\/code>\uff1a\u8fd4\u56de\u5de6\u8868\u6240\u6709\u6570\u636e\uff0c\u53f3\u8868\u6ca1\u6709\u5219\u4e3aNULL<\/li>\n\n\n\n
        • \u2022\u00a0RIGHT JOIN<\/code>\uff1a\u8fd4\u56de\u53f3\u8868\u6240\u6709\u6570\u636e\uff0c\u5de6\u8868\u6ca1\u6709\u5219\u4e3aNULL<\/li>\n<\/ul>\n\n\n\n
          -- \u793a\u4f8b\uff1a\u67e5\u8be2\u7528\u6237\u53ca\u5176\u8ba2\u5355\u4fe1\u606f\nSELECT u.name, o.order_date\nFROM users u\nLEFT JOIN orders o ON u.id = o.user_id;<\/pre>\n\n\n\n
          \u3000<\/p>\n\n\n\n
            \n
          • \u7b2c3\u6b65\uff1aWHERE – \u8fc7\u6ee4\u4e0d\u9700\u8981\u7684\u884c<\/strong><\/li>\n<\/ul>\n\n\n\n
            WHERE u.age > 18 AND u.status = 'active'<\/pre>\n\n\n\n
            \u5728\u5206\u7ec4\u4e4b\u524d\uff0cMySQL\u4f1a\u6839\u636eWHERE\u6761\u4ef6\u8fc7\u6ee4\u6389\u4e0d\u7b26\u5408\u6761\u4ef6\u7684\u884c\u3002<\/p>\n\n\n\n
            \u6ce8\u610f\uff1aWHERE\u4e0d\u80fd\u4f7f\u7528\u805a\u5408\u51fd\u6570\uff01<\/strong><\/p>\n\n\n\n
            -- \u274c \u9519\u8bef\u5199\u6cd5\nSELECT name, COUNT(*) as cnt\nFROM users\nWHERE COUNT(*) > 5;  -- \u62a5\u9519\uff01\n\n-- \u2705 \u6b63\u786e\u5199\u6cd5\nSELECT name, COUNT(*) as cnt\nFROM users\nGROUP BY name\nHAVING COUNT(*) > 5;  -- \u7528HAVING<\/pre>\n\n\n\n
            \u3000<\/p>\n\n\n\n
              \n
            • \u7b2c4\u6b65\uff1aGROUP BY – \u6570\u636e\u5206\u7ec4<\/strong><\/li>\n<\/ul>\n\n\n\n
              GROUP BY u.department, u.position<\/pre>\n\n\n\n
              \u5c06\u6570\u636e\u6309\u7167\u6307\u5b9a\u7684\u5217\u8fdb\u884c\u5206\u7ec4\uff0c\u4e3a\u805a\u5408\u51fd\u6570\u505a\u51c6\u5907\u3002<\/p>\n\n\n\n
              \u5206\u7ec4\u793a\u4f8b\uff1a<\/strong><\/p>\n\n\n\n
              -- \u6309\u90e8\u95e8\u7edf\u8ba1\u5458\u5de5\u6570\u91cf\nSELECT department, COUNT(*) as employee_count\nFROM users\nWHERE status = 'active'\nGROUP BY department;<\/pre>\n\n\n\n
              \u3000<\/p>\n\n\n\n
                \n
              • \u7b2c5\u6b65\uff1aHAVING – \u8fc7\u6ee4\u5206\u7ec4<\/strong><\/li>\n<\/ul>\n\n\n\n
                HAVING COUNT(*) > 10<\/pre>\n\n\n\n
                HAVING\u662f\u5bf9\u5206\u7ec4\u540e\u7684\u7ed3\u679c\u8fdb\u884c\u8fc7\u6ee4\uff0c\u53ef\u4ee5\u4f7f\u7528\u805a\u5408\u51fd\u6570\u3002<\/p>\n\n\n\n
                WHERE vs HAVING \u5bf9\u6bd4\uff1a<\/strong><\/p>\n\n\n\n
                \u6761\u4ef6<\/td>WHERE<\/td>HAVING<\/td><\/tr><\/thead>
                \u6267\u884c\u65f6\u673a<\/td>\u5206\u7ec4\u524d<\/td>\u5206\u7ec4\u540e<\/td><\/tr>
                \u8fc7\u6ee4\u5bf9\u8c61<\/td>\u884c<\/td>\u5206\u7ec4<\/td><\/tr>
                \u80fd\u5426\u4f7f\u7528\u805a\u5408\u51fd\u6570<\/td>\u274c<\/td>\u2705<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
                \u3000<\/p>\n\n\n\n
                -- \u627e\u51fa\u8ba2\u5355\u6570\u91cf\u8d85\u8fc710\u7684\u7528\u6237\nSELECT user_id, COUNT(*) as order_count\nFROM orders\nWHERE order_status = 'completed'  -- \u5148\u8fc7\u6ee4\u5df2\u5b8c\u6210\u7684\u8ba2\u5355\nGROUP BY user_id\nHAVING COUNT(*) > 10;  -- \u518d\u8fc7\u6ee4\u8ba2\u5355\u6570\u91cf\u8d85\u8fc710\u7684\u7528\u6237<\/pre>\n\n\n\n
                \u3000<\/p>\n\n\n\n
                  \n
                • \u7b2c6\u6b65\uff1aSELECT – \u9009\u62e9\u8981\u663e\u793a\u7684\u5217<\/strong><\/li>\n<\/ul>\n\n\n\n
                  SELECT u.name, u.age, COUNT(o.id) as order_count<\/pre>\n\n\n\n
                  \u5230\u4e86\u8fd9\u4e00\u6b65\uff0cMySQL\u624d\u5f00\u59cb\u5904\u7406SELECT\u5b50\u53e5\uff0c\u9009\u62e9\u8981\u663e\u793a\u7684\u5217\u3002<\/p>\n\n\n\n
                  \u8fd9\u5c31\u662f\u4e3a\u4ec0\u4e48WHERE\u4e0d\u80fd\u4f7f\u7528SELECT\u4e2d\u5b9a\u4e49\u7684\u522b\u540d\uff01<\/strong><\/p>\n\n\n\n
                  -- \u274c \u9519\u8bef\uff1aWHERE\u6267\u884c\u5728SELECT\u4e4b\u524d\nSELECT name, age * 2 as double_age\nFROM users\nWHERE double_age > 50;  -- double_age\u8fd8\u4e0d\u5b58\u5728\uff01\n\n-- \u2705 \u6b63\u786e\u5199\u6cd5\nSELECT name, age * 2 as double_age\nFROM users\nWHERE age * 2 > 50;<\/pre>\n\n\n\n
                  \u3000\u3000<\/p>\n\n\n\n
                    \n
                  • \u7b2c7\u6b65\uff1aDISTINCT – \u53bb\u9664\u91cd\u590d<\/strong><\/li>\n<\/ul>\n\n\n\n
                    SELECT DISTINCT department\nFROM users;<\/pre>\n\n\n\n
                    \u5982\u679c\u4f7f\u7528\u4e86DISTINCT\uff0cMySQL\u4f1a\u53bb\u9664\u91cd\u590d\u7684\u884c\u3002<\/p>\n\n\n\n
                    \u3000<\/p>\n\n\n\n
                      \n
                    • \u7b2c8\u6b65\uff1aORDER BY – \u6392\u5e8f<\/strong><\/li>\n<\/ul>\n\n\n\n
                      ORDER BY u.age DESC, u.name ASC<\/pre>\n\n\n\n
                      \u5bf9\u6700\u7ec8\u7ed3\u679c\u8fdb\u884c\u6392\u5e8f\u3002<\/p>\n\n\n\n
                      ORDER BY\u53ef\u4ee5\u4f7f\u7528SELECT\u4e2d\u7684\u522b\u540d\uff1a<\/strong><\/p>\n\n\n\n
                      -- \u2705 \u6b63\u786e\uff1aORDER BY\u6267\u884c\u5728SELECT\u4e4b\u540e\nSELECT name, age * 2 as double_age\nFROM users\nORDER BY double_age DESC;  -- \u53ef\u4ee5\u4f7f\u7528\u522b\u540d<\/pre>\n\n\n\n
                      \u3000<\/p>\n\n\n\n
                        \n
                      • \u7b2c9\u6b65\uff1aLIMIT – \u9650\u5236\u7ed3\u679c\u6570\u91cf<\/strong><\/li>\n<\/ul>\n\n\n\n
                        LIMIT 10 OFFSET 20<\/pre>\n\n\n\n
                        \u6700\u540e\u4e00\u6b65\uff0c\u9650\u5236\u8fd4\u56de\u7684\u7ed3\u679c\u6570\u91cf\u3002<\/p>\n\n\n\n
                        \u3000<\/p>\n\n\n\n
                        \ud83d\udca1 \u5b9e\u6218\u6848\u4f8b\uff1a\u6267\u884c\u987a\u5e8f\u7684\u5e94\u7528<\/strong><\/p>\n\n\n\n
                        \n\n\n\n
                        \u8ba9\u6211\u4eec\u901a\u8fc7\u4e00\u4e2a\u5b9e\u9645\u6848\u4f8b\u6765\u7406\u89e3\u6267\u884c\u987a\u5e8f\uff1a<\/p>\n\n\n\n
                        -- \u9700\u6c42\uff1a\u67e5\u8be2\u6bcf\u4e2a\u90e8\u95e8\u4e2d\u5e74\u9f84\u5927\u4e8e25\u5c81\u7684\u5458\u5de5\u6570\u91cf\uff0c\n-- \u53ea\u663e\u793a\u5458\u5de5\u6570\u91cf\u8d85\u8fc75\u4eba\u7684\u90e8\u95e8\uff0c\u6309\u5458\u5de5\u6570\u91cf\u964d\u5e8f\u6392\u5217\n\nSELECT \n    department,\n    COUNT(*) as employee_count\nFROM users\nWHERE age > 25\nGROUP BY department  \nHAVING COUNT(*) > 5\nORDER BY employee_count DESC;<\/pre>\n\n\n\n
                        \u6267\u884c\u8fc7\u7a0b\u5206\u6790\uff1a<\/strong><\/p>\n\n\n\n
                          \n
                        1. 1.\u00a0FROM users<\/strong>\u00a0– \u786e\u5b9a\u6570\u636e\u6e90<\/li>\n\n\n\n
                        2. 2.\u00a0WHERE age > 25<\/strong>\u00a0– \u8fc7\u6ee4\u5e74\u9f84\u5927\u4e8e25\u7684\u5458\u5de5<\/li>\n\n\n\n
                        3. 3.\u00a0GROUP BY department<\/strong>\u00a0– \u6309\u90e8\u95e8\u5206\u7ec4<\/li>\n\n\n\n
                        4. 4.\u00a0HAVING COUNT(*) > 5<\/strong>\u00a0– \u8fc7\u6ee4\u5458\u5de5\u6570\u91cf\u8d85\u8fc75\u7684\u90e8\u95e8<\/li>\n\n\n\n
                        5. 5.\u00a0SELECT department, COUNT(*)<\/strong>\u00a0– \u9009\u62e9\u8981\u663e\u793a\u7684\u5217<\/li>\n\n\n\n
                        6. 6.\u00a0ORDER BY employee_count DESC<\/strong>\u00a0– \u6309\u5458\u5de5\u6570\u91cf\u964d\u5e8f\u6392\u5217<\/li>\n<\/ol>\n\n\n\n
                          \u3000<\/p>\n\n\n\n
                          \ud83d\ude80 \u6027\u80fd\u4f18\u5316\u6280\u5de7<\/strong><\/p>\n\n\n\n
                          \n\n\n\n
                          \u4e86\u89e3\u6267\u884c\u987a\u5e8f\u540e\uff0c\u6211\u4eec\u53ef\u4ee5\u8fdb\u884c\u4e00\u4e9b\u6027\u80fd\u4f18\u5316\uff1a<\/p>\n\n\n\n
                          1. WHERE\u6761\u4ef6\u4f18\u5316<\/p>\n\n\n\n
                          -- \u274c \u4f4e\u6548\uff1a\u5148JOIN\u518d\u8fc7\u6ee4\nSELECT u.name, o.order_date\nFROM users u\nJOIN orders o ON u.id = o.user_id\nWHERE u.status = 'active';\n\n-- \u2705 \u9ad8\u6548\uff1a\u5148\u8fc7\u6ee4\u518dJOIN\nSELECT u.name, o.order_date\nFROM (SELECT * FROM users WHERE status = 'active') u\nJOIN orders o ON u.id = o.user_id;<\/pre>\n\n\n\n
                          \u3000<\/p>\n\n\n\n
                          2. \u7d22\u5f15\u5229\u7528<\/p>\n\n\n\n
                          -- \u4e3aWHERE\u6761\u4ef6\u521b\u5efa\u7d22\u5f15\nCREATE INDEX idx_user_status_age ON users(status, age);\n\n-- \u67e5\u8be2\u4f1a\u81ea\u52a8\u4f7f\u7528\u7d22\u5f15\nSELECT * FROM users WHERE status = 'active' AND age > 25;<\/pre>\n\n\n\n
                          \u3000<\/p>\n\n\n\n
                          3. \u907f\u514d\u4e0d\u5fc5\u8981\u7684\u6392\u5e8f<\/p>\n\n\n\n
                          -- \u5982\u679c\u4e0d\u9700\u8981\u6392\u5e8f\uff0c\u4e0d\u8981\u4f7f\u7528ORDER BY\nSELECT department, COUNT(*)\nFROM users\nGROUP BY department;\n-- \u800c\u4e0d\u662f\nSELECT department, COUNT(*)\nFROM users\nGROUP BY department\nORDER BY department;  -- \u4e0d\u5fc5\u8981\u7684\u6392\u5e8f<\/pre>\n\n\n\n
                          \u3000<\/p>\n\n\n\n
                          \ud83d\udd27 \u5e38\u89c1\u9519\u8bef\u53ca\u89e3\u51b3\u65b9\u6848<\/strong><\/p>\n\n\n\n
                          \n\n\n\n
                          \u9519\u8bef1\uff1a\u5728WHERE\u4e2d\u4f7f\u7528\u805a\u5408\u51fd\u6570<\/p>\n\n\n\n
                          -- \u274c \u9519\u8bef\nSELECT department, COUNT(*) as cnt\nFROM users\nWHERE COUNT(*) > 5;\n\n-- \u2705 \u6b63\u786e\nSELECT department, COUNT(*) as cnt\nFROM users\nGROUP BY department\nHAVING COUNT(*) > 5;<\/pre>\n\n\n\n
                          \u3000<\/p>\n\n\n\n
                          \u9519\u8bef2\uff1a\u5728WHERE\u4e2d\u4f7f\u7528SELECT\u522b\u540d<\/p>\n\n\n\n
                          -- \u274c \u9519\u8bef\nSELECT name, salary * 12 as annual_salary\nFROM employees\nWHERE annual_salary > 100000;\n\n-- \u2705 \u6b63\u786e\nSELECT name, salary * 12 as annual_salary\nFROM employees\nWHERE salary * 12 > 100000;<\/pre>\n\n\n\n
                          \u3000<\/p>\n\n\n\n
                          \u9519\u8bef3\uff1aGROUP BY\u4e0eSELECT\u4e0d\u5339\u914d<\/p>\n\n\n\n
                          -- \u274c \u9519\u8bef\uff1aSELECT\u4e2d\u7684\u5217\u5fc5\u987b\u5728GROUP BY\u4e2d\uff0c\u6216\u8005\u662f\u805a\u5408\u51fd\u6570\nSELECT department, name, COUNT(*)\nFROM users\nGROUP BY department;\n\n-- \u2705 \u6b63\u786e\nSELECT department, COUNT(*)\nFROM users\nGROUP BY department;<\/pre>\n\n\n\n
                          \u3000\u3000<\/p>\n\n\n\n
                          \ud83d\udcca \u6267\u884c\u987a\u5e8f\u901f\u8bb0\u53e3\u8bc0<\/strong><\/p>\n\n\n\n
                          \n\n\n\n
                          \u4e3a\u4e86\u5e2e\u52a9\u5927\u5bb6\u8bb0\u5fc6\uff0c\u6211\u603b\u7ed3\u4e86\u4e00\u4e2a\u53e3\u8bc0\uff1a<\/p>\n\n\n\n
                          \"\u4ece\u54ea\u8fde\u4ec0\u4e48\uff0c\u5206\u7ec4\u518d\u7b5b\u9009\uff0c\u9009\u62e9\u53bb\u91cd\u6392\uff0c\u6700\u540e\u9650\u6570\u91cf\"<\/pre>\n\n\n\n
                            \n
                          • \u2022\u00a0\u4ece\u54ea<\/strong>\u00a0– FROM<\/li>\n\n\n\n
                          • \u2022\u00a0\u8fde\u4ec0\u4e48<\/strong>\u00a0– JOIN<\/li>\n\n\n\n
                          • \u2022\u00a0\u4ec0\u4e48<\/strong>\u00a0– WHERE<\/li>\n\n\n\n
                          • \u2022\u00a0\u5206\u7ec4<\/strong>\u00a0– GROUP BY<\/li>\n\n\n\n
                          • \u2022\u00a0\u518d\u7b5b\u9009<\/strong>\u00a0– HAVING<\/li>\n\n\n\n
                          • \u2022\u00a0\u9009\u62e9<\/strong>\u00a0– SELECT<\/li>\n\n\n\n
                          • \u2022\u00a0\u53bb\u91cd<\/strong>\u00a0– DISTINCT<\/li>\n\n\n\n
                          • \u2022\u00a0\u6392<\/strong>\u00a0– ORDER BY<\/li>\n\n\n\n
                          • \u2022\u00a0\u6700\u540e\u9650\u6570\u91cf<\/strong>\u00a0– LIMIT<\/li>\n<\/ul>\n\n\n\n
                            \u3000<\/p>\n\n\n\n
                            \ud83c\udfc6 \u5b9e\u6218\u7ec3\u4e60<\/strong><\/p>\n\n\n\n
                            \n\n\n\n
                            \u73b0\u5728\u8ba9\u6211\u4eec\u505a\u4e00\u4e2a\u5c0f\u7ec3\u4e60\uff0c\u770b\u770b\u4f60\u662f\u5426\u771f\u7684\u7406\u89e3\u4e86\u6267\u884c\u987a\u5e8f\uff1a<\/p>\n\n\n\n
                            -- \u9898\u76ee\uff1a\u4e0b\u9762\u8fd9\u4e2a\u67e5\u8be2\u7684\u6267\u884c\u987a\u5e8f\u662f\u4ec0\u4e48\uff1f\nSELECT \n    DISTINCT u.department,\n    AVG(u.salary) as avg_salary\nFROM users u\nJOIN departments d ON u.dept_id = d.id\nWHERE u.status = 'active' AND d.budget > 100000\nGROUP BY u.department\nHAVING AVG(u.salary) > 50000\nORDER BY avg_salary DESC\nLIMIT 5;<\/pre>\n\n\n\n
                            \u7b54\u6848\uff1a<\/strong><\/p>\n\n\n\n
                              \n
                            1. 1. FROM users u – \u786e\u5b9a\u4e3b\u8868<\/li>\n\n\n\n
                            2. 2. JOIN departments d ON u.dept_id = d.id – \u8fde\u63a5\u90e8\u95e8\u8868<\/li>\n\n\n\n
                            3. 3. WHERE u.status = ‘active’ AND d.budget > 100000 – \u8fc7\u6ee4\u6d3b\u8dc3\u7528\u6237\u548c\u9884\u7b97\u5145\u8db3\u7684\u90e8\u95e8<\/li>\n\n\n\n
                            4. 4. GROUP BY u.department – \u6309\u90e8\u95e8\u5206\u7ec4<\/li>\n\n\n\n
                            5. 5. HAVING AVG(u.salary) > 50000 – \u8fc7\u6ee4\u5e73\u5747\u5de5\u8d44\u8d85\u8fc75\u4e07\u7684\u90e8\u95e8<\/li>\n\n\n\n
                            6. 6. SELECT DISTINCT u.department, AVG(u.salary) – \u9009\u62e9\u90e8\u95e8\u548c\u5e73\u5747\u5de5\u8d44<\/li>\n\n\n\n
                            7. 7. DISTINCT – \u53bb\u91cd\uff08\u867d\u7136\u8fd9\u91ccGROUP BY\u5df2\u7ecf\u4fdd\u8bc1\u552f\u4e00\u6027\uff09<\/li>\n\n\n\n
                            8. 8. ORDER BY avg_salary DESC – \u6309\u5e73\u5747\u5de5\u8d44\u964d\u5e8f\u6392\u5217<\/li>\n\n\n\n
                            9. 9. LIMIT 5 – \u53ea\u53d6\u524d5\u6761\u8bb0\u5f55<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"
                              \u8f6c\u8f7d\uff1aMySQL\u67e5\u8be2\u6267\u884c\u987a\u5e8f\uff1a\u4e00\u5f20\u56fe\u770b\u61c2SQL\u662f\u5982\u4f55\u5de5\u4f5c\u7684 \ud83d\udd25 \u5f00\u7bc7\uff1a\u4e00\u4e2a\u8ba9\u4eba\u56f0\u60d1\u7684\u95ee\u9898 \u4f60\u5199\u7684SQL\u8bed\u53e5\u4e3a\u4ec0 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23],"tags":[],"_links":{"self":[{"href":"https:\/\/92it.top\/index.php?rest_route=\/wp\/v2\/posts\/18319"}],"collection":[{"href":"https:\/\/92it.top\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/92it.top\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/92it.top\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/92it.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=18319"}],"version-history":[{"count":2,"href":"https:\/\/92it.top\/index.php?rest_route=\/wp\/v2\/posts\/18319\/revisions"}],"predecessor-version":[{"id":18322,"href":"https:\/\/92it.top\/index.php?rest_route=\/wp\/v2\/posts\/18319\/revisions\/18322"}],"wp:attachment":[{"href":"https:\/\/92it.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=18319"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/92it.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=18319"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/92it.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=18319"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}