{"id":1708,"date":"2025-02-16T08:37:02","date_gmt":"2025-02-16T00:37:02","guid":{"rendered":"https:\/\/www.laixuexila.com\/?p=1708"},"modified":"2025-02-16T08:37:02","modified_gmt":"2025-02-16T00:37:02","slug":"avg-%e5%87%bd%e6%95%b0%e5%b8%b8%e8%a7%81%e9%97%ae%e9%a2%98%e5%8f%8a%e8%a7%a3%e5%86%b3%e6%8c%87%e5%8d%97","status":"publish","type":"post","link":"https:\/\/www.laixuexila.com\/index.php\/2025\/02\/16\/avg-%e5%87%bd%e6%95%b0%e5%b8%b8%e8%a7%81%e9%97%ae%e9%a2%98%e5%8f%8a%e8%a7%a3%e5%86%b3%e6%8c%87%e5%8d%97\/","title":{"rendered":"AVG() \u51fd\u6570\u5e38\u89c1\u95ee\u9898\u53ca\u89e3\u51b3\u6307\u5357"},"content":{"rendered":"\n

AVG()<\/code> \u51fd\u6570\u7528\u4e8e\u8ba1\u7b97\u5217\u4e2d\u7684\u5e73\u5747\u503c\uff0c\u4f46\u5728\u5b9e\u9645\u4f7f\u7528\u8fc7\u7a0b\u4e2d\u4e5f\u53ef\u80fd\u9047\u5230\u4e00\u4e9b\u5e38\u89c1\u95ee\u9898\u3002\u4e0b\u9762\u662f\u4e00\u4e9b\u5e38\u89c1\u95ee\u9898\u4ee5\u53ca\u76f8\u5e94\u7684\u89e3\u51b3\u6307\u5357\uff0c\u5e2e\u52a9\u4f60\u66f4\u597d\u5730\u7406\u89e3\u548c\u4f7f\u7528 AVG()<\/code> \u51fd\u6570\u3002<\/p>\n\n\n\n

1. \u95ee\u9898\uff1aAVG()<\/code> \u8ba1\u7b97\u7ed3\u679c\u4e0d\u51c6\u786e\uff08\u5ffd\u7565\u4e86 NULL<\/code> \u503c\uff09<\/strong><\/h3>\n\n\n\n

\u539f\u56e0\uff1a<\/h4>\n\n\n\n

AVG()<\/code> \u51fd\u6570\u4f1a\u81ea\u52a8\u5ffd\u7565 NULL<\/code> \u503c\uff0c\u8fd9\u610f\u5473\u7740\u5982\u679c\u5217\u4e2d\u6709 NULL<\/code>\uff0c\u5b83\u4e0d\u4f1a\u7b97\u5165\u5e73\u5747\u503c\u7684\u8ba1\u7b97\u4e2d\u3002\u4f60\u53ef\u80fd\u4f1a\u89c9\u5f97\u7ed3\u679c\u4e0d\u51c6\u786e\uff0c\u4f46\u5176\u5b9e\u662f\u56e0\u4e3a\u8fd9\u4e9b NULL<\/code> \u503c\u88ab\u6392\u9664\u4e86\u3002<\/p>\n\n\n\n

\u89e3\u51b3\u65b9\u6848\uff1a<\/h4>\n\n\n\n

\u5982\u679c\u4f60\u5e0c\u671b\u5c06 NULL<\/code> \u503c\u4f5c\u4e3a 0 \u6765\u53c2\u4e0e\u8ba1\u7b97\uff08\u5373\u89c6\u4e3a 0\uff09\uff0c\u53ef\u4ee5\u4f7f\u7528 COALESCE()<\/code> \u51fd\u6570\u6216 CASE<\/code> \u8868\u8fbe\u5f0f\u5c06 NULL<\/code> \u8f6c\u6362\u4e3a 0\uff0c\u4f8b\u5982\uff1a<\/p>\n\n\n\n

SELECT AVG(COALESCE(salary, 0)) AS avg_salary\nFROM employees;<\/code><\/pre>\n\n\n\n
\u6216\u8005\uff1a<\/p>\n\n\n\n
SELECT AVG(CASE WHEN salary IS NULL THEN 0 ELSE salary END) AS avg_salary\nFROM employees;<\/code><\/pre>\n\n\n\n
\u8fd9\u6837\uff0cNULL<\/code> \u503c\u5c31\u4f1a\u88ab\u89c6\u4e3a 0 \u6765\u53c2\u4e0e\u5e73\u5747\u503c\u7684\u8ba1\u7b97\u3002<\/p>\n\n\n\n
2. \u95ee\u9898\uff1a\u4f7f\u7528 AVG()<\/code> \u65f6\u8fd4\u56de NULL<\/code><\/strong><\/h3>\n\n\n\n
\u539f\u56e0\uff1a<\/h4>\n\n\n\n
\u5982\u679c\u8ba1\u7b97\u7684\u5217\u4e2d\u6ca1\u6709\u7b26\u5408\u6761\u4ef6\u7684\u975e NULL<\/code> \u503c\uff0cAVG()<\/code> \u51fd\u6570\u5c06\u8fd4\u56de NULL<\/code>\u3002\u4f8b\u5982\uff0c\u5f53\u4f60\u5728 WHERE<\/code> \u5b50\u53e5\u4e2d\u8fc7\u6ee4\u4e86\u6240\u6709\u6570\u636e\u65f6\uff0c\u7ed3\u679c\u53ef\u80fd\u662f NULL<\/code>\u3002<\/p>\n\n\n\n
\u89e3\u51b3\u65b9\u6848\uff1a<\/h4>\n\n\n\n
    \n
  • \u786e\u4fdd WHERE<\/code> \u5b50\u53e5\u7684\u6761\u4ef6\u4e0d\u4f1a\u8fc7\u6ee4\u6389\u6240\u6709\u6570\u636e\u3002\u5982\u679c\u9700\u8981\uff0c\u4f60\u53ef\u4ee5\u6dfb\u52a0\u6761\u4ef6\u6765\u907f\u514d\u8fd9\u79cd\u60c5\u51b5\u3002<\/li>\n\n\n\n
  • \u5982\u679c\u4f60\u5e0c\u671b NULL<\/code> \u7ed3\u679c\u8f6c\u5316\u4e3a 0\uff0c\u53ef\u4ee5\u4f7f\u7528 COALESCE()<\/code> \u51fd\u6570\uff1a<\/li>\n<\/ul>\n\n\n\n
    SELECT COALESCE(AVG(salary), 0) AS avg_salary\nFROM employees\nWHERE department = 'Sales';<\/code><\/pre>\n\n\n\n
    \u8fd9\u6837\uff0c\u5373\u4f7f\u6ca1\u6709\u7b26\u5408\u6761\u4ef6\u7684\u6570\u636e\uff0cAVG()<\/code> \u51fd\u6570\u4e5f\u4f1a\u8fd4\u56de 0<\/code>\u3002<\/p>\n\n\n\n
    3. \u95ee\u9898\uff1aAVG()<\/code> \u7ed3\u679c\u4e0e\u9884\u671f\u4e0d\u7b26\uff0c\u53ef\u80fd\u7531\u4e8e\u6570\u636e\u7684\u5f02\u5e38\u503c<\/strong><\/h3>\n\n\n\n
    \u539f\u56e0\uff1a<\/h4>\n\n\n\n
    \u5982\u679c\u6570\u636e\u4e2d\u5305\u542b\u5f02\u5e38\u503c\uff08\u4f8b\u5982\u6781\u9ad8\u6216\u6781\u4f4e\u7684\u503c\uff09\uff0c\u53ef\u80fd\u4f1a\u5bf9\u5e73\u5747\u503c\u4ea7\u751f\u8f83\u5927\u5f71\u54cd\uff0c\u5bfc\u81f4\u7ed3\u679c\u504f\u79bb\u6b63\u5e38\u8303\u56f4\u3002<\/p>\n\n\n\n
    \u89e3\u51b3\u65b9\u6848\uff1a<\/h4>\n\n\n\n
      \n
    • \u5728\u4f7f\u7528 AVG()<\/code> \u65f6\uff0c\u53ef\u4ee5\u5148\u5206\u6790\u6570\u636e\uff0c\u627e\u51fa\u5e76\u6392\u9664\u5f02\u5e38\u503c\u3002\u4f8b\u5982\uff0c\u4f7f\u7528 WHERE<\/code> \u5b50\u53e5\u8fc7\u6ee4\u6389\u4e0d\u5408\u7406\u7684\u503c\uff1a<\/li>\n<\/ul>\n\n\n\n
      SELECT AVG(salary) AS avg_salary\nFROM employees\nWHERE salary BETWEEN 3000 AND 10000;  -- \u6392\u9664\u6781\u7aef\u503c<\/code><\/pre>\n\n\n\n
        \n
      • \u53e6\u4e00\u79cd\u65b9\u6cd5\u662f\u8ba1\u7b97 AVG()<\/code> \u540e\u4f7f\u7528 STDEV()<\/code> \u6216 VARIANCE()<\/code> \u7b49\u7edf\u8ba1\u51fd\u6570\uff0c\u627e\u51fa\u6570\u636e\u7684\u6ce2\u52a8\u8303\u56f4\uff0c\u5e2e\u52a9\u4f60\u7406\u89e3\u7ed3\u679c\u3002<\/li>\n<\/ul>\n\n\n\n
        4. \u95ee\u9898\uff1aAVG()<\/code> \u548c GROUP BY<\/code> \u914d\u5408\u4f7f\u7528\u65f6\uff0c\u8fd4\u56de\u503c\u4e0d\u4e00\u81f4<\/strong><\/h3>\n\n\n\n
        \u539f\u56e0\uff1a<\/h4>\n\n\n\n
        \u5728 GROUP BY<\/code> \u4e2d\u4f7f\u7528 AVG()<\/code> \u65f6\uff0c\u5982\u679c\u67d0\u4e9b\u5206\u7ec4\u6ca1\u6709\u6570\u636e\uff0c\u53ef\u80fd\u4f1a\u5bfc\u81f4\u8fd9\u4e9b\u5206\u7ec4\u4e22\u5931\uff0c\u6216\u8005\u8fd4\u56de\u503c\u4f4e\u4e8e\u9884\u671f\u3002<\/p>\n\n\n\n
        \u89e3\u51b3\u65b9\u6848\uff1a<\/h4>\n\n\n\n
          \n
        • \u4f7f\u7528 HAVING<\/code> \u5b50\u53e5\u6765\u786e\u4fdd\u53ea\u8fd4\u56de\u7b26\u5408\u6761\u4ef6\u7684\u5206\u7ec4\u3002\u4f8b\u5982\uff0c\u8ba1\u7b97\u6bcf\u4e2a\u90e8\u95e8\u7684\u5e73\u5747\u5de5\u8d44\uff0c\u5e76\u786e\u4fdd\u53ea\u6709\u5458\u5de5\u6570\u5927\u4e8e 0 \u7684\u90e8\u95e8\u624d\u663e\u793a\uff1a<\/li>\n<\/ul>\n\n\n\n
          SELECT department, AVG(salary) AS avg_salary\nFROM employees\nGROUP BY department\nHAVING COUNT(*) > 0;<\/code><\/pre>\n\n\n\n
          5. \u95ee\u9898\uff1a\u8ba1\u7b97\u5e73\u5747\u503c\u65f6\uff0c\u5305\u542b\u4e86\u4e0d\u9700\u8981\u7684\u6570\u636e<\/strong><\/h3>\n\n\n\n
          \u539f\u56e0\uff1a<\/h4>\n\n\n\n
          \u5982\u679c\u4f60\u7684\u6570\u636e\u8868\u4e2d\u6709\u4e00\u4e9b\u4f60\u4e0d\u5e0c\u671b\u53c2\u4e0e\u8ba1\u7b97\u7684\u884c\uff0c\u6bd4\u5982\u4e00\u4e9b\u6807\u8bb0\u4e3a “\u65e0\u6548” \u6216 “\u6682\u65f6” \u7684\u8bb0\u5f55\uff0cAVG()<\/code> \u4f1a\u9ed8\u8ba4\u5c06\u8fd9\u4e9b\u8bb0\u5f55\u4e5f\u7b97\u5165\u5e73\u5747\u503c\u3002<\/p>\n\n\n\n
          \u89e3\u51b3\u65b9\u6848\uff1a<\/h4>\n\n\n\n
            \n
          • \u901a\u8fc7 WHERE<\/code> \u5b50\u53e5\u8fc7\u6ee4\u6389\u4e0d\u9700\u8981\u7684\u8bb0\u5f55\uff0c\u4f8b\u5982\uff0c\u6392\u9664\u72b6\u6001\u4e3a “\u65e0\u6548” \u7684\u5458\u5de5\uff1a<\/li>\n<\/ul>\n\n\n\n
            SELECT AVG(salary) AS avg_salary\nFROM employees\nWHERE status != 'inactive';  -- \u6392\u9664\u65e0\u6548\u7684\u8bb0\u5f55<\/code><\/pre>\n\n\n\n
            6. \u95ee\u9898\uff1aAVG()<\/code> \u7ed3\u679c\u51fa\u73b0\u56db\u820d\u4e94\u5165\u8bef\u5dee<\/strong><\/h3>\n\n\n\n
            \u539f\u56e0\uff1a<\/h4>\n\n\n\n
            \u7531\u4e8e\u6d6e\u52a8\u7cbe\u5ea6\uff0cAVG()<\/code> \u51fd\u6570\u8ba1\u7b97\u51fa\u7684\u5e73\u5747\u503c\u53ef\u80fd\u4f1a\u6709\u56db\u820d\u4e94\u5165\u7684\u8bef\u5dee\uff0c\u7279\u522b\u662f\u5f53\u6d89\u53ca\u5c0f\u6570\u65f6\u3002<\/p>\n\n\n\n
            \u89e3\u51b3\u65b9\u6848\uff1a<\/h4>\n\n\n\n
            \u4f60\u53ef\u4ee5\u4f7f\u7528 ROUND()<\/code> \u51fd\u6570\u6765\u63a7\u5236\u7ed3\u679c\u7684\u5c0f\u6570\u4f4d\u6570\u3002\u4f8b\u5982\uff0c\u56db\u820d\u4e94\u5165\u5230 2 \u4f4d\u5c0f\u6570\uff1a<\/p>\n\n\n\n
            SELECT ROUND(AVG(salary), 2) AS avg_salary\nFROM employees;<\/code><\/pre>\n\n\n\n
            7. \u95ee\u9898\uff1a\u5728 AVG()<\/code> \u4e2d\u5305\u542b\u4e86\u9519\u8bef\u7684\u6570\u636e\u7c7b\u578b<\/strong><\/h3>\n\n\n\n
            \u539f\u56e0\uff1a<\/h4>\n\n\n\n
            AVG()<\/code> \u51fd\u6570\u53ea\u9002\u7528\u4e8e\u6570\u503c\u7c7b\u578b\u7684\u5b57\u6bb5\u3002\u5982\u679c\u4f60\u5c06\u6587\u672c\u6216\u65e5\u671f\u7c7b\u578b\u7684\u5b57\u6bb5\u4f20\u9012\u7ed9 AVG()<\/code>\uff0c\u4f1a\u5bfc\u81f4\u9519\u8bef\u3002<\/p>\n\n\n\n
            \u89e3\u51b3\u65b9\u6848\uff1a<\/h4>\n\n\n\n
              \n
            • \u786e\u4fdd\u4f20\u9012\u7ed9 AVG()<\/code> \u7684\u5b57\u6bb5\u662f\u6570\u503c\u7c7b\u578b\uff08\u5982 INT<\/code>\u3001DECIMAL<\/code>\u3001FLOAT<\/code> \u7b49\uff09\u3002<\/li>\n\n\n\n
            • \u5982\u679c\u4f60\u5728\u8ba1\u7b97\u4e2d\u6d89\u53ca\u65e5\u671f\u5b57\u6bb5\uff0c\u5e76\u4e14\u9700\u8981\u8ba1\u7b97\u67d0\u4e2a\u5b57\u6bb5\u7684\u65f6\u95f4\u5dee\u7684\u5e73\u5747\u503c\uff0c\u53ef\u4ee5\u5148\u4f7f\u7528\u65e5\u671f\u51fd\u6570\u5c06\u65e5\u671f\u8f6c\u6362\u4e3a\u5929\u6570\u6216\u5176\u4ed6\u5355\u4f4d\u3002\u4f8b\u5982\uff0c\u8ba1\u7b97\u5458\u5de5\u5165\u804c\u65f6\u95f4\u7684\u5e73\u5747\u5929\u6570\uff1a<\/li>\n<\/ul>\n\n\n\n
              SELECT AVG(DATEDIFF(CURRENT_DATE, hire_date)) AS avg_days\nFROM employees;<\/code><\/pre>\n\n\n\n
              8. \u95ee\u9898\uff1a\u5bf9\u5927\u6570\u636e\u96c6\u4f7f\u7528 AVG()<\/code> \u65f6\u6027\u80fd\u8f83\u5dee<\/strong><\/h3>\n\n\n\n
              \u539f\u56e0\uff1a<\/h4>\n\n\n\n
              AVG()<\/code> \u51fd\u6570\u9700\u8981\u5bf9\u5927\u91cf\u6570\u636e\u8fdb\u884c\u8ba1\u7b97\uff0c\u5c24\u5176\u662f\u5728\u6ca1\u6709\u9002\u5f53\u7d22\u5f15\u65f6\uff0c\u6027\u80fd\u53ef\u80fd\u4f1a\u53d7\u5230\u5f71\u54cd\u3002\u5927\u6570\u636e\u96c6\u8ba1\u7b97\u5e73\u5747\u503c\u53ef\u80fd\u4f1a\u6d88\u8017\u5927\u91cf\u7684\u65f6\u95f4\u548c\u8d44\u6e90\u3002<\/p>\n\n\n\n
              \u89e3\u51b3\u65b9\u6848\uff1a<\/h4>\n\n\n\n
                \n
              • \u786e\u4fdd\u5bf9\u76f8\u5173\u5217\u5efa\u7acb\u7d22\u5f15\uff0c\u5c24\u5176\u662f\u53c2\u4e0e\u8ba1\u7b97\u7684\u5b57\u6bb5\u3002\u5982\u679c WHERE<\/code> \u5b50\u53e5\u4e2d\u6d89\u53ca\u7684\u5217\u6ca1\u6709\u7d22\u5f15\uff0c\u8003\u8651\u6dfb\u52a0\u7d22\u5f15\u4ee5\u52a0\u901f\u67e5\u8be2\u3002<\/li>\n\n\n\n
              • \u5982\u679c\u53ef\u80fd\u7684\u8bdd\uff0c\u5c06\u6570\u636e\u6309\u4e00\u5b9a\u6761\u4ef6\u5206\u6279\u5904\u7406\uff0c\u51cf\u5c11\u6bcf\u6b21\u8ba1\u7b97\u7684\u8d1f\u8f7d\u3002<\/li>\n<\/ul>\n\n\n\n
                \u603b\u7ed3<\/h3>\n\n\n\n
                AVG()<\/code> \u51fd\u6570\u5728\u8ba1\u7b97\u5e73\u5747\u503c\u65f6\u6709\u5f88\u591a\u5e38\u89c1\u7684\u95ee\u9898\uff0c\u901a\u5e38\u4e0e NULL<\/code> \u503c\u3001\u5f02\u5e38\u503c\u3001\u6570\u636e\u7c7b\u578b\u3001\u8fc7\u6ee4\u6761\u4ef6\u7b49\u56e0\u7d20\u6709\u5173\u3002\u7406\u89e3\u8fd9\u4e9b\u95ee\u9898\u5e76\u91c7\u53d6\u76f8\u5e94\u7684\u89e3\u51b3\u65b9\u6848\uff0c\u80fd\u591f\u5e2e\u52a9\u4f60\u66f4\u6709\u6548\u5730\u4f7f\u7528 AVG()<\/code> \u51fd\u6570\uff0c\u5f97\u51fa\u66f4\u51c6\u786e\u548c\u6709\u610f\u4e49\u7684\u7ed3\u679c\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
                AVG() \u51fd\u6570\u7528\u4e8e\u8ba1\u7b97\u5217\u4e2d\u7684\u5e73\u5747\u503c\uff0c\u4f46\u5728\u5b9e\u9645\u4f7f\u7528\u8fc7\u7a0b\u4e2d\u4e5f\u53ef\u80fd\u9047\u5230\u4e00\u4e9b\u5e38\u89c1\u95ee\u9898\u3002\u4e0b\u9762\u662f\u4e00\u4e9b\u5e38\u89c1\u95ee\u9898\u4ee5\u53ca\u76f8\u5e94\u7684\u89e3 […]<\/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-1708","post","type-post","status-publish","format-standard","hentry","category-sql"],"_links":{"self":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/1708","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=1708"}],"version-history":[{"count":1,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/1708\/revisions"}],"predecessor-version":[{"id":1709,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/1708\/revisions\/1709"}],"wp:attachment":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media?parent=1708"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/categories?post=1708"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/tags?post=1708"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}