{"id":40358,"date":"2023-07-30T02:58:51","date_gmt":"2023-07-29T18:58:51","guid":{"rendered":"https:\/\/docs.pingcode.com\/?p=40358"},"modified":"2023-07-30T02:58:53","modified_gmt":"2023-07-29T18:58:53","slug":"%e6%89%a7%e8%a1%8ccount1%e3%80%81count-%e4%b8%8e-count%e5%88%97%e5%90%8d-%e5%88%b0%e5%ba%95%e6%9c%89%e4%bb%80%e4%b9%88%e5%8c%ba%e5%88%ab","status":"publish","type":"post","link":"https:\/\/docs.pingcode.com\/ask\/40358.html","title":{"rendered":"\u6267\u884ccount(1)\u3001count(*) \u4e0e count(\u5217\u540d) \u5230\u5e95\u6709\u4ec0\u4e48\u533a\u522b"},"content":{"rendered":"\n
\n

\u6267\u884ccount(1)\u3001count(*) \u4e0e count(\u5217\u540d) \u7684\u533a\u522b\uff1a\u4e00\u3001\u8bed\u4e49\u4e0d\u540c\uff1b\u4e8c\u3001\u6027\u80fd\u5dee\u5f02\uff1b\u4e09\u3001\u5bf9\u7a7a\u503c\u7684\u5904\u7406\u4e0d\u540c\uff1b\u56db\u3001\u4f7f\u7528\u8303\u56f4\u4e0d\u540c\uff1b\u4e94\u3001\u7ed3\u679c\u96c6\u4e0d\u540c\uff1b\u516d\u3001\u53ef\u8bfb\u6027\u4e0d\u540c\u3002\u8bed\u4e49\u4e0d\u540c\u662f\u6307\uff0ccount(1)\u8868\u793a\u7edf\u8ba1\u67e5\u8be2\u7ed3\u679c\u7684\u884c\u6570\uff0ccount(*)\u8868\u793a\u7edf\u8ba1\u67e5\u8be2\u7ed3\u679c\u7684\u884c\u6570\uff0ccount(\u5217\u540d)\u8868\u793a\u7edf\u8ba1\u6307\u5b9a\u5217\u7684\u975e\u7a7a\u503c\u7684\u6570\u91cf\u3002<\/p>\n<\/blockquote>\n\n\n

\n
\"\"<\/figure><\/div>\n\n\n

\u4e00\u3001\u8bed\u4e49\u4e0d\u540c<\/h2>\n\n\n\n
    \n
  • count(1)\uff1a\u8868\u793a\u7edf\u8ba1\u67e5\u8be2\u7ed3\u679c\u7684\u884c\u6570\uff0c\u4e0d\u8003\u8651\u8868\u4e2d\u7684\u4efb\u4f55\u5217\u7684\u503c\uff0c\u53ea\u5173\u5fc3\u662f\u5426\u5b58\u5728\u884c\u3002<\/li>\n\n\n\n
  • count(*)\uff1a\u8868\u793a\u7edf\u8ba1\u67e5\u8be2\u7ed3\u679c\u7684\u884c\u6570\uff0c\u4e0ecount(1)\u7c7b\u4f3c\uff0c\u4e0d\u8003\u8651\u8868\u4e2d\u7684\u4efb\u4f55\u5217\u7684\u503c\uff0c\u53ea\u5173\u5fc3\u662f\u5426\u5b58\u5728\u884c\u3002<\/li>\n\n\n\n
  • count(\u5217\u540d)\uff1a\u8868\u793a\u7edf\u8ba1\u6307\u5b9a\u5217\u7684\u975e\u7a7a\u503c\u7684\u6570\u91cf\uff0c\u53ea\u7edf\u8ba1\u6307\u5b9a\u5217\u4e2d\u4e0d\u4e3aNULL\u7684\u884c\u3002<\/li>\n<\/ul>\n\n\n\n

    \u4e8c\u3001\u6027\u80fd\u5dee\u5f02<\/h2>\n\n\n\n
      \n
    • count(1)\u548ccount(*)\uff1a\u8fd9\u4e24\u79cd\u5199\u6cd5\u5728\u5927\u591a\u6570\u6570\u636e\u5e93\u7cfb\u7edf\u4e2d\u7684\u6027\u80fd\u662f\u76f8\u540c\u7684\uff0c\u56e0\u4e3a\u5b83\u4eec\u90fd\u4e0d\u5173\u5fc3\u5177\u4f53\u7684\u5217\u503c\uff0c\u53ea\u5173\u5fc3\u884c\u7684\u5b58\u5728\u4e0e\u5426\u3002<\/li>\n\n\n\n
    • count(\u5217\u540d)\uff1a\u8fd9\u79cd\u5199\u6cd5\u5728\u67d0\u4e9b\u6570\u636e\u5e93\u7cfb\u7edf\u4e2d\u53ef\u80fd\u4f1a\u6bd4count(1)\u548ccount(*)\u6027\u80fd\u7a0d\u5dee\uff0c\u56e0\u4e3a\u5b83\u9700\u8981\u68c0\u67e5\u6307\u5b9a\u5217\u7684\u503c\u662f\u5426\u4e3aNULL\uff0c\u5e76\u6392\u9664NULL\u503c\u7684\u884c\u3002<\/li>\n<\/ul>\n\n\n\n

      \u4e09\u3001\u5bf9\u7a7a\u503c\u7684\u5904\u7406\u4e0d\u540c<\/h2>\n\n\n\n
        \n
      • count(1)\u548ccount(*)\uff1a\u4e0d\u5173\u5fc3\u8868\u4e2d\u7684\u5177\u4f53\u5217\u503c\uff0c\u56e0\u6b64\u4e0d\u53d7\u7a7a\u503c\u5f71\u54cd\uff0c\u4f1a\u5c06\u5305\u542bNULL\u503c\u7684\u884c\u4e5f\u8ba1\u7b97\u5728\u5185\u3002<\/li>\n\n\n\n
      • count(\u5217\u540d)\uff1a\u53ea\u7edf\u8ba1\u6307\u5b9a\u5217\u7684\u975e\u7a7a\u503c\uff0c\u4f1a\u6392\u9664\u5305\u542bNULL\u503c\u7684\u884c\uff0c\u53ea\u8ba1\u7b97\u6307\u5b9a\u5217\u4e2d\u4e0d\u4e3aNULL\u7684\u884c<\/li>\n<\/ul>\n\n\n\n

        \u56db\u3001\u4f7f\u7528\u8303\u56f4\u4e0d\u540c<\/h2>\n\n\n\n
          \n
        • count(1)\u548ccount(*)\uff1a\u9002\u7528\u4e8e\u67e5\u8be2\u6574\u4e2a\u8868\u6216\u6ee1\u8db3\u7279\u5b9a\u6761\u4ef6\u7684\u884c\u6570\u3002<\/li>\n\n\n\n
        • count(\u5217\u540d)\uff1a\u9002\u7528\u4e8e\u7edf\u8ba1\u7279\u5b9a\u5217\u7684\u975e\u7a7a\u503c\u6570\u91cf\u3002<\/li>\n<\/ul>\n\n\n\n

          \u4e94\u3001\u7ed3\u679c\u96c6\u4e0d\u540c<\/h2>\n\n\n\n
            \n
          • count(1)\u548ccount(*)\uff1a\u8fd4\u56de\u7684\u7ed3\u679c\u96c6\u53ea\u6709\u4e00\u884c\u4e00\u5217\uff0c\u5373\u8868\u793a\u67e5\u8be2\u7ed3\u679c\u7684\u884c\u6570\u3002<\/li>\n\n\n\n
          • count(\u5217\u540d)\uff1a\u8fd4\u56de\u7684\u7ed3\u679c\u96c6\u53ea\u6709\u4e00\u884c\u4e00\u5217\uff0c\u5373\u8868\u793a\u6307\u5b9a\u5217\u7684\u975e\u7a7a\u503c\u6570\u91cf\u3002<\/li>\n<\/ul>\n\n\n\n

            \u516d\u3001\u53ef\u8bfb\u6027\u4e0d\u540c<\/h2>\n\n\n\n
              \n
            • count(1)\uff1a\u8bed\u4e49\u4e0a\u4e0d\u591f\u660e\u786e\uff0c\u4e0d\u5bb9\u6613\u7406\u89e3\u5176\u4f5c\u7528\u3002<\/li>\n\n\n\n
            • count(*)\uff1a\u8bed\u4e49\u660e\u786e\uff0c\u8868\u793a\u7edf\u8ba1\u884c\u6570\u3002<\/li>\n\n\n\n
            • count(\u5217\u540d)\uff1a\u8bed\u4e49\u660e\u786e\uff0c\u8868\u793a\u7edf\u8ba1\u6307\u5b9a\u5217\u7684\u975e\u7a7a\u503c\u6570\u91cf\u3002<\/li>\n<\/ul>\n\n\n\n

              \u5ef6\u4f38\u9605\u8bfb<\/strong><\/h2>\n\n\n\n

              COUNT(*)\u662f\u4ec0\u4e48<\/strong><\/p>\n\n\n\n

              COUNT(*) \u662f\u4e00\u79cd\u6570\u636e\u5e93\u67e5\u8be2\u8bed\u53e5\uff0c\u7528\u4e8e\u7edf\u8ba1\u67d0\u4e2a\u8868\u4e2d\u7684\u8bb0\u5f55\u6570\u6216\u6ee1\u8db3\u6307\u5b9a\u6761\u4ef6\u7684\u8bb0\u5f55\u6570\u3002\u5b83\u8fd4\u56de\u4e00\u4e2a\u8868\u793a\u8bb0\u5f55\u6570\u91cf\u7684\u6574\u6570\u503c\u3002\u4f7f\u7528 COUNT() \u65f6\uff0c\u6570\u636e\u5e93\u5f15\u64ce\u4f1a\u5bf9\u6307\u5b9a\u7684\u8868\u8fdb\u884c\u626b\u63cf\uff0c\u5e76\u8ba1\u7b97\u7b26\u5408\u6761\u4ef6\u7684\u8bb0\u5f55\u6570\u91cf\u3002 \u8868\u793a\u9009\u62e9\u6240\u6709\u7684\u5217\uff0c\u800c\u4e0d\u662f\u7279\u5b9a\u7684\u5217\u540d\u3002\u56e0\u6b64\uff0cCOUNT(*) \u5c06\u7edf\u8ba1\u6574\u4e2a\u8868\u4e2d\u7684\u8bb0\u5f55\u6570\uff0c\u65e0\u8bba\u5177\u4f53\u7684\u5217\u503c\u662f\u4ec0\u4e48\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"\u6267\u884ccount(1)\u3001count(*) \u4e0e count(\u5217\u540d) \u7684\u533a\u522b\uff1a\u4e00\u3001\u8bed\u4e49\u4e0d\u540c\uff1b\u4e8c\u3001\u6027\u80fd\u5dee\u5f02\uff1b\u4e09\u3001\u5bf9\u7a7a\u503c […]","protected":false},"author":1,"featured_media":40359,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[37],"tags":[119],"acf":[],"_links":{"self":[{"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/posts\/40358"}],"collection":[{"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/comments?post=40358"}],"version-history":[{"count":0,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/posts\/40358\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/media\/40359"}],"wp:attachment":[{"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/media?parent=40358"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/categories?post=40358"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/docs.pingcode.com\/wp-json\/wp\/v2\/tags?post=40358"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}