{"id":160067,"date":"2024-11-03T20:00:22","date_gmt":"2024-11-03T12:00:22","guid":{"rendered":"https:\/\/server.hk\/cnblog\/160067\/"},"modified":"2024-11-03T20:00:23","modified_gmt":"2024-11-03T12:00:23","slug":"oceanbase-%e6%95%99%e7%a8%8b%ef%bc%9aoceanbase-approx_count_distinct","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/160067\/","title":{"rendered":"OceanBase \u6559\u7a0b\uff1aOceanBase APPROX_COUNT_DISTINCT"},"content":{"rendered":"<h1 id=\"oceanbase-%e6%95%99%e7%a8%8b%ef%bc%9aoceanbase-approx_count_distinct-lOlyjMWazC\">OceanBase \u6559\u7a0b\uff1aOceanBase APPROX_COUNT_DISTINCT<\/h1>\n<p>\u5728\u5927\u6578\u64da\u8655\u7406\u548c\u5206\u6790\u4e2d\uff0c\u8a08\u7b97\u552f\u4e00\u503c\u7684\u6578\u91cf\u662f\u4e00\u500b\u5e38\u898b\u7684\u9700\u6c42\u3002\u50b3\u7d71\u7684\u8a08\u7b97\u65b9\u6cd5\u53ef\u80fd\u6703\u56e0\u70ba\u6578\u64da\u91cf\u9f90\u5927\u800c\u5c0e\u81f4\u6027\u80fd\u74f6\u9838\u3002\u70ba\u4e86\u89e3\u6c7a\u9019\u500b\u554f\u984c\uff0cOceanBase \u63d0\u4f9b\u4e86\u4e00\u500b\u9ad8\u6548\u7684\u89e3\u6c7a\u65b9\u6848\uff1a<code>APPROX_COUNT_DISTINCT<\/code> \u51fd\u6578\u3002\u672c\u6587\u5c07\u6df1\u5165\u63a2\u8a0e OceanBase \u7684 <code>APPROX_COUNT_DISTINCT<\/code> \u51fd\u6578\u7684\u4f7f\u7528\u65b9\u6cd5\u53ca\u5176\u512a\u52e2\u3002<\/p>\n<h2 id=\"%e4%bb%80%e9%ba%bc%e6%98%af-approx_count_distinct%ef%bc%9f-lOlyjMWazC\">\u4ec0\u9ebc\u662f APPROX_COUNT_DISTINCT\uff1f<\/h2>\n<p><code>APPROX_COUNT_DISTINCT<\/code> \u662f OceanBase \u4e2d\u7684\u4e00\u500b\u805a\u5408\u51fd\u6578\uff0c\u7528\u65bc\u5feb\u901f\u8a08\u7b97\u67d0\u500b\u5217\u4e2d\u552f\u4e00\u503c\u7684\u8fd1\u4f3c\u6578\u91cf\u3002\u9019\u500b\u51fd\u6578\u7279\u5225\u9069\u5408\u65bc\u8655\u7406\u5927\u6578\u64da\u96c6\uff0c\u56e0\u70ba\u5b83\u4f7f\u7528\u4e86\u6982\u7387\u7b97\u6cd5\u4f86\u4f30\u7b97\u552f\u4e00\u503c\u7684\u6578\u91cf\uff0c\u5f9e\u800c\u986f\u8457\u63d0\u9ad8\u4e86\u67e5\u8a62\u6027\u80fd\u3002<\/p>\n<h2 id=\"%e7%82%ba%e4%bb%80%e9%ba%bc%e4%bd%bf%e7%94%a8-approx_count_distinct%ef%bc%9f-lOlyjMWazC\">\u70ba\u4ec0\u9ebc\u4f7f\u7528 APPROX_COUNT_DISTINCT\uff1f<\/h2>\n<ul>\n<li><strong>\u6027\u80fd\u512a\u52e2\uff1a<\/strong>\u50b3\u7d71\u7684 <code>COUNT(DISTINCT column)<\/code> \u65b9\u6cd5\u5728\u8655\u7406\u5927\u91cf\u6578\u64da\u6642\u53ef\u80fd\u6703\u975e\u5e38\u7de9\u6162\uff0c\u800c <code>APPROX_COUNT_DISTINCT<\/code> \u901a\u904e\u4f7f\u7528\u54c8\u5e0c\u7b97\u6cd5\u548c\u96a8\u6a5f\u5316\u6280\u8853\uff0c\u80fd\u5920\u5728\u66f4\u77ed\u7684\u6642\u9593\u5167\u8fd4\u56de\u7d50\u679c\u3002<\/li>\n<li><strong>\u8cc7\u6e90\u7bc0\u7701\uff1a<\/strong>\u7531\u65bc\u5176\u9ad8\u6548\u7684\u8a08\u7b97\u65b9\u5f0f\uff0c<code>APPROX_COUNT_DISTINCT<\/code> \u53ef\u4ee5\u6e1b\u5c11\u5c0d\u8a08\u7b97\u8cc7\u6e90\u7684\u9700\u6c42\uff0c\u9019\u5c0d\u65bc\u8cc7\u6e90\u6709\u9650\u7684\u74b0\u5883\u5c24\u70ba\u91cd\u8981\u3002<\/li>\n<li><strong>\u53ef\u63a5\u53d7\u7684\u8aa4\u5dee\u7bc4\u570d\uff1a<\/strong>\u5728\u8a31\u591a\u61c9\u7528\u5834\u666f\u4e2d\uff0c\u5c0d\u65bc\u552f\u4e00\u503c\u7684\u7cbe\u78ba\u8a08\u7b97\u4e26\u4e0d\u662f\u5fc5\u9700\u7684\uff0c<code>APPROX_COUNT_DISTINCT<\/code> \u63d0\u4f9b\u7684\u8fd1\u4f3c\u503c\u901a\u5e38\u5df2\u7d93\u8db3\u5920\u6eff\u8db3\u696d\u52d9\u9700\u6c42\u3002<\/li>\n<\/ul>\n<h2 id=\"%e5%a6%82%e4%bd%95%e4%bd%bf%e7%94%a8-approx_count_distinct%ef%bc%9f-lOlyjMWazC\">\u5982\u4f55\u4f7f\u7528 APPROX_COUNT_DISTINCT\uff1f<\/h2>\n<p>\u4f7f\u7528 <code>APPROX_COUNT_DISTINCT<\/code> \u51fd\u6578\u975e\u5e38\u7c21\u55ae\uff0c\u4ee5\u4e0b\u662f\u57fa\u672c\u7684\u8a9e\u6cd5\uff1a<\/p>\n<pre><code>SELECT APPROX_COUNT_DISTINCT(column_name) FROM table_name;<\/code><\/pre>\n<p>\u4ee5\u4e0b\u662f\u4e00\u500b\u5177\u9ad4\u7684\u4f8b\u5b50\uff0c\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70ba <code>users<\/code> \u7684\u8868\uff0c\u4e26\u4e14\u6211\u5011\u60f3\u8981\u8a08\u7b97\u552f\u4e00\u7528\u6236\u7684\u6578\u91cf\uff1a<\/p>\n<pre><code>SELECT APPROX_COUNT_DISTINCT(user_id) AS unique_users FROM users;<\/code><\/pre>\n<p>\u9019\u689d\u67e5\u8a62\u5c07\u8fd4\u56de <code>user_id<\/code> \u5217\u4e2d\u552f\u4e00\u7528\u6236\u7684\u8fd1\u4f3c\u6578\u91cf\u3002<\/p>\n<h2 id=\"%e6%b3%a8%e6%84%8f%e4%ba%8b%e9%a0%85-lOlyjMWazC\">\u6ce8\u610f\u4e8b\u9805<\/h2>\n<p>\u96d6\u7136 <code>APPROX_COUNT_DISTINCT<\/code> \u63d0\u4f9b\u4e86\u986f\u8457\u7684\u6027\u80fd\u512a\u52e2\uff0c\u4f46\u5728\u4f7f\u7528\u6642\u4ecd\u9700\u6ce8\u610f\u4ee5\u4e0b\u5e7e\u9ede\uff1a<\/p>\n<ul>\n<li><strong>\u8aa4\u5dee\u7bc4\u570d\uff1a<\/strong>\u6839\u64da\u6578\u64da\u7684\u7279\u6027\uff0c<code>APPROX_COUNT_DISTINCT<\/code> \u7684\u7d50\u679c\u53ef\u80fd\u6703\u6709\u4e00\u5b9a\u7684\u8aa4\u5dee\u3002\u7528\u6236\u61c9\u6839\u64da\u5be6\u969b\u9700\u6c42\u8a55\u4f30\u9019\u4e00\u9ede\u3002<\/li>\n<li><strong>\u6578\u64da\u5206\u4f48\uff1a<\/strong>\u5982\u679c\u6578\u64da\u5206\u4f48\u4e0d\u5747\u52fb\uff0c\u53ef\u80fd\u6703\u5f71\u97ff\u8fd1\u4f3c\u8a08\u7b97\u7684\u6e96\u78ba\u6027\u3002<\/li>\n<li><strong>\u7248\u672c\u652f\u6301\uff1a<\/strong>\u78ba\u4fdd\u4f7f\u7528\u7684 OceanBase \u7248\u672c\u652f\u6301 <code>APPROX_COUNT_DISTINCT<\/code> \u51fd\u6578\u3002<\/li>\n<\/ul>\n<h2 id=\"%e7%b8%bd%e7%b5%90-lOlyjMWazC\">\u7e3d\u7d50<\/h2>\n<p>OceanBase \u7684 <code>APPROX_COUNT_DISTINCT<\/code> \u51fd\u6578\u662f\u4e00\u500b\u5f37\u5927\u7684\u5de5\u5177\uff0c\u80fd\u5920\u5728\u8655\u7406\u5927\u6578\u64da\u6642\u63d0\u4f9b\u9ad8\u6548\u7684\u552f\u4e00\u503c\u8a08\u7b97\u89e3\u6c7a\u65b9\u6848\u3002\u901a\u904e\u4f7f\u7528\u9019\u500b\u51fd\u6578\uff0c\u958b\u767c\u8005\u53ef\u4ee5\u5728\u4e0d\u5f71\u97ff\u6027\u80fd\u7684\u60c5\u6cc1\u4e0b\u7372\u5f97\u8fd1\u4f3c\u7684\u552f\u4e00\u503c\u8a08\u7b97\u7d50\u679c\uff0c\u5f9e\u800c\u66f4\u597d\u5730\u652f\u6301\u6578\u64da\u5206\u6790\u548c\u6c7a\u7b56\u904e\u7a0b\u3002<\/p>\n<p>\u5982\u679c\u60a8\u5c0d\u65bc <a href=\"https:\/\/server.hk\">VPS<\/a> \u89e3\u6c7a\u65b9\u6848\u611f\u8208\u8da3\uff0c\u6216\u60f3\u4e86\u89e3\u66f4\u591a\u95dc\u65bc <a href=\"https:\/\/server.hk\">\u9999\u6e2f\u4f3a\u670d\u5668<\/a> \u7684\u8cc7\u8a0a\uff0c\u6b61\u8fce\u8a2a\u554f\u6211\u5011\u7684\u7db2\u7ad9\u4ee5\u7372\u53d6\u66f4\u591a\u8a73\u7d30\u8cc7\u6599\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Learn how to use OceanBase&#8217;s APPROX_COUNT_DISTINCT function for efficient approximate counting in your database queries. Enhance your data analysis skills!<\/p>\n","protected":false},"author":0,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-160067","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/160067","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/types\/post"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=160067"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/160067\/revisions"}],"predecessor-version":[{"id":160068,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/160067\/revisions\/160068"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=160067"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=160067"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=160067"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}