{"id":1360,"date":"2024-08-07T19:12:10","date_gmt":"2024-08-07T11:12:10","guid":{"rendered":"https:\/\/blog.humh.cn\/?p=1360"},"modified":"2024-08-07T19:12:11","modified_gmt":"2024-08-07T11:12:11","slug":"hive-count%e4%b8%8ecollect_ws%e7%ad%89%e5%87%bd%e6%95%b0%e7%bb%93%e5%90%88%e4%bd%bf%e7%94%a8%e7%89%b9%e6%ae%8a%e7%bb%93%e6%9e%9c","status":"publish","type":"post","link":"https:\/\/blog.humh.cn\/?p=1360","title":{"rendered":"hive count\u4e0ecollect_ws\u7b49\u51fd\u6570\u7ed3\u5408\u4f7f\u7528\u7279\u6b8a\u7ed3\u679c"},"content":{"rendered":"\n<p>\u8fd9\u91cc\uff0c\u6211\u4eec\u9700\u8981\u5148\u4e86\u89e3\u5230 concat \u3001concat_ws \u7b49\u51fd\u6570\u5728\u4e00\u4e9b\u7279\u6b8a\u573a\u666f\u7684\u6267\u884c\u7ed3\u679c\u3002<\/p>\n\n\n\n<h3>concat<\/h3>\n\n\n\n<ul><li>\u53c2\u6570\u53ea\u6709 null<\/li><\/ul>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"shell\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">hive> select concat(null);\nNULL<\/pre>\n\n\n\n<ul><li>\u53c2\u6570\u4e2d\u5305\u542b\u6709 null<\/li><\/ul>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"shell\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">hive> select concat('1',null);\nNULL<\/pre>\n\n\n\n<h3>concat_ws<\/h3>\n\n\n\n<ul><li>\u9700\u62fc\u63a5\u6570\u7ec4\u4e3a null<\/li><\/ul>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"shell\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">hive> select concat_ws(',', null);\n<\/pre>\n\n\n\n<ul><li>\u9700\u62fc\u63a5\u6570\u7ec4\u4e3a\u7a7a\u6570\u7ec4<\/li><\/ul>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">hive> select concat_ws(',', array());\n<\/pre>\n\n\n\n<p>\u7ed3\u5408\u4e0a\u8ff0\u5185\u5bb9\uff0c\u6211\u4eec\u6765\u770b\u4e0b\u9762\u548c count \u51fd\u6570\u7ed3\u5408\u4f7f\u7528\u7684 case\u3002\uff08\u8fd9\u91cc\u6211\u4eec\u5df2\u77e5 count \u51fd\u6570\u8ba1\u7b97\u65f6\u4f1a\u8ba1\u5165 null \u7684\u884c\uff09<\/p>\n\n\n\n<h3>\u5f53 count \u53bb\u805a\u5408 concat_ws \u7a7a\u6570\u7ec4<\/h3>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"sql\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">with t as (\n    select concat_ws(',',array())\n)\nselect count(1) from t;\n-- \u6216\u4e0b\u9762\u4ee3\u7801\nwith t as (\n    select concat_ws(',',collect_list(null))\n)\nselect count(1) from t;<\/pre>\n\n\n\n<p>\u6267\u884c\u7ed3\u679c\u4e3a 1\uff0c\u800c\u975e\u6211\u4eec\u9884\u671f\u7684 0\u3002<\/p>\n\n\n\n<p>\u8fd9\u91cc\u53ef\u4ee5\u7406\u89e3\u4e3a concat_ws \u7a7a\u6570\u7ec4\u6216 null \u7684\u7ed3\u679c\u662f\u6709\u503c\u7684\uff0c\u53ea\u4e0d\u8fc7\u662f\u7a7a\u5b57\u7b26\u4e32\uff0c\u90a3\u4e48 count \u4e00\u6761\u7a7a\u5b57\u7b26\u4e32\u81ea\u7136\u662f 1\u3002<\/p>\n\n\n\n<h3>\u5f53 count \u53bb\u805a\u5408 concat_ws \u7a7a\u8bb0\u5f55<\/h3>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"sql\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">with t1 as (\n    select * from (\n        select 'a' as flag, 1 as tmp_col\n    ) tmp_t where flag != 'a'\n)\nselect count(*) from (\n    select concat_ws(',',collect_list(flag))\n    from t1\n) t2\n;<\/pre>\n\n\n\n<p>\u8fd9\u91cc\u663e\u7136 t1 \u8868\u7684\u7ed3\u679c\u662f\u7a7a\u7684\uff0c\u6ca1\u6570\u636e\u3002\u90a3\u4e48 collect_list(flag) \u5c31\u76f8\u5f53\u4e8e\u7a7a\u6570\u7ec4\uff0c\u7b49\u6548\u4e8e array()\uff0c\u90a3\u4e48\u518d\u88ab concat_ws \u8ba1\u7b97\u7684\u7ed3\u679c\u5c31\u662f\u7a7a\u5b57\u7b26\u4e32\u3002\u6700\u540e count \u81ea\u7136\u4e3a 1\u3002<\/p>\n\n\n\n<h3>\u57fa\u4e8e group by \u8fdb\u884c concat_ws\uff0c\u4e4b\u540e\u518d count<\/h3>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"sql\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\nwith t1 as (\n    select * from (\n        select 'a' as flag, 1 as tmp_col\n    ) tmp_t where flag != 'a'\n)\n \nselect count(*) from (\n    select concat_ws(',',collect_list(flag))\n    from t1\n    group by tmp_col\n) t2\n;<\/pre>\n\n\n\n<p>\u4e0a\u9762 sql \u6267\u884c\u7ed3\u679c\u4e3a 0\u3002<\/p>\n\n\n\n<p>\u8fd9\u91cc t1 \u8868\u7ed3\u679c\u662f\u7a7a\uff0c\u5373 tmp_col \u5b57\u6bb5\u6ca1\u6709\u4efb\u4f55\u6709\u6548\u503c\uff0c\u867d\u7136 collect_list \u4ecd\u662f\u7a7a\u6570\u7ec4\uff0c\u4f46\u56e0\u4e3a\u6709 group by \u7684\u9650\u5236\uff0c\u5219\u5b50\u8868 t2 \u662f\u4e00\u4e2a\u7a7a\u8868\uff0c\u800c\u975e\u4e00\u884c\u7a7a\u5b57\u7b26\u4e32\u3002\u6240\u4ee5 count \u7ed3\u679c\u4e3a 0\u3002<a href=\"https:\/\/confluence.colorv.com\/pages\/viewpage.action?pageId=93556535\"><\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u8fd9\u91cc\uff0c\u6211\u4eec\u9700\u8981\u5148\u4e86\u89e3\u5230 concat \u3001concat_ws \u7b49\u51fd\u6570\u5728\u4e00\u4e9b\u7279\u6b8a\u573a\u666f\u7684\u6267\u884c\u7ed3\u679c\u3002 concat \u53c2 [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[129],"tags":[120],"_links":{"self":[{"href":"https:\/\/blog.humh.cn\/index.php?rest_route=\/wp\/v2\/posts\/1360"}],"collection":[{"href":"https:\/\/blog.humh.cn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.humh.cn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.humh.cn\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.humh.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1360"}],"version-history":[{"count":1,"href":"https:\/\/blog.humh.cn\/index.php?rest_route=\/wp\/v2\/posts\/1360\/revisions"}],"predecessor-version":[{"id":1361,"href":"https:\/\/blog.humh.cn\/index.php?rest_route=\/wp\/v2\/posts\/1360\/revisions\/1361"}],"wp:attachment":[{"href":"https:\/\/blog.humh.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1360"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.humh.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1360"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.humh.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1360"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}