{"id":165365,"date":"2024-11-05T11:48:38","date_gmt":"2024-11-05T03:48:38","guid":{"rendered":"https:\/\/server.hk\/cnblog\/165365\/"},"modified":"2024-11-05T11:48:38","modified_gmt":"2024-11-05T03:48:38","slug":"%e7%a9%ba%e6%a0%bc%e6%98%af%e5%93%aa%e7%a8%ae%e6%95%b8%e6%93%9a%e5%ba%ab%e9%a1%9e%e5%9e%8b%ef%bc%9f-%e7%a9%ba%e6%a0%bc%e5%b1%ac%e6%96%bc%e4%bb%80%e9%ba%bc%e5%9e%8b%e6%95%b8%e6%93%9a%e5%ba%ab","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/165365\/","title":{"rendered":"\u7a7a\u683c\u662f\u54ea\u7a2e\u6578\u64da\u5eab\u985e\u578b\uff1f (\u7a7a\u683c\u5c6c\u65bc\u4ec0\u9ebc\u578b\u6578\u64da\u5eab)"},"content":{"rendered":"

\u7a7a\u683c\u662f\u54ea\u7a2e\u6578\u64da\u5eab\u985e\u578b\uff1f<\/h1>\n

\u5728\u7576\u4eca\u7684\u6578\u64da\u7ba1\u7406\u4e16\u754c\u4e2d\uff0c\u6578\u64da\u5eab\u7684\u985e\u578b\u591a\u7a2e\u591a\u6a23\uff0c\u6839\u64da\u4e0d\u540c\u7684\u9700\u6c42\u548c\u4f7f\u7528\u5834\u666f\uff0c\u9078\u64c7\u5408\u9069\u7684\u6578\u64da\u5eab\u985e\u578b\u81f3\u95dc\u91cd\u8981\u3002\u672c\u6587\u5c07\u63a2\u8a0e\u201c\u7a7a\u683c\u201d\u9019\u4e00\u8853\u8a9e\u5728\u6578\u64da\u5eab\u4e2d\u7684\u542b\u7fa9\uff0c\u4ee5\u53ca\u5b83\u6240\u5c6c\u7684\u6578\u64da\u5eab\u985e\u578b\u3002<\/p>\n

\u4ec0\u9ebc\u662f\u7a7a\u683c\uff1f<\/h2>\n

\u5728\u6578\u64da\u5eab\u4e2d\uff0c\u201c\u7a7a\u683c\u201d\u901a\u5e38\u6307\u7684\u662f\u4e00\u7a2e\u6578\u64da\u7d50\u69cb\u6216\u6578\u64da\u985e\u578b\uff0c\u7528\u65bc\u8868\u793a\u7a7a\u503c\u6216\u7f3a\u5931\u503c\u3002\u9019\u5728\u6578\u64da\u5eab\u8a2d\u8a08\u4e2d\u662f\u975e\u5e38\u91cd\u8981\u7684\uff0c\u56e0\u70ba\u5b83\u80fd\u5920\u5e6b\u52a9\u958b\u767c\u8005\u548c\u6578\u64da\u5206\u6790\u5e2b\u7406\u89e3\u6578\u64da\u7684\u5b8c\u6574\u6027\u548c\u6e96\u78ba\u6027\u3002<\/p>\n

\u7a7a\u683c\u7684\u6578\u64da\u5eab\u985e\u578b<\/h2>\n

\u6839\u64da\u6578\u64da\u5eab\u7684\u8a2d\u8a08\u548c\u4f7f\u7528\u65b9\u5f0f\uff0c\u7a7a\u683c\u53ef\u4ee5\u51fa\u73fe\u5728\u591a\u7a2e\u6578\u64da\u5eab\u985e\u578b\u4e2d\u3002\u4ee5\u4e0b\u662f\u5e7e\u7a2e\u5e38\u898b\u7684\u6578\u64da\u5eab\u985e\u578b\u53ca\u5176\u5c0d\u7a7a\u683c\u7684\u8655\u7406\u65b9\u5f0f\uff1a<\/p>\n

1. \u95dc\u4fc2\u578b\u6578\u64da\u5eab<\/h3>\n

\u95dc\u4fc2\u578b\u6578\u64da\u5eab\uff08\u5982 MySQL\u3001PostgreSQL \u548c Oracle\uff09\u4f7f\u7528\u8868\u683c\u4f86\u5b58\u5132\u6578\u64da\u3002\u5728\u9019\u4e9b\u6578\u64da\u5eab\u4e2d\uff0c\u7a7a\u683c\u901a\u5e38\u8868\u793a\u67d0\u500b\u5b57\u6bb5\u7684\u503c\u70ba NULL\u3002NULL \u503c\u5728 SQL \u4e2d\u5177\u6709\u7279\u6b8a\u7684\u610f\u7fa9\uff0c\u8868\u793a\u8a72\u5b57\u6bb5\u6c92\u6709\u503c\u6216\u672a\u77e5\u503c\u3002\u4f8b\u5982\uff1a<\/p>\n

SELECT * FROM users WHERE email IS NULL;<\/code><\/pre>\n
\u9019\u689d\u67e5\u8a62\u5c07\u8fd4\u56de\u6240\u6709\u96fb\u5b50\u90f5\u4ef6\u5730\u5740\u70ba\u7a7a\u7684\u7528\u6236\u3002<\/p>\n
2. \u975e\u95dc\u4fc2\u578b\u6578\u64da\u5eab<\/h3>\n
\u975e\u95dc\u4fc2\u578b\u6578\u64da\u5eab\uff08\u5982 MongoDB \u548c Cassandra\uff09\u5247\u4f7f\u7528\u4e0d\u540c\u7684\u6578\u64da\u7d50\u69cb\u4f86\u5b58\u5132\u6578\u64da\u3002\u5728\u9019\u4e9b\u6578\u64da\u5eab\u4e2d\uff0c\u7a7a\u683c\u7684\u8655\u7406\u65b9\u5f0f\u53ef\u80fd\u6703\u6709\u6240\u4e0d\u540c\u3002\u4f8b\u5982\uff0c\u5728 MongoDB \u4e2d\uff0c\u6587\u6a94\u4e2d\u7684\u67d0\u500b\u5b57\u6bb5\u5982\u679c\u4e0d\u5b58\u5728\uff0c\u5247\u8a72\u5b57\u6bb5\u7684\u503c\u88ab\u8996\u70ba\u7a7a\u3002\u9019\u610f\u5473\u8457\u5728\u67e5\u8a62\u6642\uff0c\u958b\u767c\u8005\u9700\u8981\u7279\u5225\u6ce8\u610f\u5b57\u6bb5\u7684\u5b58\u5728\u6027\u3002<\/p>\n
db.users.find({ email: { $exists: false } });<\/code><\/pre>\n
\u9019\u689d\u67e5\u8a62\u5c07\u8fd4\u56de\u6240\u6709\u96fb\u5b50\u90f5\u4ef6\u5b57\u6bb5\u4e0d\u5b58\u5728\u7684\u7528\u6236\u3002<\/p>\n
3. \u6642\u5e8f\u6578\u64da\u5eab<\/h3>\n
\u6642\u5e8f\u6578\u64da\u5eab\uff08\u5982 InfluxDB \u548c TimescaleDB\uff09\u5c08\u9580\u7528\u65bc\u8655\u7406\u6642\u9593\u5e8f\u5217\u6578\u64da\u3002\u5728\u9019\u4e9b\u6578\u64da\u5eab\u4e2d\uff0c\u7a7a\u683c\u53ef\u80fd\u8868\u793a\u67d0\u500b\u6642\u9593\u9ede\u7684\u6578\u64da\u7f3a\u5931\u3002\u4f8b\u5982\uff0c\u5728\u8a18\u9304\u6eab\u5ea6\u6578\u64da\u6642\uff0c\u5982\u679c\u67d0\u500b\u6642\u9593\u9ede\u6c92\u6709\u6578\u64da\uff0c\u5247\u8a72\u6642\u9593\u9ede\u7684\u503c\u53ef\u4ee5\u8a2d\u7f6e\u70ba NULL \u6216\u7a7a\u683c\u3002<\/p>\n
SELECT * FROM temperature WHERE value IS NULL;<\/code><\/pre>\n
\u9019\u689d\u67e5\u8a62\u5c07\u8fd4\u56de\u6240\u6709\u6eab\u5ea6\u503c\u70ba\u7a7a\u7684\u8a18\u9304\u3002<\/p>\n
\u7a7a\u683c\u7684\u5f71\u97ff<\/h2>\n
\u5728\u6578\u64da\u5eab\u4e2d\u4f7f\u7528\u7a7a\u683c\u6216 NULL \u503c\u6703\u5c0d\u6578\u64da\u7684\u5b8c\u6574\u6027\u548c\u67e5\u8a62\u6027\u80fd\u7522\u751f\u5f71\u97ff\u3002\u904e\u591a\u7684\u7a7a\u683c\u53ef\u80fd\u6703\u5c0e\u81f4\u6578\u64da\u5206\u6790\u6642\u7684\u56f0\u96e3\uff0c\u56e0\u70ba\u5728\u9032\u884c\u7d71\u8a08\u8a08\u7b97\u6642\uff0cNULL \u503c\u901a\u5e38\u6703\u88ab\u5ffd\u7565\u3002\u6b64\u5916\uff0c\u5c0d\u65bc\u67d0\u4e9b\u67e5\u8a62\uff0cNULL \u503c\u7684\u5b58\u5728\u53ef\u80fd\u6703\u5f71\u97ff\u67e5\u8a62\u7684\u7d50\u679c\u96c6\u3002<\/p>\n
\u7d50\u8ad6<\/h2>\n
\u7a7a\u683c\u5728\u6578\u64da\u5eab\u4e2d\u662f\u4e00\u500b\u91cd\u8981\u7684\u6982\u5ff5\uff0c\u7121\u8ad6\u662f\u5728\u95dc\u4fc2\u578b\u6578\u64da\u5eab\u9084\u662f\u975e\u95dc\u4fc2\u578b\u6578\u64da\u5eab\u4e2d\uff0c\u6b63\u78ba\u7406\u89e3\u548c\u8655\u7406\u7a7a\u683c\u5c0d\u65bc\u6578\u64da\u7684\u6e96\u78ba\u6027\u548c\u5b8c\u6574\u6027\u81f3\u95dc\u91cd\u8981\u3002\u9078\u64c7\u5408\u9069\u7684\u6578\u64da\u5eab\u985e\u578b\u548c\u8a2d\u8a08\u6578\u64da\u7d50\u69cb\u6642\uff0c\u958b\u767c\u8005\u61c9\u8a72\u8003\u616e\u5982\u4f55\u6709\u6548\u5730\u7ba1\u7406\u7a7a\u683c\uff0c\u4ee5\u78ba\u4fdd\u6578\u64da\u7684\u8cea\u91cf\u548c\u53ef\u7528\u6027\u3002<\/p>\n
\u5982\u679c\u60a8\u5c0d\u65bc\u9078\u64c7\u5408\u9069\u7684\u6578\u64da\u5eab\u985e\u578b\u6216\u9700\u8981\u66f4\u591a\u6709\u95dc \u9999\u6e2fVPS<\/a> \u7684\u8cc7\u8a0a\uff0c\u8acb\u96a8\u6642\u8a2a\u554f\u6211\u5011\u7684\u7db2\u7ad9\u4ee5\u7372\u53d6\u66f4\u591a\u5e6b\u52a9\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u7a7a\u683c\u662f\u4e00\u7a2e\u95dc\u4fc2\u578b\u6578\u64da\u5eab\uff0c\u5c08\u6ce8\u65bc\u7d50\u69cb\u5316\u6578\u64da\u7684\u5b58\u5132\u548c\u7ba1\u7406\uff0c\u652f\u6301SQL\u67e5\u8a62\u548c\u6578\u64da\u5b8c\u6574\u6027\u3002<\/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-165365","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/165365","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=165365"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/165365\/revisions"}],"predecessor-version":[{"id":165366,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/165365\/revisions\/165366"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=165365"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=165365"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=165365"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}