{"id":143957,"date":"2024-11-01T02:40:18","date_gmt":"2024-10-31T18:40:18","guid":{"rendered":"https:\/\/server.hk\/cnblog\/143957\/"},"modified":"2024-11-01T02:40:19","modified_gmt":"2024-10-31T18:40:19","slug":"sql-%e6%95%b8%e6%93%9a%e5%ba%ab%e7%9a%84%e9%99%a4%e6%b3%95%e9%81%8b%e7%ae%97%e6%96%b9%e6%b3%95%e8%a9%b3%e8%a7%a3-sql-%e6%95%b8%e6%93%9a%e5%ba%ab%e9%99%a4%e6%b3%95%e8%aa%9e%e5%8f%a5","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/143957\/","title":{"rendered":"SQL \u6578\u64da\u5eab\u7684\u9664\u6cd5\u904b\u7b97\u65b9\u6cd5\u8a73\u89e3 (sql \u6578\u64da\u5eab\u9664\u6cd5\u8a9e\u53e5)"},"content":{"rendered":"

SQL \u6578\u64da\u5eab\u7684\u9664\u6cd5\u904b\u7b97\u65b9\u6cd5\u8a73\u89e3<\/h1>\n

\u5728 SQL \u6578\u64da\u5eab\u4e2d\uff0c\u9664\u6cd5\u904b\u7b97\u662f\u4e00\u500b\u5e38\u898b\u7684\u9700\u6c42\uff0c\u5c24\u5176\u662f\u5728\u8655\u7406\u6578\u64da\u5206\u6790\u548c\u5831\u544a\u6642\u3002\u672c\u6587\u5c07\u6df1\u5165\u63a2\u8a0e SQL \u6578\u64da\u5eab\u4e2d\u7684\u9664\u6cd5\u904b\u7b97\u65b9\u6cd5\uff0c\u4e26\u63d0\u4f9b\u76f8\u95dc\u7684\u8a9e\u53e5\u548c\u793a\u4f8b\uff0c\u4ee5\u5e6b\u52a9\u8b80\u8005\u66f4\u597d\u5730\u7406\u89e3\u5982\u4f55\u5728 SQL \u4e2d\u9032\u884c\u9664\u6cd5\u904b\u7b97\u3002<\/p>\n

\u9664\u6cd5\u904b\u7b97\u7684\u57fa\u672c\u6982\u5ff5<\/h2>\n

\u5728\u6578\u5b78\u4e2d\uff0c\u9664\u6cd5\u904b\u7b97\u662f\u5c07\u4e00\u500b\u6578\u5b57\u5206\u6210\u82e5\u5e72\u7b49\u4efd\u7684\u904e\u7a0b\u3002\u5728 SQL \u4e2d\uff0c\u9664\u6cd5\u904b\u7b97\u901a\u5e38\u7528\u65bc\u8a08\u7b97\u6bd4\u7387\u3001\u5e73\u5747\u503c\u6216\u5176\u4ed6\u9700\u8981\u5c07\u4e00\u500b\u6578\u5b57\u9664\u4ee5\u53e6\u4e00\u500b\u6578\u5b57\u7684\u60c5\u6cc1\u3002SQL \u4e2d\u7684\u9664\u6cd5\u904b\u7b97\u7b26\u70ba \/<\/code>\u3002<\/p>\n

\u57fa\u672c\u7684\u9664\u6cd5\u8a9e\u53e5<\/h2>\n

\u5728 SQL \u4e2d\uff0c\u9032\u884c\u9664\u6cd5\u904b\u7b97\u7684\u57fa\u672c\u8a9e\u6cd5\u5982\u4e0b\uff1a<\/p>\n

SELECT column1, column2, (column1 \/ column2) AS result\nFROM table_name;\n<\/code><\/pre>\n
\u5728\u9019\u500b\u8a9e\u53e5\u4e2d\uff0ccolumn1<\/code> \u548c column2<\/code> \u662f\u9700\u8981\u9032\u884c\u9664\u6cd5\u904b\u7b97\u7684\u5217\uff0cresult<\/code> \u662f\u904b\u7b97\u7d50\u679c\u7684\u5225\u540d\uff0ctable_name<\/code> \u662f\u6578\u64da\u8868\u7684\u540d\u7a31\u3002<\/p>\n
\u793a\u4f8b\uff1a\u8a08\u7b97\u5e73\u5747\u5206\u6578<\/h2>\n
\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70ba students<\/code> \u7684\u8868\uff0c\u8a72\u8868\u5305\u542b\u5b78\u751f\u7684\u59d3\u540d\u548c\u4ed6\u5011\u7684\u7e3d\u5206\u6578\u4ee5\u53ca\u79d1\u76ee\u6578\u91cf\u3002\u6211\u5011\u5e0c\u671b\u8a08\u7b97\u6bcf\u4f4d\u5b78\u751f\u7684\u5e73\u5747\u5206\u6578\u3002\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b SQL \u8a9e\u53e5\uff1a<\/p>\n
SELECT name, total_score, subjects, (total_score \/ subjects) AS average_score\nFROM students;\n<\/code><\/pre>\n
\u5728\u9019\u500b\u4f8b\u5b50\u4e2d\uff0ctotal_score<\/code> \u662f\u5b78\u751f\u7684\u7e3d\u5206\u6578\uff0csubjects<\/code> \u662f\u5b78\u751f\u6240\u4fee\u7684\u79d1\u76ee\u6578\u91cf\uff0caverage_score<\/code> \u662f\u8a08\u7b97\u51fa\u4f86\u7684\u5e73\u5747\u5206\u6578\u3002<\/p>\n
\u8655\u7406\u9664\u4ee5\u96f6\u7684\u60c5\u6cc1<\/h2>\n
\u5728\u9032\u884c\u9664\u6cd5\u904b\u7b97\u6642\uff0c\u6700\u5e38\u898b\u7684\u932f\u8aa4\u4e4b\u4e00\u662f\u9664\u4ee5\u96f6\u3002\u9019\u6703\u5c0e\u81f4 SQL \u932f\u8aa4\uff0c\u56e0\u6b64\u5728\u9032\u884c\u9664\u6cd5\u904b\u7b97\u6642\uff0c\u61c9\u8a72\u7279\u5225\u6ce8\u610f\u9019\u4e00\u9ede\u3002\u53ef\u4ee5\u4f7f\u7528 CASE<\/code> \u8a9e\u53e5\u4f86\u907f\u514d\u9019\u7a2e\u60c5\u6cc1\uff1a<\/p>\n
SELECT name, total_score, subjects,\n       CASE \n           WHEN subjects = 0 THEN 'N\/A'\n           ELSE (total_score \/ subjects)\n       END AS average_score\nFROM students;\n<\/code><\/pre>\n
\u5728\u9019\u500b\u4f8b\u5b50\u4e2d\uff0c\u7576 subjects<\/code> \u70ba\u96f6\u6642\uff0c\u5c07\u8fd4\u56de ‘N\/A’\uff0c\u5426\u5247\u5c07\u8a08\u7b97\u5e73\u5747\u5206\u6578\u3002<\/p>\n
\u4f7f\u7528\u805a\u5408\u51fd\u6578\u9032\u884c\u9664\u6cd5\u904b\u7b97<\/h2>\n
\u5728\u67d0\u4e9b\u60c5\u6cc1\u4e0b\uff0c\u6211\u5011\u53ef\u80fd\u9700\u8981\u5c0d\u6574\u500b\u6578\u64da\u96c6\u9032\u884c\u9664\u6cd5\u904b\u7b97\uff0c\u4f8b\u5982\u8a08\u7b97\u6240\u6709\u5b78\u751f\u7684\u7e3d\u5206\u6578\u8207\u7e3d\u79d1\u76ee\u6578\u7684\u6bd4\u7387\u3002\u53ef\u4ee5\u4f7f\u7528\u805a\u5408\u51fd\u6578\u4f86\u5be6\u73fe\uff1a<\/p>\n
SELECT SUM(total_score) AS total_score, SUM(subjects) AS total_subjects,\n       (SUM(total_score) \/ SUM(subjects)) AS overall_average\nFROM students;\n<\/code><\/pre>\n
\u9019\u500b\u8a9e\u53e5\u5c07\u8a08\u7b97\u6240\u6709\u5b78\u751f\u7684\u7e3d\u5206\u6578\u548c\u7e3d\u79d1\u76ee\u6578\uff0c\u4e26\u8fd4\u56de\u6574\u9ad4\u7684\u5e73\u5747\u5206\u6578\u3002<\/p>\n
\u7d50\u8ad6<\/h2>\n
\u5728 SQL \u6578\u64da\u5eab\u4e2d\uff0c\u9664\u6cd5\u904b\u7b97\u662f\u4e00\u500b\u91cd\u8981\u7684\u529f\u80fd\uff0c\u80fd\u5920\u5e6b\u52a9\u7528\u6236\u9032\u884c\u6578\u64da\u5206\u6790\u548c\u5831\u544a\u3002\u901a\u904e\u6b63\u78ba\u4f7f\u7528\u9664\u6cd5\u904b\u7b97\u7b26\u548c\u8655\u7406\u9664\u4ee5\u96f6\u7684\u60c5\u6cc1\uff0c\u7528\u6236\u53ef\u4ee5\u6709\u6548\u5730\u8a08\u7b97\u6240\u9700\u7684\u6578\u64da\u3002\u5e0c\u671b\u672c\u6587\u80fd\u5920\u5e6b\u52a9\u8b80\u8005\u66f4\u597d\u5730\u7406\u89e3 SQL \u4e2d\u7684\u9664\u6cd5\u904b\u7b97\u65b9\u6cd5\u3002<\/p>\n
\u5982\u679c\u60a8\u5c0d\u65bc VPS<\/a> \u670d\u52d9\u6216\u5176\u4ed6\u76f8\u95dc\u6280\u8853\u6709\u8208\u8da3\uff0c\u6b61\u8fce\u8a2a\u554f\u6211\u5011\u7684\u7db2\u7ad9\u4ee5\u7372\u53d6\u66f4\u591a\u8cc7\u8a0a\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u6df1\u5165\u63a2\u8a0e SQL \u6578\u64da\u5eab\u4e2d\u7684\u9664\u6cd5\u904b\u7b97\u65b9\u6cd5\uff0c\u63d0\u4f9b\u8a73\u7d30\u8a9e\u53e5\u7bc4\u4f8b\u8207\u61c9\u7528\u6280\u5de7\uff0c\u52a9\u4f60\u8f15\u9b06\u638c\u63e1\u6578\u64da\u8655\u7406\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-143957","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/143957","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=143957"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/143957\/revisions"}],"predecessor-version":[{"id":143958,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/143957\/revisions\/143958"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=143957"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=143957"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=143957"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}