{"id":179776,"date":"2024-11-09T04:42:29","date_gmt":"2024-11-08T20:42:29","guid":{"rendered":"https:\/\/server.hk\/cnblog\/179776\/"},"modified":"2024-11-09T04:42:30","modified_gmt":"2024-11-08T20:42:30","slug":"%e5%a6%82%e4%bd%95%e5%9c%a8%e6%b2%92%e6%9c%89%e5%ba%8f%e5%88%97%e8%99%9f%e7%9a%84%e6%83%85%e6%b3%81%e4%b8%8b%e6%ad%a3%e7%a2%ba%e7%b5%b1%e8%a8%88%e6%95%b8%e6%93%9a%e5%ba%ab%e6%a2%9d%e6%95%b8%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/179776\/","title":{"rendered":"\u5982\u4f55\u5728\u6c92\u6709\u5e8f\u5217\u865f\u7684\u60c5\u6cc1\u4e0b\u6b63\u78ba\u7d71\u8a08\u6578\u64da\u5eab\u689d\u6578\uff1f (\u7121\u5e8f\u5217\u865f\u600e\u9ebc\u7d71\u8a08\u6578\u64da\u5eab\u4e2d\u7684\u689d\u6578)"},"content":{"rendered":"

\u5982\u4f55\u5728\u6c92\u6709\u5e8f\u5217\u865f\u7684\u60c5\u6cc1\u4e0b\u6b63\u78ba\u7d71\u8a08\u6578\u64da\u5eab\u689d\u6578\uff1f<\/h1>\n

\u5728\u6578\u64da\u5eab\u7ba1\u7406\u4e2d\uff0c\u7d71\u8a08\u6578\u64da\u5eab\u4e2d\u7684\u689d\u6578\u662f\u4e00\u500b\u5e38\u898b\u7684\u9700\u6c42\u3002\u901a\u5e38\uff0c\u9019\u53ef\u4ee5\u901a\u904e\u4f7f\u7528\u5e8f\u5217\u865f\u6216\u4e3b\u9375\u4f86\u8f15\u9b06\u5be6\u73fe\u3002\u7136\u800c\uff0c\u7576\u6578\u64da\u5eab\u4e2d\u6c92\u6709\u5e8f\u5217\u865f\u6216\u4e3b\u9375\u6642\uff0c\u5982\u4f55\u6b63\u78ba\u5730\u7d71\u8a08\u689d\u6578\u5462\uff1f\u672c\u6587\u5c07\u63a2\u8a0e\u5e7e\u7a2e\u65b9\u6cd5\u4f86\u89e3\u6c7a\u9019\u4e00\u554f\u984c\u3002<\/p>\n

1. \u4f7f\u7528 COUNT \u51fd\u6578<\/h2>\n

\u6700\u57fa\u672c\u7684\u65b9\u6cd5\u662f\u4f7f\u7528 SQL \u7684 COUNT<\/code> \u51fd\u6578\u3002\u9019\u500b\u51fd\u6578\u53ef\u4ee5\u7528\u4f86\u8a08\u7b97\u8868\u4e2d\u884c\u7684\u6578\u91cf\u3002\u5373\u4f7f\u6c92\u6709\u5e8f\u5217\u865f\uff0c\u9019\u500b\u65b9\u6cd5\u4f9d\u7136\u6709\u6548\u3002<\/p>\n

SELECT COUNT(*) FROM your_table_name;<\/code><\/pre>\n
\u9019\u689d SQL \u8a9e\u53e5\u5c07\u8fd4\u56de\u8868 your_table_name<\/code> \u4e2d\u7684\u6240\u6709\u884c\u6578\u3002\u9019\u662f\u6700\u76f4\u63a5\u4e14\u9ad8\u6548\u7684\u65b9\u5f0f\uff0c\u9069\u7528\u65bc\u5927\u591a\u6578\u60c5\u6cc1\u3002<\/p>\n
2. \u4f7f\u7528 GROUP BY \u548c HAVING<\/h2>\n
\u5728\u67d0\u4e9b\u60c5\u6cc1\u4e0b\uff0c\u60a8\u53ef\u80fd\u9700\u8981\u6839\u64da\u7279\u5b9a\u689d\u4ef6\u4f86\u7d71\u8a08\u6578\u64da\u3002\u4f8b\u5982\uff0c\u60a8\u53ef\u80fd\u5e0c\u671b\u7d71\u8a08\u67d0\u500b\u5b57\u6bb5\u7684\u552f\u4e00\u503c\u6578\u91cf\u3002\u9019\u6642\u53ef\u4ee5\u4f7f\u7528 GROUP BY<\/code> \u548c HAVING<\/code> \u5b50\u53e5\u3002<\/p>\n
SELECT column_name, COUNT(*) \nFROM your_table_name \nGROUP BY column_name \nHAVING COUNT(*) > 1;<\/code><\/pre>\n
\u9019\u689d\u8a9e\u53e5\u5c07\u8fd4\u56de\u5728 your_table_name<\/code> \u4e2d\uff0c\u67d0\u500b\u5b57\u6bb5 column_name<\/code> \u7684\u6240\u6709\u91cd\u8907\u503c\u53ca\u5176\u51fa\u73fe\u6b21\u6578\u3002<\/p>\n
3. \u4f7f\u7528 DISTINCT<\/h2>\n
\u5982\u679c\u60a8\u53ea\u60f3\u8a08\u7b97\u67d0\u500b\u5b57\u6bb5\u7684\u552f\u4e00\u503c\u6578\u91cf\uff0c\u53ef\u4ee5\u4f7f\u7528 DISTINCT<\/code> \u95dc\u9375\u5b57\u3002<\/p>\n
SELECT COUNT(DISTINCT column_name) FROM your_table_name;<\/code><\/pre>\n
\u9019\u689d\u8a9e\u53e5\u5c07\u8fd4\u56de your_table_name<\/code> \u4e2d column_name<\/code> \u7684\u552f\u4e00\u503c\u6578\u91cf\uff0c\u9019\u5728\u6c92\u6709\u5e8f\u5217\u865f\u7684\u60c5\u6cc1\u4e0b\u4e5f\u80fd\u6709\u6548\u5730\u63d0\u4f9b\u6240\u9700\u7684\u7d71\u8a08\u6578\u64da\u3002<\/p>\n
4. \u4f7f\u7528\u7d22\u5f15<\/h2>\n
\u5982\u679c\u60a8\u7684\u6578\u64da\u5eab\u8868\u4e2d\u6709\u7d22\u5f15\uff0c\u5373\u4f7f\u6c92\u6709\u5e8f\u5217\u865f\uff0c\u60a8\u4e5f\u53ef\u4ee5\u5229\u7528\u7d22\u5f15\u4f86\u52a0\u901f\u67e5\u8a62\u3002\u7d22\u5f15\u53ef\u4ee5\u63d0\u9ad8\u67e5\u8a62\u6027\u80fd\uff0c\u7279\u5225\u662f\u5728\u5927\u578b\u6578\u64da\u96c6\u4e0a\u9032\u884c\u7d71\u8a08\u6642\u3002<\/p>\n
\u4f8b\u5982\uff0c\u60a8\u53ef\u4ee5\u5728\u67d0\u500b\u5b57\u6bb5\u4e0a\u5275\u5efa\u7d22\u5f15\uff0c\u7136\u5f8c\u4f7f\u7528 COUNT<\/code> \u51fd\u6578\u4f86\u7d71\u8a08\u689d\u6578\uff1a<\/p>\n
CREATE INDEX idx_column_name ON your_table_name(column_name);<\/code><\/pre>\n
\u9019\u6a23\u53ef\u4ee5\u63d0\u9ad8\u5f8c\u7e8c\u67e5\u8a62\u7684\u6548\u7387\u3002<\/p>\n
5. \u4f7f\u7528\u81e8\u6642\u8868<\/h2>\n
\u5728\u67d0\u4e9b\u60c5\u6cc1\u4e0b\uff0c\u60a8\u53ef\u80fd\u9700\u8981\u9032\u884c\u66f4\u8907\u96dc\u7684\u7d71\u8a08\u3002\u9019\u6642\u53ef\u4ee5\u8003\u616e\u4f7f\u7528\u81e8\u6642\u8868\u4f86\u5b58\u5132\u4e2d\u9593\u7d50\u679c\uff0c\u7136\u5f8c\u518d\u9032\u884c\u7d71\u8a08\u3002<\/p>\n
CREATE TEMPORARY TABLE temp_table AS \nSELECT column_name FROM your_table_name;\n\nSELECT COUNT(*) FROM temp_table;<\/code><\/pre>\n
\u9019\u6a23\u53ef\u4ee5\u5728\u4e0d\u5f71\u97ff\u539f\u59cb\u6578\u64da\u7684\u60c5\u6cc1\u4e0b\u9032\u884c\u7d71\u8a08\u3002<\/p>\n
\u7e3d\u7d50<\/h2>\n
\u5728\u6c92\u6709\u5e8f\u5217\u865f\u7684\u60c5\u6cc1\u4e0b\uff0c\u7d71\u8a08\u6578\u64da\u5eab\u4e2d\u7684\u689d\u6578\u4ecd\u7136\u662f\u53ef\u884c\u7684\uff0c\u4e26\u4e14\u6709\u591a\u7a2e\u65b9\u6cd5\u53ef\u4ee5\u5be6\u73fe\u3002\u7121\u8ad6\u662f\u4f7f\u7528 COUNT<\/code> \u51fd\u6578\u3001GROUP BY<\/code>\u3001DISTINCT<\/code> \u9084\u662f\u5229\u7528\u7d22\u5f15\u548c\u81e8\u6642\u8868\uff0c\u9019\u4e9b\u65b9\u6cd5\u90fd\u80fd\u6709\u6548\u5730\u5e6b\u52a9\u60a8\u7372\u5f97\u6240\u9700\u7684\u6578\u64da\u7d71\u8a08\u3002<\/p>\n
\u5982\u679c\u60a8\u6b63\u5728\u5c0b\u627e\u9ad8\u6548\u7684\u6578\u64da\u5eab\u89e3\u6c7a\u65b9\u6848\uff0c\u8003\u616e\u4f7f\u7528 \u9999\u6e2fVPS<\/a> \u670d\u52d9\u4f86\u63d0\u5347\u60a8\u7684\u6578\u64da\u8655\u7406\u80fd\u529b\u3002\u7121\u8ad6\u662f\u6578\u64da\u5eab\u7ba1\u7406\u9084\u662f\u5176\u4ed6\u61c9\u7528\uff0c\u9999\u6e2f\u4f3a\u670d\u5668<\/a> \u90fd\u80fd\u70ba\u60a8\u63d0\u4f9b\u7a69\u5b9a\u7684\u652f\u6301\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u5b78\u7fd2\u5982\u4f55\u5728\u6c92\u6709\u5e8f\u5217\u865f\u7684\u60c5\u6cc1\u4e0b\uff0c\u6b63\u78ba\u7d71\u8a08\u6578\u64da\u5eab\u4e2d\u7684\u689d\u6578\uff0c\u638c\u63e1\u6709\u6548\u7684\u6578\u64da\u67e5\u8a62\u6280\u5de7\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-179776","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/179776","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=179776"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/179776\/revisions"}],"predecessor-version":[{"id":179777,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/179776\/revisions\/179777"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=179776"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=179776"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=179776"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}