{"id":172825,"date":"2024-11-07T15:22:19","date_gmt":"2024-11-07T07:22:19","guid":{"rendered":"https:\/\/server.hk\/cnblog\/172825\/"},"modified":"2024-11-07T15:22:20","modified_gmt":"2024-11-07T07:22:20","slug":"%e5%a6%82%e4%bd%95%e6%9f%a5%e8%a9%a2%e6%95%b8%e6%93%9a%e5%ba%ab%e4%b8%ad%e5%94%af%e4%b8%80%e7%9a%84%e5%88%97%ef%bc%9f-%e6%9f%a5%e8%a9%a2%e6%95%b8%e6%93%9a%e5%ba%ab%e4%b8%ad%e4%b8%8d%e9%87%8d%e8%a4%87","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/172825\/","title":{"rendered":"\u5982\u4f55\u67e5\u8a62\u6578\u64da\u5eab\u4e2d\u552f\u4e00\u7684\u5217\uff1f (\u67e5\u8a62\u6578\u64da\u5eab\u4e2d\u4e0d\u91cd\u8907\u7684\u5217)"},"content":{"rendered":"

\u5982\u4f55\u67e5\u8a62\u6578\u64da\u5eab\u4e2d\u552f\u4e00\u7684\u5217\uff1f (\u67e5\u8a62\u6578\u64da\u5eab\u4e2d\u4e0d\u91cd\u8907\u7684\u5217)<\/h1>\n

\u5728\u6578\u64da\u5eab\u7ba1\u7406\u4e2d\uff0c\u67e5\u8a62\u4e0d\u91cd\u8907\u7684\u5217\u662f\u4e00\u500b\u5e38\u898b\u7684\u9700\u6c42\u3002\u9019\u4e0d\u50c5\u6709\u52a9\u65bc\u6578\u64da\u7684\u6e05\u7406\uff0c\u9084\u80fd\u63d0\u9ad8\u67e5\u8a62\u7684\u6548\u7387\u3002\u672c\u6587\u5c07\u4ecb\u7d39\u5982\u4f55\u5728\u4e0d\u540c\u7684\u6578\u64da\u5eab\u7cfb\u7d71\u4e2d\u67e5\u8a62\u552f\u4e00\u7684\u5217\uff0c\u4e26\u63d0\u4f9b\u76f8\u61c9\u7684\u793a\u4f8b\u548c\u4ee3\u78bc\u7247\u6bb5\u3002<\/p>\n

\u4ec0\u9ebc\u662f\u552f\u4e00\u7684\u5217\uff1f<\/h2>\n

\u552f\u4e00\u7684\u5217\u662f\u6307\u5728\u6578\u64da\u5eab\u8868\u4e2d\uff0c\u6bcf\u4e00\u884c\u7684\u8a72\u5217\u503c\u90fd\u662f\u4e0d\u91cd\u8907\u7684\u3002\u9019\u901a\u5e38\u7528\u65bc\u6a19\u8b58\u6bcf\u4e00\u689d\u8a18\u9304\uff0c\u4f8b\u5982\u7528\u6236ID\u6216\u7522\u54c1\u7de8\u865f\u3002\u78ba\u4fdd\u67d0\u4e00\u5217\u7684\u552f\u4e00\u6027\u53ef\u4ee5\u9632\u6b62\u6578\u64da\u91cd\u8907\uff0c\u5f9e\u800c\u63d0\u9ad8\u6578\u64da\u7684\u5b8c\u6574\u6027\u3002<\/p>\n

\u67e5\u8a62\u552f\u4e00\u5217\u7684\u65b9\u6cd5<\/h2>\n

\u5728\u4e0d\u540c\u7684\u6578\u64da\u5eab\u7cfb\u7d71\u4e2d\uff0c\u67e5\u8a62\u552f\u4e00\u5217\u7684\u65b9\u6cd5\u53ef\u80fd\u6703\u6709\u6240\u4e0d\u540c\u3002\u4ee5\u4e0b\u662f\u4e00\u4e9b\u5e38\u898b\u7684\u6578\u64da\u5eab\u7cfb\u7d71\u53ca\u5176\u67e5\u8a62\u65b9\u6cd5\uff1a<\/p>\n

1. MySQL<\/h3>\n

\u5728MySQL\u4e2d\uff0c\u53ef\u4ee5\u4f7f\u7528SELECT DISTINCT<\/strong>\u8a9e\u53e5\u4f86\u67e5\u8a62\u4e0d\u91cd\u8907\u7684\u5217\u3002\u4ee5\u4e0b\u662f\u4e00\u500b\u793a\u4f8b\uff1a<\/p>\n

SELECT DISTINCT column_name FROM table_name;<\/code><\/pre>\n
\u9019\u689d\u8a9e\u53e5\u5c07\u8fd4\u56de\u6307\u5b9a\u5217\u4e2d\u6240\u6709\u4e0d\u91cd\u8907\u7684\u503c\u3002\u4f8b\u5982\uff0c\u5982\u679c\u6211\u5011\u6709\u4e00\u500b\u540d\u70bausers<\/strong>\u7684\u8868\uff0c\u4e26\u5e0c\u671b\u67e5\u8a62\u6240\u6709\u4e0d\u91cd\u8907\u7684\u7528\u6236\u540d\uff0c\u53ef\u4ee5\u9019\u6a23\u5beb\uff1a<\/p>\n
SELECT DISTINCT username FROM users;<\/code><\/pre>\n
2. PostgreSQL<\/h3>\n
\u5728PostgreSQL\u4e2d\uff0c\u67e5\u8a62\u552f\u4e00\u5217\u7684\u65b9\u6cd5\u8207MySQL\u985e\u4f3c\uff0c\u540c\u6a23\u4f7f\u7528SELECT DISTINCT<\/strong>\u8a9e\u53e5\uff1a<\/p>\n
SELECT DISTINCT column_name FROM table_name;<\/code><\/pre>\n
\u4f8b\u5982\uff0c\u67e5\u8a62\u4e0d\u91cd\u8907\u7684\u96fb\u5b50\u90f5\u4ef6\u5730\u5740\uff1a<\/p>\n
SELECT DISTINCT email FROM users;<\/code><\/pre>\n
3. SQL Server<\/h3>\n
\u5728SQL Server\u4e2d\uff0c\u67e5\u8a62\u552f\u4e00\u5217\u4e5f\u53ef\u4ee5\u4f7f\u7528SELECT DISTINCT<\/strong>\u8a9e\u53e5\uff0c\u6216\u8005\u4f7f\u7528GROUP BY<\/strong>\u8a9e\u53e5\u4f86\u9054\u5230\u76f8\u540c\u7684\u6548\u679c\uff1a<\/p>\n
SELECT column_name FROM table_name GROUP BY column_name;<\/code><\/pre>\n
\u4f8b\u5982\uff0c\u67e5\u8a62\u4e0d\u91cd\u8907\u7684\u57ce\u5e02\u540d\u7a31\uff1a<\/p>\n
SELECT city FROM users GROUP BY city;<\/code><\/pre>\n
4. Oracle<\/h3>\n
\u5728Oracle\u6578\u64da\u5eab\u4e2d\uff0c\u540c\u6a23\u53ef\u4ee5\u4f7f\u7528SELECT DISTINCT<\/strong>\u8a9e\u53e5\u4f86\u67e5\u8a62\u552f\u4e00\u5217\uff1a<\/p>\n
SELECT DISTINCT column_name FROM table_name;<\/code><\/pre>\n
\u4f8b\u5982\uff0c\u67e5\u8a62\u4e0d\u91cd\u8907\u7684\u570b\u5bb6\u540d\u7a31\uff1a<\/p>\n
SELECT DISTINCT country FROM users;<\/code><\/pre>\n
\u4f7f\u7528\u7d22\u5f15\u4f86\u78ba\u4fdd\u552f\u4e00\u6027<\/h2>\n
\u9664\u4e86\u67e5\u8a62\u4e0d\u91cd\u8907\u7684\u5217\u5916\uff0c\u9084\u53ef\u4ee5\u901a\u904e\u5275\u5efa\u552f\u4e00\u7d22\u5f15\u4f86\u78ba\u4fdd\u67d0\u4e00\u5217\u7684\u552f\u4e00\u6027\u3002\u9019\u6a23\u53ef\u4ee5\u5728\u63d2\u5165\u6578\u64da\u6642\u81ea\u52d5\u6aa2\u67e5\u91cd\u8907\u6027\uff0c\u5f9e\u800c\u63d0\u9ad8\u6578\u64da\u7684\u5b8c\u6574\u6027\u3002<\/p>\n
CREATE UNIQUE INDEX index_name ON table_name (column_name);<\/code><\/pre>\n
\u4f8b\u5982\uff0c\u70ba\u7528\u6236\u8868\u4e2d\u7684\u96fb\u5b50\u90f5\u4ef6\u5730\u5740\u5275\u5efa\u552f\u4e00\u7d22\u5f15\uff1a<\/p>\n
CREATE UNIQUE INDEX idx_email ON users (email);<\/code><\/pre>\n
\u7e3d\u7d50<\/h2>\n
\u67e5\u8a62\u6578\u64da\u5eab\u4e2d\u552f\u4e00\u7684\u5217\u662f\u6578\u64da\u7ba1\u7406\u4e2d\u7684\u4e00\u500b\u91cd\u8981\u4efb\u52d9\u3002\u901a\u904e\u4f7f\u7528SELECT DISTINCT<\/strong>\u8a9e\u53e5\u6216GROUP BY<\/strong>\u8a9e\u53e5\uff0c\u53ef\u4ee5\u8f15\u9b06\u7372\u53d6\u4e0d\u91cd\u8907\u7684\u6578\u64da\u3002\u6b64\u5916\uff0c\u901a\u904e\u5275\u5efa\u552f\u4e00\u7d22\u5f15\uff0c\u53ef\u4ee5\u6709\u6548\u5730\u9632\u6b62\u6578\u64da\u91cd\u8907\uff0c\u78ba\u4fdd\u6578\u64da\u7684\u5b8c\u6574\u6027\u3002\u5c0d\u65bc\u9700\u8981\u9ad8\u6548\u6578\u64da\u8655\u7406\u7684\u7528\u6236\uff0c\u9078\u64c7\u5408\u9069\u7684VPS<\/a><\/strong>\u6216\u9999\u6e2f\u4f3a\u670d\u5668<\/a><\/strong>\u89e3\u6c7a\u65b9\u6848\u5c07\u662f\u660e\u667a\u7684\u9078\u64c7\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u5b78\u7fd2\u5982\u4f55\u5728\u6578\u64da\u5eab\u4e2d\u67e5\u8a62\u552f\u4e00\u5217\uff0c\u7372\u53d6\u4e0d\u91cd\u8907\u7684\u6578\u64da\uff0c\u63d0\u5347\u6578\u64da\u7ba1\u7406\u6548\u7387\uff0c\u7c21\u5316\u67e5\u8a62\u904e\u7a0b\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-172825","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/172825","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=172825"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/172825\/revisions"}],"predecessor-version":[{"id":172826,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/172825\/revisions\/172826"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=172825"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=172825"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=172825"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}