{"id":160649,"date":"2024-11-03T23:51:26","date_gmt":"2024-11-03T15:51:26","guid":{"rendered":"https:\/\/server.hk\/cnblog\/160649\/"},"modified":"2024-11-03T23:51:27","modified_gmt":"2024-11-03T15:51:27","slug":"postgresql%e6%95%99%e7%a8%8bpostgresql-select-%e8%aa%9e%e5%8f%a5","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/160649\/","title":{"rendered":"POSTGRESQL\u6559\u7a0bPostgreSQL SELECT \u8a9e\u53e5"},"content":{"rendered":"

PostgreSQL\u6559\u7a0b\uff1aPostgreSQL SELECT \u8a9e\u53e5<\/h1>\n

PostgreSQL \u662f\u4e00\u7a2e\u5f37\u5927\u7684\u958b\u6e90\u95dc\u806f\u6578\u64da\u5eab\u7ba1\u7406\u7cfb\u7d71\uff0c\u5ee3\u6cdb\u61c9\u7528\u65bc\u5404\u7a2e\u61c9\u7528\u7a0b\u5e8f\u4e2d\u3002\u5176\u9748\u6d3b\u6027\u548c\u64f4\u5c55\u6027\u4f7f\u5176\u6210\u70ba\u958b\u767c\u8005\u548c\u6578\u64da\u79d1\u5b78\u5bb6\u7684\u9996\u9078\u3002\u672c\u6587\u5c07\u6df1\u5165\u63a2\u8a0e PostgreSQL \u4e2d\u7684 SELECT \u8a9e\u53e5\uff0c\u9019\u662f\u7528\u65bc\u67e5\u8a62\u6578\u64da\u7684\u57fa\u672c\u8a9e\u53e5\u4e4b\u4e00\u3002<\/p>\n

SELECT \u8a9e\u53e5\u7684\u57fa\u672c\u7d50\u69cb<\/h2>\n

\u5728 PostgreSQL \u4e2d\uff0cSELECT \u8a9e\u53e5\u7684\u57fa\u672c\u8a9e\u6cd5\u5982\u4e0b\uff1a<\/p>\n

SELECT column1, column2, ...\nFROM table_name\nWHERE condition;<\/code><\/pre>\n
\u9019\u88e1\uff0ccolumn1, column2, ...<\/code> \u662f\u8981\u67e5\u8a62\u7684\u5217\u540d\uff0ctable_name<\/code> \u662f\u6578\u64da\u8868\u7684\u540d\u7a31\uff0c\u800c condition<\/code> \u662f\u53ef\u9078\u7684\u904e\u6ffe\u689d\u4ef6\u3002<\/p>\n
\u57fa\u672c\u67e5\u8a62\u793a\u4f8b<\/h2>\n
\u5047\u8a2d\u6211\u5011\u6709\u4e00\u500b\u540d\u70ba employees<\/code> \u7684\u8868\uff0c\u5305\u542b\u4ee5\u4e0b\u5217\uff1aid<\/code>\u3001name<\/code>\u3001position<\/code> \u548c salary<\/code>\u3002\u6211\u5011\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u8a9e\u53e5\u67e5\u8a62\u6240\u6709\u54e1\u5de5\u7684\u59d3\u540d\u548c\u8077\u4f4d\uff1a<\/p>\n
SELECT name, position\nFROM employees;<\/code><\/pre>\n
\u9019\u5c07\u8fd4\u56de employees<\/code> \u8868\u4e2d\u6240\u6709\u54e1\u5de5\u7684\u59d3\u540d\u548c\u8077\u4f4d\u3002<\/p>\n
\u4f7f\u7528 WHERE \u5b50\u53e5\u904e\u6ffe\u6578\u64da<\/h2>\n
\u5982\u679c\u6211\u5011\u53ea\u60f3\u67e5\u8a62\u85aa\u6c34\u9ad8\u65bc 50000 \u7684\u54e1\u5de5\uff0c\u53ef\u4ee5\u4f7f\u7528 WHERE<\/code> \u5b50\u53e5\u4f86\u904e\u6ffe\u7d50\u679c\uff1a<\/p>\n
SELECT name, position\nFROM employees\nWHERE salary > 50000;<\/code><\/pre>\n
\u9019\u6a23\uff0c\u6211\u5011\u5c31\u80fd\u7372\u5f97\u6240\u6709\u85aa\u6c34\u9ad8\u65bc 50000 \u7684\u54e1\u5de5\u7684\u59d3\u540d\u548c\u8077\u4f4d\u3002<\/p>\n
\u6392\u5e8f\u67e5\u8a62\u7d50\u679c<\/h2>\n
\u5728 PostgreSQL \u4e2d\uff0c\u6211\u5011\u53ef\u4ee5\u4f7f\u7528 ORDER BY<\/code> \u5b50\u53e5\u4f86\u5c0d\u67e5\u8a62\u7d50\u679c\u9032\u884c\u6392\u5e8f\u3002\u4ee5\u4e0b\u793a\u4f8b\u5c07\u6839\u64da\u85aa\u6c34\u5c0d\u54e1\u5de5\u9032\u884c\u964d\u5e8f\u6392\u5e8f\uff1a<\/p>\n
SELECT name, salary\nFROM employees\nORDER BY salary DESC;<\/code><\/pre>\n
\u9019\u5c07\u8fd4\u56de\u6240\u6709\u54e1\u5de5\u7684\u59d3\u540d\u548c\u85aa\u6c34\uff0c\u4e26\u6309\u7167\u85aa\u6c34\u5f9e\u9ad8\u5230\u4f4e\u7684\u9806\u5e8f\u6392\u5217\u3002<\/p>\n
\u4f7f\u7528\u805a\u5408\u51fd\u6578<\/h2>\n
PostgreSQL \u63d0\u4f9b\u4e86\u591a\u7a2e\u805a\u5408\u51fd\u6578\uff0c\u4f8b\u5982 COUNT<\/code>\u3001SUM<\/code>\u3001AVG<\/code>\u3001MAX<\/code> \u548c MIN<\/code>\u3002\u4ee5\u4e0b\u793a\u4f8b\u5c55\u793a\u4e86\u5982\u4f55\u8a08\u7b97\u54e1\u5de5\u7684\u5e73\u5747\u85aa\u6c34\uff1a<\/p>\n
SELECT AVG(salary) AS average_salary\nFROM employees;<\/code><\/pre>\n
\u9019\u5c07\u8fd4\u56de\u6240\u6709\u54e1\u5de5\u7684\u5e73\u5747\u85aa\u6c34\uff0c\u4e26\u5c07\u7d50\u679c\u547d\u540d\u70ba average_salary<\/code>\u3002<\/p>\n
GROUP BY \u5b50\u53e5<\/h2>\n
\u7576\u6211\u5011\u9700\u8981\u6839\u64da\u67d0\u500b\u5217\u9032\u884c\u5206\u7d44\u6642\uff0c\u53ef\u4ee5\u4f7f\u7528 GROUP BY<\/code> \u5b50\u53e5\u3002\u4f8b\u5982\uff0c\u5982\u679c\u6211\u5011\u60f3\u8981\u6309\u8077\u4f4d\u8a08\u7b97\u6bcf\u500b\u8077\u4f4d\u7684\u54e1\u5de5\u6578\u91cf\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u8a9e\u53e5\uff1a<\/p>\n
SELECT position, COUNT(*) AS num_employees\nFROM employees\nGROUP BY position;<\/code><\/pre>\n
\u9019\u5c07\u8fd4\u56de\u6bcf\u500b\u8077\u4f4d\u53ca\u5176\u5c0d\u61c9\u7684\u54e1\u5de5\u6578\u91cf\u3002<\/p>\n
\u7d50\u5408\u591a\u500b\u689d\u4ef6<\/h2>\n
\u5728\u67e5\u8a62\u4e2d\uff0c\u6211\u5011\u53ef\u4ee5\u4f7f\u7528 AND<\/code> \u548c OR<\/code> \u4f86\u7d50\u5408\u591a\u500b\u689d\u4ef6\u3002\u4f8b\u5982\uff0c\u4ee5\u4e0b\u67e5\u8a62\u5c07\u8fd4\u56de\u85aa\u6c34\u9ad8\u65bc 50000 \u4e14\u8077\u4f4d\u70ba ‘Manager’ \u7684\u54e1\u5de5\uff1a<\/p>\n
SELECT name, salary\nFROM employees\nWHERE salary > 50000 AND position = 'Manager';<\/code><\/pre>\n
\u5c0f\u7d50<\/h2>\n
PostgreSQL \u7684 SELECT \u8a9e\u53e5\u662f\u6578\u64da\u67e5\u8a62\u7684\u57fa\u790e\uff0c\u901a\u904e\u9748\u6d3b\u904b\u7528\u5404\u7a2e\u5b50\u53e5\u548c\u51fd\u6578\uff0c\u6211\u5011\u53ef\u4ee5\u9ad8\u6548\u5730\u5f9e\u6578\u64da\u5eab\u4e2d\u63d0\u53d6\u6240\u9700\u7684\u4fe1\u606f\u3002\u7121\u8ad6\u662f\u57fa\u672c\u67e5\u8a62\u3001\u6578\u64da\u904e\u6ffe\u3001\u6392\u5e8f\u9084\u662f\u805a\u5408\uff0c\u638c\u63e1\u9019\u4e9b\u57fa\u672c\u64cd\u4f5c\u5c0d\u65bc\u6578\u64da\u5206\u6790\u548c\u61c9\u7528\u958b\u767c\u90fd\u662f\u81f3\u95dc\u91cd\u8981\u7684\u3002<\/p>\n
\u5982\u679c\u60a8\u6b63\u5728\u5c0b\u627e\u9ad8\u6548\u7684 VPS<\/a> \u89e3\u6c7a\u65b9\u6848\u4f86\u904b\u884c\u60a8\u7684 PostgreSQL \u6578\u64da\u5eab\uff0cServer.HK \u63d0\u4f9b\u4e86\u591a\u7a2e\u9078\u64c7\uff0c\u6eff\u8db3\u4e0d\u540c\u9700\u6c42\u7684\u7528\u6236\u3002\u7121\u8ad6\u662f \u9999\u6e2fVPS<\/a> \u9084\u662f\u5176\u4ed6\u985e\u578b\u7684 \u4e91\u670d\u52a1\u5668<\/a>\uff0c\u6211\u5011\u90fd\u80fd\u70ba\u60a8\u63d0\u4f9b\u7a69\u5b9a\u7684\u652f\u6301\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u5b78\u7fd2PostgreSQL SELECT\u8a9e\u53e5\u7684\u57fa\u672c\u7528\u6cd5\uff0c\u638c\u63e1\u6578\u64da\u67e5\u8a62\u6280\u5de7\uff0c\u63d0\u5347\u6578\u64da\u5eab\u64cd\u4f5c\u6548\u7387\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-160649","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/160649","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=160649"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/160649\/revisions"}],"predecessor-version":[{"id":160650,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/160649\/revisions\/160650"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=160649"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=160649"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=160649"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}