{"id":168537,"date":"2024-11-06T13:12:21","date_gmt":"2024-11-06T05:12:21","guid":{"rendered":"https:\/\/server.hk\/cnblog\/168537\/"},"modified":"2024-11-06T13:12:22","modified_gmt":"2024-11-06T05:12:22","slug":"sql-%e4%b8%ad%e8%bf%94%e5%9b%9e%e8%a8%88%e7%ae%97%e8%a1%a8%e9%81%94%e5%bc%8f%e7%9a%84%e5%87%bd%e6%95%b8","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/168537\/","title":{"rendered":"SQL \u4e2d\u8fd4\u56de\u8a08\u7b97\u8868\u9054\u5f0f\u7684\u51fd\u6578"},"content":{"rendered":"<h1 id=\"sql-%e4%b8%ad%e8%bf%94%e5%9b%9e%e8%a8%88%e7%ae%97%e8%a1%a8%e9%81%94%e5%bc%8f%e7%9a%84%e5%87%bd%e6%95%b8-uFOVkNJaIZ\">SQL \u4e2d\u8fd4\u56de\u8a08\u7b97\u8868\u9054\u5f0f\u7684\u51fd\u6578<\/h1>\n<p>\u5728\u8cc7\u6599\u5eab\u7ba1\u7406\u7cfb\u7d71\u4e2d\uff0cSQL\uff08\u7d50\u69cb\u5316\u67e5\u8a62\u8a9e\u8a00\uff09\u662f\u4e00\u7a2e\u7528\u65bc\u67e5\u8a62\u548c\u64cd\u4f5c\u8cc7\u6599\u7684\u6a19\u6e96\u8a9e\u8a00\u3002SQL \u63d0\u4f9b\u4e86\u591a\u7a2e\u51fd\u6578\u4f86\u8655\u7406\u6578\u64da\uff0c\u5176\u4e2d\u5305\u62ec\u8fd4\u56de\u8a08\u7b97\u8868\u9054\u5f0f\u7684\u51fd\u6578\u3002\u9019\u4e9b\u51fd\u6578\u80fd\u5920\u5e6b\u52a9\u7528\u6236\u5728\u67e5\u8a62\u4e2d\u9032\u884c\u6578\u5b78\u8a08\u7b97\u3001\u5b57\u4e32\u64cd\u4f5c\u548c\u65e5\u671f\u8655\u7406\u7b49\uff0c\u5f9e\u800c\u63d0\u9ad8\u6578\u64da\u8655\u7406\u7684\u6548\u7387\u548c\u9748\u6d3b\u6027\u3002<\/p>\n<h2 id=\"%e8%a8%88%e7%ae%97%e8%a1%a8%e9%81%94%e5%bc%8f%e7%9a%84%e5%9f%ba%e6%9c%ac%e6%a6%82%e5%bf%b5-uFOVkNJaIZ\">\u8a08\u7b97\u8868\u9054\u5f0f\u7684\u57fa\u672c\u6982\u5ff5<\/h2>\n<p>\u8a08\u7b97\u8868\u9054\u5f0f\u662f\u6307\u5728 SQL \u67e5\u8a62\u4e2d\u4f7f\u7528\u7684\u6578\u5b78\u904b\u7b97\u6216\u908f\u8f2f\u904b\u7b97\u3002\u9019\u4e9b\u8868\u9054\u5f0f\u53ef\u4ee5\u662f\u7c21\u55ae\u7684\u6578\u5b57\u904b\u7b97\uff0c\u4f8b\u5982\u52a0\u6cd5\u3001\u6e1b\u6cd5\u3001\u4e58\u6cd5\u548c\u9664\u6cd5\uff0c\u4e5f\u53ef\u4ee5\u662f\u66f4\u8907\u96dc\u7684\u904b\u7b97\uff0c\u5982\u4f7f\u7528\u51fd\u6578\u9032\u884c\u7684\u8a08\u7b97\u3002SQL \u4e2d\u7684\u8a08\u7b97\u8868\u9054\u5f0f\u901a\u5e38\u7528\u65bc SELECT \u8a9e\u53e5\u4e2d\uff0c\u4ee5\u4fbf\u5f9e\u8cc7\u6599\u5eab\u4e2d\u63d0\u53d6\u548c\u8a08\u7b97\u6240\u9700\u7684\u6578\u64da\u3002<\/p>\n<h2 id=\"%e5%b8%b8%e7%94%a8%e7%9a%84-sql-%e8%a8%88%e7%ae%97%e5%87%bd%e6%95%b8-uFOVkNJaIZ\">\u5e38\u7528\u7684 SQL \u8a08\u7b97\u51fd\u6578<\/h2>\n<p>\u4ee5\u4e0b\u662f\u4e00\u4e9b\u5e38\u7528\u7684 SQL \u8a08\u7b97\u51fd\u6578\uff0c\u9019\u4e9b\u51fd\u6578\u53ef\u4ee5\u5728\u67e5\u8a62\u4e2d\u8fd4\u56de\u8a08\u7b97\u7d50\u679c\uff1a<\/p>\n<ul>\n<li><strong>SUM()<\/strong>\uff1a\u8a08\u7b97\u6307\u5b9a\u5217\u7684\u7e3d\u548c\u3002<\/li>\n<li><strong>AVG()<\/strong>\uff1a\u8a08\u7b97\u6307\u5b9a\u5217\u7684\u5e73\u5747\u503c\u3002<\/li>\n<li><strong>COUNT()<\/strong>\uff1a\u8a08\u7b97\u6307\u5b9a\u5217\u7684\u884c\u6578\u3002<\/li>\n<li><strong>MIN()<\/strong>\uff1a\u8fd4\u56de\u6307\u5b9a\u5217\u7684\u6700\u5c0f\u503c\u3002<\/li>\n<li><strong>MAX()<\/strong>\uff1a\u8fd4\u56de\u6307\u5b9a\u5217\u7684\u6700\u5927\u503c\u3002<\/li>\n<\/ul>\n<h3 id=\"%e7%a4%ba%e4%be%8b%ef%bc%9a%e4%bd%bf%e7%94%a8-sum-%e5%87%bd%e6%95%b8-uFOVkNJaIZ\">\u793a\u4f8b\uff1a\u4f7f\u7528 SUM() \u51fd\u6578<\/h3>\n<pre><code>SELECT SUM(salary) AS total_salary\nFROM employees;<\/code><\/pre>\n<p>\u5728\u9019\u500b\u4f8b\u5b50\u4e2d\uff0cSUM() \u51fd\u6578\u7528\u65bc\u8a08\u7b97 employees \u8868\u4e2d\u6240\u6709\u54e1\u5de5\u7684\u85aa\u8cc7\u7e3d\u548c\uff0c\u4e26\u5c07\u7d50\u679c\u547d\u540d\u70ba total_salary\u3002<\/p>\n<h3 id=\"%e7%a4%ba%e4%be%8b%ef%bc%9a%e4%bd%bf%e7%94%a8-avg-%e5%87%bd%e6%95%b8-uFOVkNJaIZ\">\u793a\u4f8b\uff1a\u4f7f\u7528 AVG() \u51fd\u6578<\/h3>\n<pre><code>SELECT AVG(salary) AS average_salary\nFROM employees;<\/code><\/pre>\n<p>\u9019\u500b\u67e5\u8a62\u4f7f\u7528 AVG() \u51fd\u6578\u4f86\u8a08\u7b97 employees \u8868\u4e2d\u6240\u6709\u54e1\u5de5\u85aa\u8cc7\u7684\u5e73\u5747\u503c\u3002<\/p>\n<h2 id=\"%e5%ad%97%e4%b8%b2%e5%92%8c%e6%97%a5%e6%9c%9f%e7%9a%84%e8%a8%88%e7%ae%97%e5%87%bd%e6%95%b8-uFOVkNJaIZ\">\u5b57\u4e32\u548c\u65e5\u671f\u7684\u8a08\u7b97\u51fd\u6578<\/h2>\n<p>\u9664\u4e86\u6578\u5b78\u8a08\u7b97\uff0cSQL \u9084\u63d0\u4f9b\u4e86\u5b57\u4e32\u548c\u65e5\u671f\u7684\u8a08\u7b97\u51fd\u6578\u3002\u4f8b\u5982\uff1a<\/p>\n<ul>\n<li><strong>CONCAT()<\/strong>\uff1a\u7528\u65bc\u9023\u63a5\u5169\u500b\u6216\u591a\u500b\u5b57\u4e32\u3002<\/li>\n<li><strong>DATEDIFF()<\/strong>\uff1a\u8a08\u7b97\u5169\u500b\u65e5\u671f\u4e4b\u9593\u7684\u5dee\u7570\u3002<\/li>\n<\/ul>\n<h3 id=\"%e7%a4%ba%e4%be%8b%ef%bc%9a%e4%bd%bf%e7%94%a8-concat-%e5%87%bd%e6%95%b8-uFOVkNJaIZ\">\u793a\u4f8b\uff1a\u4f7f\u7528 CONCAT() \u51fd\u6578<\/h3>\n<pre><code>SELECT CONCAT(first_name, ' ', last_name) AS full_name\nFROM employees;<\/code><\/pre>\n<p>\u9019\u500b\u67e5\u8a62\u5c07 employees \u8868\u4e2d\u7684\u540d\u5b57\u548c\u59d3\u6c0f\u9023\u63a5\u8d77\u4f86\uff0c\u751f\u6210\u5b8c\u6574\u7684\u59d3\u540d\u3002<\/p>\n<h3 id=\"%e7%a4%ba%e4%be%8b%ef%bc%9a%e4%bd%bf%e7%94%a8-datediff-%e5%87%bd%e6%95%b8-uFOVkNJaIZ\">\u793a\u4f8b\uff1a\u4f7f\u7528 DATEDIFF() \u51fd\u6578<\/h3>\n<pre><code>SELECT DATEDIFF(NOW(), hire_date) AS days_since_hired\nFROM employees;<\/code><\/pre>\n<p>\u9019\u500b\u67e5\u8a62\u8a08\u7b97\u5f9e\u54e1\u5de5\u5165\u8077\u65e5\u671f\u5230\u73fe\u5728\u7684\u5929\u6578\u3002<\/p>\n<h2 id=\"%e7%b5%90%e8%ab%96-uFOVkNJaIZ\">\u7d50\u8ad6<\/h2>\n<p>SQL \u4e2d\u7684\u8a08\u7b97\u8868\u9054\u5f0f\u51fd\u6578\u70ba\u6578\u64da\u5206\u6790\u548c\u5831\u544a\u63d0\u4f9b\u4e86\u5f37\u5927\u7684\u5de5\u5177\u3002\u901a\u904e\u4f7f\u7528\u9019\u4e9b\u51fd\u6578\uff0c\u958b\u767c\u8005\u548c\u6578\u64da\u5206\u6790\u5e2b\u53ef\u4ee5\u8f15\u9b06\u5730\u5f9e\u8cc7\u6599\u5eab\u4e2d\u63d0\u53d6\u6709\u50f9\u503c\u7684\u4fe1\u606f\uff0c\u9032\u884c\u5404\u7a2e\u8a08\u7b97\u548c\u5206\u6790\u3002\u7121\u8ad6\u662f\u9032\u884c\u6578\u5b78\u904b\u7b97\u3001\u5b57\u4e32\u8655\u7406\u9084\u662f\u65e5\u671f\u8a08\u7b97\uff0c\u9019\u4e9b\u51fd\u6578\u90fd\u80fd\u5920\u63d0\u9ad8\u5de5\u4f5c\u6548\u7387\uff0c\u5e6b\u52a9\u7528\u6236\u66f4\u597d\u5730\u7406\u89e3\u548c\u5229\u7528\u6578\u64da\u3002<\/p>\n<p>\u5982\u679c\u60a8\u5c0d\u65bc <a href=\"https:\/\/server.hk\">\u9999\u6e2f VPS<\/a> \u670d\u52d9\u6709\u8208\u8da3\uff0c\u6216\u60f3\u4e86\u89e3\u66f4\u591a\u95dc\u65bc <a href=\"https:\/\/server.hk\">\u4f3a\u670d\u5668<\/a> \u7684\u8cc7\u8a0a\uff0c\u6b61\u8fce\u8a2a\u554f\u6211\u5011\u7684\u7db2\u7ad9\u4ee5\u7372\u53d6\u66f4\u591a\u8a73\u7d30\u8cc7\u6599\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u63a2\u7d22 SQL \u4e2d\u8fd4\u56de\u8a08\u7b97\u8868\u9054\u5f0f\u7684\u51fd\u6578\uff0c\u4e86\u89e3\u5982\u4f55\u4f7f\u7528\u9019\u4e9b\u51fd\u6578\u9032\u884c\u6578\u64da\u8655\u7406\u548c\u5206\u6790\uff0c\u63d0\u5347\u67e5\u8a62\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-168537","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/168537","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=168537"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/168537\/revisions"}],"predecessor-version":[{"id":168538,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/168537\/revisions\/168538"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=168537"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=168537"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=168537"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}