{"id":143809,"date":"2024-11-01T01:26:19","date_gmt":"2024-10-31T17:26:19","guid":{"rendered":"https:\/\/server.hk\/cnblog\/143809\/"},"modified":"2024-11-01T01:26:20","modified_gmt":"2024-10-31T17:26:20","slug":"sql-%e5%87%bd%e6%95%b8%e7%9a%84%e6%a0%bc%e5%bc%8f","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/143809\/","title":{"rendered":"SQL \u51fd\u6578\u7684\u683c\u5f0f"},"content":{"rendered":"<h1 id=\"sql-%e5%87%bd%e6%95%b8%e7%9a%84%e6%a0%bc%e5%bc%8f-EDOWMgbjdm\">SQL \u51fd\u6578\u7684\u683c\u5f0f<\/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 \u51fd\u6578\u662f SQL \u8a9e\u8a00\u4e2d\u7684\u4e00\u500b\u91cd\u8981\u7d44\u6210\u90e8\u5206\uff0c\u80fd\u5920\u5e6b\u52a9\u7528\u6236\u9032\u884c\u5404\u7a2e\u6578\u64da\u8655\u7406\u548c\u8a08\u7b97\u3002\u672c\u6587\u5c07\u63a2\u8a0e SQL \u51fd\u6578\u7684\u683c\u5f0f\u3001\u985e\u578b\u53ca\u5176\u4f7f\u7528\u7bc4\u4f8b\u3002<\/p>\n<h2 id=\"sql-%e5%87%bd%e6%95%b8%e7%9a%84%e5%9f%ba%e6%9c%ac%e6%a0%bc%e5%bc%8f-EDOWMgbjdm\">SQL \u51fd\u6578\u7684\u57fa\u672c\u683c\u5f0f<\/h2>\n<p>SQL \u51fd\u6578\u7684\u57fa\u672c\u683c\u5f0f\u901a\u5e38\u5982\u4e0b\uff1a<\/p>\n<pre><code>FUNCTION_NAME(argument1, argument2, ...)<\/code><\/pre>\n<p>\u5728\u9019\u88e1\uff0c<code>FUNCTION_NAME<\/code> \u662f\u51fd\u6578\u7684\u540d\u7a31\uff0c\u800c <code>argument<\/code> \u662f\u50b3\u905e\u7d66\u51fd\u6578\u7684\u53c3\u6578\u3002\u6839\u64da\u4e0d\u540c\u7684\u51fd\u6578\uff0c\u53c3\u6578\u7684\u6578\u91cf\u548c\u985e\u578b\u53ef\u80fd\u6703\u6709\u6240\u4e0d\u540c\u3002<\/p>\n<h2 id=\"sql-%e5%87%bd%e6%95%b8%e7%9a%84%e9%a1%9e%e5%9e%8b-EDOWMgbjdm\">SQL \u51fd\u6578\u7684\u985e\u578b<\/h2>\n<p>SQL \u51fd\u6578\u53ef\u4ee5\u5206\u70ba\u5e7e\u500b\u4e3b\u8981\u985e\u578b\uff0c\u5305\u62ec\uff1a<\/p>\n<ul>\n<li><strong>\u805a\u5408\u51fd\u6578<\/strong>\uff1a\u9019\u4e9b\u51fd\u6578\u7528\u65bc\u5c0d\u4e00\u7d44\u503c\u9032\u884c\u8a08\u7b97\uff0c\u4e26\u8fd4\u56de\u55ae\u4e00\u503c\u3002\u5e38\u898b\u7684\u805a\u5408\u51fd\u6578\u5305\u62ec\uff1a<\/li>\n<ul>\n<li><code>COUNT()<\/code>\uff1a\u8a08\u7b97\u884c\u6578\u3002<\/li>\n<li><code>SUM()<\/code>\uff1a\u8a08\u7b97\u6578\u503c\u7684\u7e3d\u548c\u3002<\/li>\n<li><code>AVG()<\/code>\uff1a\u8a08\u7b97\u6578\u503c\u7684\u5e73\u5747\u503c\u3002<\/li>\n<li><code>MAX()<\/code>\uff1a\u8fd4\u56de\u6700\u5927\u503c\u3002<\/li>\n<li><code>MIN()<\/code>\uff1a\u8fd4\u56de\u6700\u5c0f\u503c\u3002<\/li>\n<\/ul>\n<\/ul>\n<h3 id=\"%e8%81%9a%e5%90%88%e5%87%bd%e6%95%b8%e7%af%84%e4%be%8b-EDOWMgbjdm\">\u805a\u5408\u51fd\u6578\u7bc4\u4f8b<\/h3>\n<p>\u4ee5\u4e0b\u662f\u4e00\u500b\u4f7f\u7528\u805a\u5408\u51fd\u6578\u7684\u7bc4\u4f8b\uff1a<\/p>\n<pre><code>SELECT COUNT(*) AS total_users FROM users;<\/code><\/pre>\n<p>\u9019\u689d\u67e5\u8a62\u5c07\u8fd4\u56de\u7528\u6236\u8868\u4e2d\u7684\u7e3d\u7528\u6236\u6578\u3002<\/p>\n<ul>\n<li><strong>\u6a19\u91cf\u51fd\u6578<\/strong>\uff1a\u9019\u4e9b\u51fd\u6578\u5c0d\u55ae\u4e00\u503c\u9032\u884c\u8a08\u7b97\uff0c\u4e26\u8fd4\u56de\u55ae\u4e00\u503c\u3002\u5e38\u898b\u7684\u6a19\u91cf\u51fd\u6578\u5305\u62ec\uff1a<\/li>\n<ul>\n<li><code>UPPER()<\/code>\uff1a\u5c07\u5b57\u4e32\u8f49\u63db\u70ba\u5927\u5beb\u3002<\/li>\n<li><code>LOWER()<\/code>\uff1a\u5c07\u5b57\u4e32\u8f49\u63db\u70ba\u5c0f\u5beb\u3002<\/li>\n<li><code>LENGTH()<\/code>\uff1a\u8fd4\u56de\u5b57\u4e32\u7684\u9577\u5ea6\u3002<\/li>\n<li><code>ROUND()<\/code>\uff1a\u5c0d\u6578\u503c\u9032\u884c\u56db\u6368\u4e94\u5165\u3002<\/li>\n<\/ul>\n<\/ul>\n<h3 id=\"%e6%a8%99%e9%87%8f%e5%87%bd%e6%95%b8%e7%af%84%e4%be%8b-EDOWMgbjdm\">\u6a19\u91cf\u51fd\u6578\u7bc4\u4f8b<\/h3>\n<p>\u4ee5\u4e0b\u662f\u4e00\u500b\u4f7f\u7528\u6a19\u91cf\u51fd\u6578\u7684\u7bc4\u4f8b\uff1a<\/p>\n<pre><code>SELECT UPPER(username) AS uppercase_username FROM users;<\/code><\/pre>\n<p>\u9019\u689d\u67e5\u8a62\u5c07\u8fd4\u56de\u7528\u6236\u540d\u7684\u5168\u5927\u5beb\u5f62\u5f0f\u3002<\/p>\n<h2 id=\"%e8%87%aa%e5%ae%9a%e7%be%a9%e5%87%bd%e6%95%b8-EDOWMgbjdm\">\u81ea\u5b9a\u7fa9\u51fd\u6578<\/h2>\n<p>\u9664\u4e86\u5167\u5efa\u7684 SQL \u51fd\u6578\uff0c\u4f7f\u7528\u8005\u9084\u53ef\u4ee5\u5275\u5efa\u81ea\u5b9a\u7fa9\u51fd\u6578\u3002\u81ea\u5b9a\u7fa9\u51fd\u6578\u7684\u683c\u5f0f\u5982\u4e0b\uff1a<\/p>\n<pre><code>CREATE FUNCTION function_name (parameters)\nRETURNS return_type\nAS\nBEGIN\n    -- function body\n    RETURN value;\nEND;<\/code><\/pre>\n<p>\u81ea\u5b9a\u7fa9\u51fd\u6578\u53ef\u4ee5\u6839\u64da\u7279\u5b9a\u9700\u6c42\u9032\u884c\u8a2d\u8a08\uff0c\u4e26\u5728\u67e5\u8a62\u4e2d\u4f7f\u7528\u3002<\/p>\n<h3 id=\"%e8%87%aa%e5%ae%9a%e7%be%a9%e5%87%bd%e6%95%b8%e7%af%84%e4%be%8b-EDOWMgbjdm\">\u81ea\u5b9a\u7fa9\u51fd\u6578\u7bc4\u4f8b<\/h3>\n<p>\u4ee5\u4e0b\u662f\u4e00\u500b\u7c21\u55ae\u7684\u81ea\u5b9a\u7fa9\u51fd\u6578\u7bc4\u4f8b\uff1a<\/p>\n<pre><code>CREATE FUNCTION get_full_name (first_name VARCHAR(50), last_name VARCHAR(50))\nRETURNS VARCHAR(101)\nAS\nBEGIN\n    RETURN CONCAT(first_name, ' ', last_name);\nEND;<\/code><\/pre>\n<p>\u9019\u500b\u51fd\u6578\u5c07\u8fd4\u56de\u5168\u540d\uff0c\u4e26\u53ef\u4ee5\u5728\u67e5\u8a62\u4e2d\u4f7f\u7528\uff1a<\/p>\n<pre><code>SELECT get_full_name(first_name, last_name) AS full_name FROM users;<\/code><\/pre>\n<h2 id=\"%e7%b8%bd%e7%b5%90-EDOWMgbjdm\">\u7e3d\u7d50<\/h2>\n<p>SQL \u51fd\u6578\u5728\u8cc7\u6599\u5eab\u64cd\u4f5c\u4e2d\u626e\u6f14\u8457\u91cd\u8981\u7684\u89d2\u8272\uff0c\u7121\u8ad6\u662f\u9032\u884c\u6578\u64da\u8a08\u7b97\u9084\u662f\u8655\u7406\u5b57\u4e32\uff0c\u5747\u80fd\u63d0\u9ad8\u67e5\u8a62\u7684\u6548\u7387\u548c\u9748\u6d3b\u6027\u3002\u4e86\u89e3 SQL \u51fd\u6578\u7684\u683c\u5f0f\u548c\u985e\u578b\uff0c\u80fd\u5e6b\u52a9\u958b\u767c\u8005\u66f4\u6709\u6548\u5730\u4f7f\u7528\u8cc7\u6599\u5eab\u3002\u82e5\u60a8\u5c0d\u65bc <a href=\"https:\/\/server.hk\">\u9999\u6e2f VPS<\/a> \u53ca\u5176\u76f8\u95dc\u670d\u52d9\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":"<p>\u4e86\u89e3 SQL \u51fd\u6578\u7684\u683c\u5f0f\uff0c\u5305\u62ec\u8a9e\u6cd5\u7d50\u69cb\u3001\u53c3\u6578\u4f7f\u7528\u53ca\u7bc4\u4f8b\uff0c\u5e6b\u52a9\u60a8\u6709\u6548\u5730\u7de8\u5beb\u548c\u512a\u5316\u67e5\u8a62\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-143809","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/143809","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=143809"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/143809\/revisions"}],"predecessor-version":[{"id":143810,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/143809\/revisions\/143810"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=143809"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=143809"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=143809"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}