{"id":175649,"date":"2024-11-08T07:38:17","date_gmt":"2024-11-07T23:38:17","guid":{"rendered":"https:\/\/server.hk\/cnblog\/175649\/"},"modified":"2024-11-08T07:38:18","modified_gmt":"2024-11-07T23:38:18","slug":"%e5%a6%82%e4%bd%95%e5%af%ab%e5%87%ba%e9%ab%98%e8%b3%aa%e9%87%8f%e7%9a%84sql%e4%bb%a3%e7%a2%bc%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/175649\/","title":{"rendered":"\u5982\u4f55\u5beb\u51fa\u9ad8\u8cea\u91cf\u7684SQL\u4ee3\u78bc\uff1f"},"content":{"rendered":"<h1 id=\"%e5%a6%82%e4%bd%95%e5%af%ab%e5%87%ba%e9%ab%98%e8%b3%aa%e9%87%8f%e7%9a%84sql%e4%bb%a3%e7%a2%bc%ef%bc%9f-QnlmuPMuFL\">\u5982\u4f55\u5beb\u51fa\u9ad8\u8cea\u91cf\u7684SQL\u4ee3\u78bc\uff1f<\/h1>\n<p>\u5728\u7576\u4eca\u6578\u64da\u9a45\u52d5\u7684\u4e16\u754c\u4e2d\uff0cSQL\uff08\u7d50\u69cb\u5316\u67e5\u8a62\u8a9e\u8a00\uff09\u662f\u8207\u6578\u64da\u5eab\u9032\u884c\u4ea4\u4e92\u7684\u4e3b\u8981\u5de5\u5177\u3002\u7121\u8ad6\u662f\u958b\u767c\u61c9\u7528\u7a0b\u5e8f\u9084\u662f\u9032\u884c\u6578\u64da\u5206\u6790\uff0c\u64b0\u5beb\u9ad8\u8cea\u91cf\u7684SQL\u4ee3\u78bc\u90fd\u662f\u81f3\u95dc\u91cd\u8981\u7684\u3002\u9ad8\u8cea\u91cf\u7684SQL\u4ee3\u78bc\u4e0d\u50c5\u80fd\u63d0\u9ad8\u67e5\u8a62\u6027\u80fd\uff0c\u9084\u80fd\u589e\u5f37\u4ee3\u78bc\u7684\u53ef\u8b80\u6027\u548c\u53ef\u7dad\u8b77\u6027\u3002\u672c\u6587\u5c07\u63a2\u8a0e\u4e00\u4e9b\u64b0\u5beb\u9ad8\u8cea\u91cfSQL\u4ee3\u78bc\u7684\u6700\u4f73\u5be6\u8e10\u3002<\/p>\n<h2 id=\"1-%e4%bd%bf%e7%94%a8%e6%b8%85%e6%99%b0%e7%9a%84%e5%91%bd%e5%90%8d%e8%a6%8f%e5%89%87-QnlmuPMuFL\">1. \u4f7f\u7528\u6e05\u6670\u7684\u547d\u540d\u898f\u5247<\/h2>\n<p>\u5728\u64b0\u5bebSQL\u4ee3\u78bc\u6642\uff0c\u4f7f\u7528\u6e05\u6670\u4e14\u4e00\u81f4\u7684\u547d\u540d\u898f\u5247\u662f\u975e\u5e38\u91cd\u8981\u7684\u3002\u8868\u540d\u3001\u5217\u540d\u548c\u5176\u4ed6\u5c0d\u8c61\u7684\u540d\u7a31\u61c9\u8a72\u80fd\u5920\u6e05\u695a\u5730\u8868\u9054\u5176\u5167\u5bb9\u548c\u7528\u9014\u3002\u4f8b\u5982\uff0c\u4f7f\u7528 <code>customer_orders<\/code> \u800c\u4e0d\u662f <code>co<\/code> \u4f86\u8868\u793a\u5ba2\u6236\u8a02\u55ae\u8868\u3002\u9019\u6a23\u53ef\u4ee5\u63d0\u9ad8\u4ee3\u78bc\u7684\u53ef\u8b80\u6027\uff0c\u8b93\u5176\u4ed6\u958b\u767c\u8005\u66f4\u5bb9\u6613\u7406\u89e3\u3002<\/p>\n<h2 id=\"2-%e9%81%a9%e7%95%b6%e4%bd%bf%e7%94%a8%e8%a8%bb%e9%87%8b-QnlmuPMuFL\">2. \u9069\u7576\u4f7f\u7528\u8a3b\u91cb<\/h2>\n<p>\u5728SQL\u4ee3\u78bc\u4e2d\u6dfb\u52a0\u8a3b\u91cb\u53ef\u4ee5\u5e6b\u52a9\u5176\u4ed6\u958b\u767c\u8005\u7406\u89e3\u4ee3\u78bc\u7684\u908f\u8f2f\u548c\u76ee\u7684\u3002\u4f7f\u7528 <code>--<\/code> \u4f86\u6dfb\u52a0\u55ae\u884c\u8a3b\u91cb\uff0c\u6216\u4f7f\u7528 <code>\/* ... *\/<\/code> \u4f86\u6dfb\u52a0\u591a\u884c\u8a3b\u91cb\u3002\u4f8b\u5982\uff1a<\/p>\n<pre><code>-- \u9019\u662f\u67e5\u8a62\u6240\u6709\u5ba2\u6236\u7684\u8a02\u55ae\nSELECT * FROM customer_orders;<\/code><\/pre>\n<h2 id=\"3-%e5%84%aa%e5%8c%96%e6%9f%a5%e8%a9%a2%e6%80%a7%e8%83%bd-QnlmuPMuFL\">3. \u512a\u5316\u67e5\u8a62\u6027\u80fd<\/h2>\n<p>\u64b0\u5beb\u9ad8\u6548\u7684SQL\u67e5\u8a62\u662f\u63d0\u9ad8\u6027\u80fd\u7684\u95dc\u9375\u3002\u4ee5\u4e0b\u662f\u4e00\u4e9b\u512a\u5316\u67e5\u8a62\u6027\u80fd\u7684\u6280\u5de7\uff1a<\/p>\n<ul>\n<li><strong>\u4f7f\u7528\u7d22\u5f15\uff1a<\/strong>\u70ba\u7d93\u5e38\u67e5\u8a62\u7684\u5217\u5275\u5efa\u7d22\u5f15\uff0c\u53ef\u4ee5\u986f\u8457\u63d0\u9ad8\u67e5\u8a62\u901f\u5ea6\u3002<\/li>\n<li><strong>\u907f\u514d\u4f7f\u7528SELECT *\uff1a<\/strong>\u660e\u78ba\u6307\u5b9a\u6240\u9700\u7684\u5217\uff0c\u9019\u6a23\u53ef\u4ee5\u6e1b\u5c11\u6578\u64da\u50b3\u8f38\u91cf\u3002<\/li>\n<li><strong>\u4f7f\u7528JOIN\u800c\u4e0d\u662f\u5b50\u67e5\u8a62\uff1a<\/strong>\u5728\u8a31\u591a\u60c5\u6cc1\u4e0b\uff0c\u4f7f\u7528JOIN\u53ef\u4ee5\u63d0\u9ad8\u67e5\u8a62\u6027\u80fd\u3002<\/li>\n<\/ul>\n<p>\u4f8b\u5982\uff0c\u4ee5\u4e0b\u67e5\u8a62\u4f7f\u7528JOIN\u4f86\u7372\u53d6\u5ba2\u6236\u53ca\u5176\u8a02\u55ae\uff1a<\/p>\n<pre><code>SELECT c.customer_name, o.order_date\nFROM customers c\nJOIN orders o ON c.customer_id = o.customer_id;<\/code><\/pre>\n<h2 id=\"4-%e9%81%a9%e7%95%b6%e8%99%95%e7%90%86null%e5%80%bc-QnlmuPMuFL\">4. \u9069\u7576\u8655\u7406NULL\u503c<\/h2>\n<p>\u5728\u6578\u64da\u5eab\u4e2d\uff0cNULL\u503c\u7684\u8655\u7406\u81f3\u95dc\u91cd\u8981\u3002\u64b0\u5bebSQL\u4ee3\u78bc\u6642\uff0c\u61c9\u8a72\u8003\u616e\u5230NULL\u503c\u7684\u5b58\u5728\uff0c\u4e26\u4f7f\u7528\u9069\u7576\u7684\u51fd\u6578\u4f86\u8655\u7406\u5b83\u5011\u3002\u4f8b\u5982\uff0c\u53ef\u4ee5\u4f7f\u7528 <code>COALESCE<\/code> \u51fd\u6578\u4f86\u66ff\u63dbNULL\u503c\uff1a<\/p>\n<pre><code>SELECT customer_name, COALESCE(phone_number, '\u7121\u96fb\u8a71') AS phone_number\nFROM customers;<\/code><\/pre>\n<h2 id=\"5-%e6%b8%ac%e8%a9%a6%e5%92%8c%e8%aa%bf%e8%a9%a6-QnlmuPMuFL\">5. \u6e2c\u8a66\u548c\u8abf\u8a66<\/h2>\n<p>\u5728\u5c07SQL\u4ee3\u78bc\u6295\u5165\u751f\u7522\u4e4b\u524d\uff0c\u9032\u884c\u5145\u5206\u7684\u6e2c\u8a66\u548c\u8abf\u8a66\u662f\u5fc5\u8981\u7684\u3002\u53ef\u4ee5\u4f7f\u7528\u6e2c\u8a66\u6578\u64da\u4f86\u9a57\u8b49\u67e5\u8a62\u7684\u6b63\u78ba\u6027\u548c\u6027\u80fd\u3002\u78ba\u4fdd\u6240\u6709\u908a\u754c\u60c5\u6cc1\u90fd\u5f97\u5230\u4e86\u8003\u616e\uff0c\u4e26\u4e14\u67e5\u8a62\u80fd\u5920\u6b63\u78ba\u8655\u7406\u5404\u7a2e\u8f38\u5165\u3002<\/p>\n<h2 id=\"6-%e5%ae%9a%e6%9c%9f%e9%87%8d%e6%a7%8b%e4%bb%a3%e7%a2%bc-QnlmuPMuFL\">6. \u5b9a\u671f\u91cd\u69cb\u4ee3\u78bc<\/h2>\n<p>\u96a8\u8457\u6642\u9593\u7684\u63a8\u79fb\uff0c\u6578\u64da\u5eab\u7d50\u69cb\u548c\u696d\u52d9\u9700\u6c42\u53ef\u80fd\u6703\u767c\u751f\u8b8a\u5316\u3002\u5b9a\u671f\u91cd\u69cbSQL\u4ee3\u78bc\u53ef\u4ee5\u5e6b\u52a9\u4fdd\u6301\u4ee3\u78bc\u7684\u9ad8\u8cea\u91cf\uff0c\u4e26\u78ba\u4fdd\u5176\u8207\u7576\u524d\u9700\u6c42\u76f8\u7b26\u3002\u91cd\u69cb\u6642\uff0c\u61c9\u8a72\u8003\u616e\u5230\u6027\u80fd\u512a\u5316\u548c\u53ef\u8b80\u6027\u3002<\/p>\n<h2 id=\"%e7%b8%bd%e7%b5%90-QnlmuPMuFL\">\u7e3d\u7d50<\/h2>\n<p>\u64b0\u5beb\u9ad8\u8cea\u91cf\u7684SQL\u4ee3\u78bc\u9700\u8981\u9075\u5faa\u4e00\u4e9b\u6700\u4f73\u5be6\u8e10\uff0c\u5305\u62ec\u4f7f\u7528\u6e05\u6670\u7684\u547d\u540d\u898f\u5247\u3001\u9069\u7576\u4f7f\u7528\u8a3b\u91cb\u3001\u512a\u5316\u67e5\u8a62\u6027\u80fd\u3001\u8655\u7406NULL\u503c\u3001\u9032\u884c\u6e2c\u8a66\u548c\u8abf\u8a66\uff0c\u4ee5\u53ca\u5b9a\u671f\u91cd\u69cb\u4ee3\u78bc\u3002\u9019\u4e9b\u505a\u6cd5\u4e0d\u50c5\u80fd\u63d0\u9ad8\u4ee3\u78bc\u7684\u53ef\u8b80\u6027\u548c\u53ef\u7dad\u8b77\u6027\uff0c\u9084\u80fd\u63d0\u5347\u67e5\u8a62\u6027\u80fd\u3002\u5c0d\u65bc\u9700\u8981\u9ad8\u6548\u6578\u64da\u8655\u7406\u7684\u4f01\u696d\u4f86\u8aaa\uff0c\u9078\u64c7\u5408\u9069\u7684 <a href=\"https:\/\/server.hk\">VPS<\/a> \u89e3\u6c7a\u65b9\u6848\u4e5f\u662f\u81f3\u95dc\u91cd\u8981\u7684\uff0c\u9019\u6a23\u53ef\u4ee5\u78ba\u4fdd\u6578\u64da\u5eab\u904b\u884c\u7684\u7a69\u5b9a\u6027\u548c\u6548\u7387\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u5b78\u7fd2\u5982\u4f55\u5beb\u51fa\u9ad8\u8cea\u91cf\u7684SQL\u4ee3\u78bc\uff0c\u63d0\u5347\u67e5\u8a62\u6548\u7387\uff0c\u589e\u5f37\u53ef\u8b80\u6027\uff0c\u4e26\u78ba\u4fdd\u6578\u64da\u5b89\u5168\u8207\u7dad\u8b77\u6027\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-175649","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/175649","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=175649"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/175649\/revisions"}],"predecessor-version":[{"id":175650,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/175649\/revisions\/175650"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=175649"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=175649"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=175649"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}