{"id":5638,"date":"2024-11-14T08:13:21","date_gmt":"2024-11-14T00:13:21","guid":{"rendered":"https:\/\/fwq.ai\/blog\/5638\/"},"modified":"2024-11-14T08:13:21","modified_gmt":"2024-11-14T00:13:21","slug":"sql%e5%a4%9a%e8%a1%a8%e6%9f%a5%e8%af%a2%e8%af%ad%e5%8f%a5%e6%80%8e%e4%b9%88%e5%86%99","status":"publish","type":"post","link":"https:\/\/fwq.ai\/blog\/5638\/","title":{"rendered":"sql\u591a\u8868\u67e5\u8be2\u8bed\u53e5\u600e\u4e48\u5199"},"content":{"rendered":"<blockquote><p>\n  \u591a\u8868\u67e5\u8be2\u8bed\u53e5\u7528\u4e8e\u4ece\u591a\u4e2a\u8868\u4e2d\u83b7\u53d6\u6570\u636e\u3002\u53ef\u4f7f\u7528 join \u5173\u952e\u5b57\u6307\u5b9a\u8868\u5173\u7cfb\uff0c\u5e38\u7528\u7c7b\u578b\u4e3a\uff1ainner join\uff08\u5339\u914d\u884c\uff09\u3001left join\uff08\u5de6\u8868\u5168\u884c\uff0c\u53f3\u8868\u5339\u914d\u884c\u6216 null\uff09\u3001right join\uff08\u53f3\u8868\u5168\u884c\uff0c\u5de6\u8868\u5339\u914d\u884c\u6216 null\uff09\u3001full join\uff08\u4e24\u4e2a\u8868\u5168\u884c\uff09\u3002\u7f16\u5199\u6b65\u9aa4\uff1a\u786e\u5b9a\u8868\u3001\u6307\u5b9a join \u7c7b\u578b\u3001\u6307\u5b9a\u8fde\u63a5\u6761\u4ef6\u3001\u9009\u62e9\u663e\u793a\u5217\u3002\n<\/p><\/blockquote>\n<p><img decoding=\"async\" src=\"https:\/\/img.php.cn\/upload\/article\/202405\/30\/2024053019305661384.jpg\" class=\"aligncenter\" title=\"sql\u591a\u8868\u67e5\u8be2\u8bed\u53e5\u600e\u4e48\u5199\u63d2\u56fe\" alt=\"sql\u591a\u8868\u67e5\u8be2\u8bed\u53e5\u600e\u4e48\u5199\u63d2\u56fe\" \/><\/p>\n<p><strong>SQL \u591a\u8868\u67e5\u8be2\u8bed\u53e5<\/strong><\/p>\n<p><strong>\u5982\u4f55\u7f16\u5199\u591a\u8868\u67e5\u8be2\u8bed\u53e5\uff1f<\/strong><\/p>\n<p>\u591a\u8868\u67e5\u8be2\u8bed\u53e5\u7528\u4e8e\u4ece\u591a\u4e2a\u8868\u4e2d\u83b7\u53d6\u6570\u636e\u3002\u8981\u7f16\u5199\u591a\u8868\u67e5\u8be2\uff0c\u53ef\u4ee5\u4f7f\u7528 JOIN \u5173\u952e\u5b57\uff0c\u5b83\u6307\u5b9a\u8868\u4e4b\u95f4\u7684\u5173\u7cfb\u3002<\/p>\n<p><strong>\u5e38\u7528\u7684 JOIN \u7c7b\u578b\uff1a<\/strong><\/p>\n<ul>\n<li> <strong>INNER JOIN\uff1a<\/strong>\u4ec5\u8fd4\u56de\u5177\u6709\u5339\u914d\u884c\u7684\u6240\u6709\u884c\u3002<\/li>\n<li> <strong>LEFT JOIN\uff1a<\/strong>\u8fd4\u56de\u5de6\u8868\u7684\u5168\u90e8\u884c\uff0c\u4ee5\u53ca\u5339\u914d\u53f3\u8868\u884c\u7684\u53f3\u8868\u884c\u3002\u5982\u679c\u53f3\u8868\u4e2d\u6ca1\u6709\u5339\u914d\u9879\uff0c\u5219\u8fd4\u56de NULL\u3002<\/li>\n<li> <strong>RIGHT JOIN\uff1a<\/strong>\u4e0e LEFT JOIN \u76f8\u53cd\uff0c\u8fd4\u56de\u53f3\u8868\u7684\u5168\u90e8\u884c\u4ee5\u53ca\u5339\u914d\u5de6\u8868\u884c\u7684\u5de6\u8868\u884c\u3002<\/li>\n<li> <strong>FULL JOIN\uff1a<\/strong>\u8fd4\u56de\u4e24\u4e2a\u8868\u7684\u5168\u90e8\u884c\uff0c\u65e0\u8bba\u662f\u5426\u6709\u5339\u914d\u9879\u3002<\/li>\n<\/ul>\n<p><strong>\u7f16\u5199\u591a\u8868\u67e5\u8be2\u8bed\u53e5\u7684\u6b65\u9aa4\uff1a<\/strong><\/p>\n<ol>\n<li> <strong>\u786e\u5b9a\u8981\u8fde\u63a5\u7684\u8868\uff1a<\/strong>\u786e\u5b9a\u9700\u8981\u4ece\u54ea\u4e9b\u8868\u4e2d\u83b7\u53d6\u6570\u636e\u3002<\/li>\n<li> <strong>\u6307\u5b9a JOIN \u7c7b\u578b\uff1a<\/strong>\u6839\u636e\u9700\u8981\u9009\u62e9 INNER JOIN\u3001LEFT JOIN\u3001RIGHT JOIN \u6216 FULL JOIN\u3002<\/li>\n<li> <strong>\u6307\u5b9a\u8fde\u63a5\u6761\u4ef6\uff1a<\/strong>\u4f7f\u7528 ON \u5b50\u53e5\u6307\u5b9a\u8868\u4e4b\u95f4\u7684\u5339\u914d\u6761\u4ef6\u3002<\/li>\n<li> <strong>\u9009\u62e9\u8981\u663e\u793a\u7684\u5217\uff1a<\/strong>\u4f7f\u7528 SELECT \u5b50\u53e5\u9009\u62e9\u8981\u4ece\u8868\u4e2d\u663e\u793a\u7684\u5217\u3002<\/li>\n<\/ol>\n<p><strong>\u793a\u4f8b\uff1a<\/strong><\/p>\n<p>\u67e5\u8be2 Customers \u8868\u548c Orders \u8868\uff0c\u627e\u51fa\u6bcf\u4e2a\u5ba2\u6237\u7684\u59d3\u540d\u548c\u8ba2\u5355\u6570\u91cf\uff1a<\/p>\n<pre>SELECT c.Name, COUNT(o.OrderID) AS OrderCount\nFROM Customers c\nINNER JOIN Orders o ON c.CustomerID = o.CustomerID\nGROUP BY c.Name;<\/pre>\n<p>  \u767b\u5f55\u540e\u590d\u5236   <\/p>\n<p><strong>\u7ed3\u679c\uff1a<\/strong><\/p>\n<table>\n<thead>\n<tr>\n<th>Name<\/th>\n<th>OrderCount<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>John Doe<\/td>\n<td>3<\/td>\n<\/tr>\n<tr>\n<td>Jane Smith<\/td>\n<td>2<\/td>\n<\/tr>\n<tr>\n<td>Mike Jones<\/td>\n<td>4<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>\u4ee5\u4e0a\u5c31\u662fsql\u591a\u8868\u67e5\u8be2\u8bed\u53e5\u600e\u4e48\u5199\u7684\u8be6\u7ec6\u5185\u5bb9\uff0c\u66f4\u591a\u8bf7\u5173\u6ce8\u7c73\u4e91\u7f51\u5176\u5b83\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u591a\u8868\u67e5\u8be2\u8bed\u53e5\u7528\u4e8e\u4ece\u591a\u4e2a\u8868\u4e2d\u83b7\u53d6\u6570\u636e\u3002\u53ef\u4f7f\u7528 join \u5173\u952e\u5b57\u6307\u5b9a\u8868\u5173\u7cfb\uff0c\u5e38\u7528\u7c7b\u578b\u4e3a\uff1ainner join\uff08\u5339\u914d\u884c\uff09\u3001left join\uff08\u5de6\u8868\u5168\u884c\uff0c\u53f3\u8868\u5339\u914d\u884c\u6216 null\uff09\u3001right join\uff08\u53f3\u8868\u5168\u884c\uff0c\u5de6\u8868\u5339\u914d\u884c\u6216 null\uff09\u3001full join\uff08\u4e24\u4e2a\u8868\u5168\u884c\uff09\u3002\u7f16\u5199\u6b65\u9aa4\uff1a\u786e\u5b9a\u8868\u3001\u6307\u5b9a join \u7c7b\u578b\u3001\u6307\u5b9a\u8fde\u63a5\u6761\u4ef6\u3001\u9009\u62e9\u663e\u793a\u5217\u3002 SQL \u591a\u8868\u67e5\u8be2\u8bed\u53e5 \u5982\u4f55\u7f16\u5199\u591a\u8868\u67e5\u8be2\u8bed\u53e5\uff1f \u591a\u8868\u67e5\u8be2\u8bed\u53e5\u7528\u4e8e\u4ece\u591a\u4e2a\u8868\u4e2d\u83b7\u53d6\u6570\u636e\u3002\u8981\u7f16\u5199\u591a\u8868\u67e5\u8be2\uff0c\u53ef\u4ee5\u4f7f\u7528 JOIN \u5173\u952e\u5b57\uff0c\u5b83\u6307\u5b9a\u8868\u4e4b\u95f4\u7684\u5173\u7cfb\u3002 \u5e38\u7528\u7684 JOIN \u7c7b\u578b\uff1a INNER JOIN\uff1a\u4ec5\u8fd4\u56de\u5177\u6709\u5339\u914d\u884c\u7684\u6240\u6709\u884c\u3002 LEFT JOIN\uff1a\u8fd4\u56de\u5de6\u8868\u7684\u5168\u90e8\u884c\uff0c\u4ee5\u53ca\u5339\u914d\u53f3\u8868\u884c\u7684\u53f3\u8868\u884c\u3002\u5982\u679c\u53f3\u8868\u4e2d\u6ca1\u6709\u5339\u914d\u9879\uff0c\u5219\u8fd4\u56de NULL\u3002 RIGHT JOIN\uff1a\u4e0e LEFT JOIN \u76f8\u53cd\uff0c\u8fd4\u56de\u53f3\u8868\u7684\u5168\u90e8\u884c\u4ee5\u53ca\u5339\u914d\u5de6\u8868\u884c\u7684\u5de6\u8868\u884c\u3002 FULL JOIN\uff1a\u8fd4\u56de\u4e24\u4e2a\u8868\u7684\u5168\u90e8\u884c\uff0c\u65e0\u8bba\u662f\u5426\u6709\u5339\u914d\u9879\u3002 \u7f16\u5199\u591a\u8868\u67e5\u8be2\u8bed\u53e5\u7684\u6b65\u9aa4\uff1a \u786e\u5b9a\u8981\u8fde\u63a5\u7684\u8868\uff1a\u786e\u5b9a\u9700\u8981\u4ece\u54ea\u4e9b\u8868\u4e2d\u83b7\u53d6\u6570\u636e\u3002 \u6307\u5b9a JOIN \u7c7b\u578b\uff1a\u6839\u636e\u9700\u8981\u9009\u62e9 INNER JOIN\u3001LEFT JOIN\u3001RIGHT JOIN \u6216 FULL JOIN\u3002 \u6307\u5b9a\u8fde\u63a5\u6761\u4ef6\uff1a\u4f7f\u7528 ON \u5b50\u53e5\u6307\u5b9a\u8868\u4e4b\u95f4\u7684\u5339\u914d\u6761\u4ef6\u3002 \u9009\u62e9\u8981\u663e\u793a\u7684\u5217\uff1a\u4f7f\u7528 SELECT \u5b50\u53e5\u9009\u62e9\u8981\u4ece\u8868\u4e2d\u663e\u793a\u7684\u5217\u3002 \u793a\u4f8b\uff1a \u67e5\u8be2 Customers \u8868\u548c Orders [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[16],"tags":[],"class_list":["post-5638","post","type-post","status-publish","format-standard","hentry","category-16"],"_links":{"self":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/5638","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/comments?post=5638"}],"version-history":[{"count":0,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/posts\/5638\/revisions"}],"wp:attachment":[{"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/media?parent=5638"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/categories?post=5638"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/fwq.ai\/blog\/wp-json\/wp\/v2\/tags?post=5638"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}