{"id":180882,"date":"2024-11-09T13:58:19","date_gmt":"2024-11-09T05:58:19","guid":{"rendered":"https:\/\/server.hk\/cnblog\/180882\/"},"modified":"2024-11-09T13:58:20","modified_gmt":"2024-11-09T05:58:20","slug":"%e6%b7%b1%e5%85%a5%e4%ba%86%e8%a7%a3%e6%95%b8%e6%93%9a%e5%ba%ab-join%e7%9a%84%e5%af%a6%e7%94%a8%e6%8a%80%e5%b7%a7-%e6%95%b8%e6%93%9a%e5%ba%ab-join%e7%9a%84%e7%94%a8%e6%b3%95","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/180882\/","title":{"rendered":"\u6df1\u5165\u4e86\u89e3\u6578\u64da\u5eab join\u7684\u5be6\u7528\u6280\u5de7 (\u6578\u64da\u5eab join\u7684\u7528\u6cd5)"},"content":{"rendered":"<h1 id=\"%e6%b7%b1%e5%85%a5%e4%ba%86%e8%a7%a3%e6%95%b8%e6%93%9a%e5%ba%ab-join-%e7%9a%84%e5%af%a6%e7%94%a8%e6%8a%80%e5%b7%a7-byqhIQESBM\">\u6df1\u5165\u4e86\u89e3\u6578\u64da\u5eab JOIN \u7684\u5be6\u7528\u6280\u5de7<\/h1>\n<p>\u5728\u6578\u64da\u5eab\u7ba1\u7406\u7cfb\u7d71\u4e2d\uff0cJOIN \u662f\u4e00\u500b\u975e\u5e38\u91cd\u8981\u7684\u6982\u5ff5\uff0c\u5b83\u5141\u8a31\u7528\u6236\u5f9e\u591a\u500b\u8868\u4e2d\u6aa2\u7d22\u6578\u64da\u3002\u900f\u904e JOIN\uff0c\u958b\u767c\u8005\u53ef\u4ee5\u5c07\u4e0d\u540c\u8868\u4e2d\u7684\u6578\u64da\u7d50\u5408\u8d77\u4f86\uff0c\u5f9e\u800c\u7372\u5f97\u66f4\u5168\u9762\u7684\u4fe1\u606f\u3002\u672c\u6587\u5c07\u6df1\u5165\u63a2\u8a0e\u6578\u64da\u5eab JOIN \u7684\u7528\u6cd5\u53ca\u5176\u5be6\u7528\u6280\u5de7\uff0c\u5e6b\u52a9\u8b80\u8005\u66f4\u597d\u5730\u7406\u89e3\u548c\u61c9\u7528\u9019\u4e00\u6280\u8853\u3002<\/p>\n<h2 id=\"%e4%bb%80%e9%ba%bc%e6%98%af-join%ef%bc%9f-byqhIQESBM\">\u4ec0\u9ebc\u662f JOIN\uff1f<\/h2>\n<p>JOIN \u662f SQL \u8a9e\u8a00\u4e2d\u7684\u4e00\u500b\u64cd\u4f5c\uff0c\u7528\u65bc\u6839\u64da\u67d0\u4e9b\u689d\u4ef6\u5c07\u5169\u500b\u6216\u591a\u500b\u8868\u4e2d\u7684\u884c\u7d50\u5408\u5728\u4e00\u8d77\u3002\u9019\u4e9b\u689d\u4ef6\u901a\u5e38\u662f\u57fa\u65bc\u8868\u4e4b\u9593\u7684\u95dc\u806f\uff0c\u4f8b\u5982\u4e3b\u9375\u548c\u5916\u9375\u7684\u95dc\u4fc2\u3002JOIN \u7684\u4e3b\u8981\u985e\u578b\u5305\u62ec\uff1a<\/p>\n<ul>\n<li><strong>INNER JOIN<\/strong><\/li>\n<li><strong>LEFT JOIN<\/strong> (\u6216 LEFT OUTER JOIN)<\/li>\n<li><strong>RIGHT JOIN<\/strong> (\u6216 RIGHT OUTER JOIN)<\/li>\n<li><strong>FULL JOIN<\/strong> (\u6216 FULL OUTER JOIN)<\/li>\n<li><strong>CROSS JOIN<\/strong><\/li>\n<\/ul>\n<h2 id=\"join-%e7%9a%84%e9%a1%9e%e5%9e%8b%e5%8f%8a%e5%85%b6%e7%94%a8%e6%b3%95-byqhIQESBM\">JOIN \u7684\u985e\u578b\u53ca\u5176\u7528\u6cd5<\/h2>\n<h3 id=\"1-inner-join-byqhIQESBM\">1. INNER JOIN<\/h3>\n<p>INNER JOIN \u662f\u6700\u5e38\u7528\u7684 JOIN \u985e\u578b\uff0c\u5b83\u53ea\u8fd4\u56de\u5169\u500b\u8868\u4e2d\u5339\u914d\u7684\u884c\u3002\u4ee5\u4e0b\u662f\u4e00\u500b\u793a\u4f8b\uff1a<\/p>\n<pre><code>SELECT a.name, b.salary\nFROM employees a\nINNER JOIN salaries b ON a.id = b.employee_id;<\/code><\/pre>\n<p>\u5728\u9019\u500b\u4f8b\u5b50\u4e2d\uff0c\u53ea\u6709\u7576\u54e1\u5de5\u8868\u548c\u85aa\u8cc7\u8868\u4e2d\u6709\u5339\u914d\u7684\u54e1\u5de5 ID \u6642\uff0c\u624d\u6703\u8fd4\u56de\u7d50\u679c\u3002<\/p>\n<h3 id=\"2-left-join-byqhIQESBM\">2. LEFT JOIN<\/h3>\n<p>LEFT JOIN \u8fd4\u56de\u5de6\u5074\u8868\u4e2d\u7684\u6240\u6709\u884c\uff0c\u5373\u4f7f\u53f3\u5074\u8868\u4e2d\u6c92\u6709\u5339\u914d\u7684\u884c\u3002\u672a\u5339\u914d\u7684\u884c\u5c07\u986f\u793a\u70ba NULL\u3002\u793a\u4f8b\uff1a<\/p>\n<pre><code>SELECT a.name, b.salary\nFROM employees a\nLEFT JOIN salaries b ON a.id = b.employee_id;<\/code><\/pre>\n<p>\u9019\u6a23\uff0c\u5373\u4f7f\u67d0\u4e9b\u54e1\u5de5\u6c92\u6709\u85aa\u8cc7\u8a18\u9304\uff0c\u4ed6\u5011\u7684\u540d\u5b57\u4ecd\u7136\u6703\u986f\u793a\u51fa\u4f86\u3002<\/p>\n<h3 id=\"3-right-join-byqhIQESBM\">3. RIGHT JOIN<\/h3>\n<p>RIGHT JOIN \u8207 LEFT JOIN \u76f8\u53cd\uff0c\u5b83\u8fd4\u56de\u53f3\u5074\u8868\u4e2d\u7684\u6240\u6709\u884c\u3002\u793a\u4f8b\uff1a<\/p>\n<pre><code>SELECT a.name, b.salary\nFROM employees a\nRIGHT JOIN salaries b ON a.id = b.employee_id;<\/code><\/pre>\n<p>\u9019\u6a23\uff0c\u5373\u4f7f\u67d0\u4e9b\u85aa\u8cc7\u8a18\u9304\u6c92\u6709\u5c0d\u61c9\u7684\u54e1\u5de5\uff0c\u85aa\u8cc7\u4ecd\u7136\u6703\u986f\u793a\u51fa\u4f86\u3002<\/p>\n<h3 id=\"4-full-join-byqhIQESBM\">4. FULL JOIN<\/h3>\n<p>FULL JOIN \u8fd4\u56de\u5169\u500b\u8868\u4e2d\u7684\u6240\u6709\u884c\uff0c\u7121\u8ad6\u662f\u5426\u6709\u5339\u914d\u3002\u793a\u4f8b\uff1a<\/p>\n<pre><code>SELECT a.name, b.salary\nFROM employees a\nFULL JOIN salaries b ON a.id = b.employee_id;<\/code><\/pre>\n<p>\u9019\u6a23\u53ef\u4ee5\u7372\u5f97\u6240\u6709\u54e1\u5de5\u548c\u85aa\u8cc7\u7684\u5b8c\u6574\u5217\u8868\u3002<\/p>\n<h3 id=\"5-cross-join-byqhIQESBM\">5. CROSS JOIN<\/h3>\n<p>CROSS JOIN \u8fd4\u56de\u5169\u500b\u8868\u7684\u7b1b\u5361\u723e\u7a4d\uff0c\u5373\u6bcf\u500b\u884c\u8207\u53e6\u4e00\u500b\u8868\u7684\u6bcf\u500b\u884c\u90fd\u6703\u7d44\u5408\u3002\u793a\u4f8b\uff1a<\/p>\n<pre><code>SELECT a.name, b.department\nFROM employees a\nCROSS JOIN departments b;<\/code><\/pre>\n<p>\u9019\u6a23\u6703\u8fd4\u56de\u6bcf\u4f4d\u54e1\u5de5\u8207\u6bcf\u500b\u90e8\u9580\u7684\u7d44\u5408\u3002<\/p>\n<h2 id=\"join-%e7%9a%84%e5%af%a6%e7%94%a8%e6%8a%80%e5%b7%a7-byqhIQESBM\">JOIN \u7684\u5be6\u7528\u6280\u5de7<\/h2>\n<ul>\n<li><strong>\u4f7f\u7528\u5225\u540d\uff1a<\/strong>\u5728\u67e5\u8a62\u4e2d\u4f7f\u7528\u8868\u7684\u5225\u540d\u53ef\u4ee5\u63d0\u9ad8\u53ef\u8b80\u6027\uff0c\u7279\u5225\u662f\u5728\u6d89\u53ca\u591a\u500b\u8868\u7684\u60c5\u6cc1\u4e0b\u3002<\/li>\n<li><strong>\u907f\u514d\u4f7f\u7528 SELECT *\uff1a<\/strong>\u660e\u78ba\u6307\u5b9a\u9700\u8981\u7684\u5217\u53ef\u4ee5\u63d0\u9ad8\u67e5\u8a62\u6027\u80fd\uff0c\u4e26\u6e1b\u5c11\u4e0d\u5fc5\u8981\u7684\u6578\u64da\u50b3\u8f38\u3002<\/li>\n<li><strong>\u7d22\u5f15\u7684\u4f7f\u7528\uff1a<\/strong>\u5728 JOIN \u7684\u5217\u4e0a\u5275\u5efa\u7d22\u5f15\u53ef\u4ee5\u986f\u8457\u63d0\u9ad8\u67e5\u8a62\u6027\u80fd\u3002<\/li>\n<li><strong>\u7406\u89e3\u6578\u64da\u95dc\u806f\uff1a<\/strong>\u5728\u8a2d\u8a08\u6578\u64da\u5eab\u6642\uff0c\u6e05\u695a\u4e86\u89e3\u8868\u4e4b\u9593\u7684\u95dc\u806f\u6027\u6709\u52a9\u65bc\u66f4\u6709\u6548\u5730\u4f7f\u7528 JOIN\u3002<\/li>\n<\/ul>\n<h2 id=\"%e7%b8%bd%e7%b5%90-byqhIQESBM\">\u7e3d\u7d50<\/h2>\n<p>\u6578\u64da\u5eab JOIN \u662f\u4e00\u500b\u5f37\u5927\u7684\u5de5\u5177\uff0c\u80fd\u5920\u5e6b\u52a9\u958b\u767c\u8005\u5f9e\u591a\u500b\u8868\u4e2d\u63d0\u53d6\u548c\u7d44\u5408\u6578\u64da\u3002\u901a\u904e\u638c\u63e1\u4e0d\u540c\u985e\u578b\u7684 JOIN \u53ca\u5176\u7528\u6cd5\uff0c\u958b\u767c\u8005\u53ef\u4ee5\u66f4\u9748\u6d3b\u5730\u8655\u7406\u6578\u64da\uff0c\u63d0\u5347\u61c9\u7528\u7a0b\u5e8f\u7684\u6027\u80fd\u548c\u53ef\u7528\u6027\u3002\u82e5\u60a8\u9700\u8981\u9ad8\u6548\u7684\u6578\u64da\u5eab\u89e3\u6c7a\u65b9\u6848\uff0c\u8003\u616e\u4f7f\u7528 <a href=\"https:\/\/server.hk\">\u9999\u6e2f VPS<\/a> \u670d\u52d9\uff0c\u9019\u5c07\u70ba\u60a8\u7684\u6578\u64da\u7ba1\u7406\u63d0\u4f9b\u7a69\u5b9a\u7684\u652f\u6301\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u63a2\u7d22\u6578\u64da\u5eab join \u7684\u5be6\u7528\u6280\u5de7\uff0c\u5b78\u7fd2\u5982\u4f55\u6709\u6548\u5730\u7d50\u5408\u6578\u64da\uff0c\u63d0\u5347\u67e5\u8a62\u6548\u7387\uff0c\u512a\u5316\u6578\u64da\u7ba1\u7406\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-180882","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/180882","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=180882"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/180882\/revisions"}],"predecessor-version":[{"id":180883,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/180882\/revisions\/180883"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=180882"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=180882"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=180882"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}