{"id":74573,"date":"2024-10-15T22:35:19","date_gmt":"2024-10-15T14:35:19","guid":{"rendered":"https:\/\/server.hk\/cnblog\/74573\/"},"modified":"2024-10-15T22:35:19","modified_gmt":"2024-10-15T14:35:19","slug":"mysql-left-join-right-join%e7%9a%84%e5%8d%80%e5%88%a5","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/74573\/","title":{"rendered":"MySQL LEFT JOIN, RIGHT JOIN\u7684\u5340\u5225"},"content":{"rendered":"<h1 id=\"mysql-left-join-%e8%88%87-right-join-%e7%9a%84%e5%8d%80%e5%88%a5-uVtewkJbla\">MySQL LEFT JOIN \u8207 RIGHT JOIN \u7684\u5340\u5225<\/h1>\n<p>\u5728\u8cc7\u6599\u5eab\u7ba1\u7406\u7cfb\u7d71\u4e2d\uff0cMySQL \u662f\u4e00\u500b\u5ee3\u6cdb\u4f7f\u7528\u7684\u95dc\u806f\u5f0f\u8cc7\u6599\u5eab\u7cfb\u7d71\u3002\u7576\u6211\u5011\u9700\u8981\u5f9e\u591a\u500b\u8cc7\u6599\u8868\u4e2d\u63d0\u53d6\u8cc7\u6599\u6642\uff0cJOIN \u64cd\u4f5c\u662f\u4e0d\u53ef\u6216\u7f3a\u7684\u3002\u7279\u5225\u662f LEFT JOIN \u548c RIGHT JOIN\uff0c\u9019\u5169\u7a2e JOIN \u985e\u578b\u5728\u8cc7\u6599\u67e5\u8a62\u4e2d\u626e\u6f14\u8457\u91cd\u8981\u7684\u89d2\u8272\u3002\u672c\u6587\u5c07\u6df1\u5165\u63a2\u8a0e\u9019\u5169\u8005\u7684\u5340\u5225\u53ca\u5176\u4f7f\u7528\u60c5\u5883\u3002<\/p>\n<h2 id=\"%e4%bb%80%e9%ba%bc%e6%98%af-join%ef%bc%9f-uVtewkJbla\">\u4ec0\u9ebc\u662f JOIN\uff1f<\/h2>\n<p>JOIN \u662f\u4e00\u7a2e SQL \u64cd\u4f5c\uff0c\u7528\u65bc\u5c07\u4f86\u81ea\u5169\u500b\u6216\u591a\u500b\u8cc7\u6599\u8868\u7684\u8cc7\u6599\u6839\u64da\u67d0\u4e9b\u689d\u4ef6\u7d50\u5408\u5728\u4e00\u8d77\u3002\u9019\u4f7f\u5f97\u7528\u6236\u80fd\u5920\u5f9e\u4e0d\u540c\u7684\u8cc7\u6599\u8868\u4e2d\u7372\u53d6\u76f8\u95dc\u7684\u8cc7\u8a0a\u3002JOIN \u7684\u985e\u578b\u6709\u5f88\u591a\uff0c\u5176\u4e2d\u6700\u5e38\u898b\u7684\u5305\u62ec INNER JOIN\u3001LEFT JOIN \u548c RIGHT JOIN\u3002<\/p>\n<h2 id=\"left-join-%e7%9a%84%e5%ae%9a%e7%be%a9-uVtewkJbla\">LEFT JOIN \u7684\u5b9a\u7fa9<\/h2>\n<p>LEFT JOIN\uff08\u6216\u7a31\u70ba LEFT OUTER JOIN\uff09\u662f\u5f9e\u5de6\u5074\u8cc7\u6599\u8868\u4e2d\u9078\u53d6\u6240\u6709\u7684\u8a18\u9304\uff0c\u4e26\u4e14\u5f9e\u53f3\u5074\u8cc7\u6599\u8868\u4e2d\u9078\u53d6\u7b26\u5408\u689d\u4ef6\u7684\u8a18\u9304\u3002\u5982\u679c\u53f3\u5074\u8cc7\u6599\u8868\u4e2d\u6c92\u6709\u7b26\u5408\u7684\u8a18\u9304\uff0c\u5247\u7d50\u679c\u4e2d\u6703\u986f\u793a NULL \u503c\u3002<\/p>\n<h3 id=\"left-join-%e7%9a%84%e8%aa%9e%e6%b3%95-uVtewkJbla\">LEFT JOIN \u7684\u8a9e\u6cd5<\/h3>\n<pre><code>SELECT A.column1, B.column2\nFROM TableA A\nLEFT JOIN TableB B ON A.common_column = B.common_column;<\/code><\/pre>\n<h3 id=\"left-join-%e7%9a%84%e7%af%84%e4%be%8b-uVtewkJbla\">LEFT JOIN \u7684\u7bc4\u4f8b<\/h3>\n<p>\u5047\u8a2d\u6709\u5169\u500b\u8cc7\u6599\u8868\uff1a<strong>Customers<\/strong> \u548c <strong>Orders<\/strong>\u3002<\/p>\n<ul>\n<li><strong>Customers<\/strong> \u8868\u5305\u542b\u5ba2\u6236\u7684\u8cc7\u8a0a\uff1a<\/li>\n<ul>\n<li>CustomerID<\/li>\n<li>Name<\/li>\n<\/ul>\n<li><strong>Orders<\/strong> \u8868\u5305\u542b\u8a02\u55ae\u7684\u8cc7\u8a0a\uff1a<\/li>\n<ul>\n<li>OrderID<\/li>\n<li>CustomerID<\/li>\n<li>OrderDate<\/li>\n<\/ul>\n<\/ul>\n<p>\u4f7f\u7528 LEFT JOIN \u67e5\u8a62\u6240\u6709\u5ba2\u6236\u53ca\u5176\u8a02\u55ae\uff1a<\/p>\n<pre><code>SELECT Customers.Name, Orders.OrderDate\nFROM Customers\nLEFT JOIN Orders ON Customers.CustomerID = Orders.CustomerID;<\/code><\/pre>\n<p>\u9019\u6a23\u7684\u67e5\u8a62\u5c07\u8fd4\u56de\u6240\u6709\u5ba2\u6236\u7684\u540d\u7a31\uff0c\u5373\u4f7f\u67d0\u4e9b\u5ba2\u6236\u6c92\u6709\u8a02\u55ae\uff0c\u5c0d\u61c9\u7684\u8a02\u55ae\u65e5\u671f\u5c07\u986f\u793a\u70ba NULL\u3002<\/p>\n<h2 id=\"right-join-%e7%9a%84%e5%ae%9a%e7%be%a9-uVtewkJbla\">RIGHT JOIN \u7684\u5b9a\u7fa9<\/h2>\n<p>RIGHT JOIN\uff08\u6216\u7a31\u70ba RIGHT OUTER JOIN\uff09\u5247\u662f\u5f9e\u53f3\u5074\u8cc7\u6599\u8868\u4e2d\u9078\u53d6\u6240\u6709\u7684\u8a18\u9304\uff0c\u4e26\u4e14\u5f9e\u5de6\u5074\u8cc7\u6599\u8868\u4e2d\u9078\u53d6\u7b26\u5408\u689d\u4ef6\u7684\u8a18\u9304\u3002\u5982\u679c\u5de6\u5074\u8cc7\u6599\u8868\u4e2d\u6c92\u6709\u7b26\u5408\u7684\u8a18\u9304\uff0c\u5247\u7d50\u679c\u4e2d\u6703\u986f\u793a NULL \u503c\u3002<\/p>\n<h3 id=\"right-join-%e7%9a%84%e8%aa%9e%e6%b3%95-uVtewkJbla\">RIGHT JOIN \u7684\u8a9e\u6cd5<\/h3>\n<pre><code>SELECT A.column1, B.column2\nFROM TableA A\nRIGHT JOIN TableB B ON A.common_column = B.common_column;<\/code><\/pre>\n<h3 id=\"right-join-%e7%9a%84%e7%af%84%e4%be%8b-uVtewkJbla\">RIGHT JOIN \u7684\u7bc4\u4f8b<\/h3>\n<p>\u5ef6\u7e8c\u4e0a\u9762\u7684\u4f8b\u5b50\uff0c\u4f7f\u7528 RIGHT JOIN \u67e5\u8a62\u6240\u6709\u8a02\u55ae\u53ca\u5176\u5ba2\u6236\uff1a<\/p>\n<pre><code>SELECT Customers.Name, Orders.OrderDate\nFROM Customers\nRIGHT JOIN Orders ON Customers.CustomerID = Orders.CustomerID;<\/code><\/pre>\n<p>\u9019\u6a23\u7684\u67e5\u8a62\u5c07\u8fd4\u56de\u6240\u6709\u8a02\u55ae\u7684\u65e5\u671f\uff0c\u5373\u4f7f\u67d0\u4e9b\u8a02\u55ae\u6c92\u6709\u5c0d\u61c9\u7684\u5ba2\u6236\uff0c\u5c0d\u61c9\u7684\u5ba2\u6236\u540d\u7a31\u5c07\u986f\u793a\u70ba NULL\u3002<\/p>\n<h2 id=\"left-join-%e8%88%87-right-join-%e7%9a%84%e5%8d%80%e5%88%a5-uVtewkJbla\">LEFT JOIN \u8207 RIGHT JOIN \u7684\u5340\u5225<\/h2>\n<p>\u7e3d\u7d50\u4f86\u8aaa\uff0cLEFT JOIN \u548c RIGHT JOIN \u7684\u4e3b\u8981\u5340\u5225\u5728\u65bc\u5b83\u5011\u6240\u9078\u53d6\u7684\u8cc7\u6599\u8868\u3002LEFT JOIN \u6703\u4fdd\u7559\u5de6\u5074\u8cc7\u6599\u8868\u7684\u6240\u6709\u8a18\u9304\uff0c\u800c RIGHT JOIN \u5247\u6703\u4fdd\u7559\u53f3\u5074\u8cc7\u6599\u8868\u7684\u6240\u6709\u8a18\u9304\u3002\u9019\u4f7f\u5f97\u5728\u4e0d\u540c\u7684\u60c5\u5883\u4e0b\uff0c\u9078\u64c7\u5408\u9069\u7684 JOIN \u985e\u578b\u81f3\u95dc\u91cd\u8981\u3002<\/p>\n<h2 id=\"%e7%b5%90%e8%ab%96-uVtewkJbla\">\u7d50\u8ad6<\/h2>\n<p>\u5728\u4f7f\u7528 MySQL \u9032\u884c\u8cc7\u6599\u67e5\u8a62\u6642\uff0c\u4e86\u89e3 LEFT JOIN \u548c RIGHT JOIN \u7684\u5340\u5225\u662f\u975e\u5e38\u91cd\u8981\u7684\u3002\u6839\u64da\u9700\u6c42\u9078\u64c7\u5408\u9069\u7684 JOIN \u985e\u578b\uff0c\u53ef\u4ee5\u6709\u6548\u5730\u7372\u53d6\u6240\u9700\u7684\u8cc7\u6599\u3002\u7121\u8ad6\u662f\u9032\u884c\u8cc7\u6599\u5206\u6790\u9084\u662f\u958b\u767c\u61c9\u7528\u7a0b\u5f0f\uff0c\u638c\u63e1\u9019\u4e9b\u57fa\u672c\u6982\u5ff5\u90fd\u80fd\u5e6b\u52a9\u958b\u767c\u8005\u66f4\u9ad8\u6548\u5730\u5de5\u4f5c\u3002<\/p>\n<p>\u5982\u9700\u9032\u4e00\u6b65\u4e86\u89e3 MySQL \u6216\u5176\u4ed6\u8cc7\u6599\u5eab\u6280\u8853\uff0c\u60a8\u53ef\u4ee5\u8003\u616e\u4f7f\u7528 <a href=\"https:\/\/server.hk\">\u9999\u6e2f VPS<\/a> \u670d\u52d9\uff0c\u9019\u5c07\u70ba\u60a8\u7684\u958b\u767c\u74b0\u5883\u63d0\u4f9b\u7a69\u5b9a\u7684\u652f\u6301\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4e86\u89e3MySQL\u4e2dLEFT JOIN\u548cRIGHT JOIN\u7684\u5340\u5225\uff0c\u638c\u63e1\u5982\u4f55\u6709\u6548\u5730\u5f9e\u591a\u500b\u8868\u4e2d\u63d0\u53d6\u6578\u64da\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-74573","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/74573","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=74573"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/74573\/revisions"}],"predecessor-version":[{"id":74574,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/74573\/revisions\/74574"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=74573"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=74573"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=74573"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}