{"id":217777,"date":"2023-12-23T00:05:22","date_gmt":"2023-12-22T16:05:22","guid":{"rendered":"https:\/\/www.idc.net\/help\/217777\/"},"modified":"2023-12-23T00:05:22","modified_gmt":"2023-12-22T16:05:22","slug":"mysql%e4%bd%bf%e7%94%a8%e6%89%8b%e5%86%8c%ef%bc%9a%e4%bd%bf%e7%94%a8left-join%e5%85%b3%e9%94%ae%e5%ad%97%e8%bf%94%e5%9b%9e%e5%b7%a6%e8%a1%a8%e7%9a%84%e6%89%80%e6%9c%89%e8%ae%b0%e5%bd%95%e4%bb%a5","status":"publish","type":"post","link":"https:\/\/idc.net\/help\/217777\/","title":{"rendered":"MySQL\u4f7f\u7528\u624b\u518c\uff1a\u4f7f\u7528LEFT JOIN\u5173\u952e\u5b57\u8fd4\u56de\u5de6\u8868\u7684\u6240\u6709\u8bb0\u5f55\u4ee5\u53ca\u53f3\u8868\u7684\u5339\u914d\u8bb0\u5f55"},"content":{"rendered":"<p><title id=\"mysql%e4%bd%bf%e7%94%a8%e6%89%8b%e5%86%8c%ef%bc%9a%e4%bd%bf%e7%94%a8left-join%e5%85%b3%e9%94%ae%e5%ad%97%e8%bf%94%e5%9b%9e%e5%b7%a6%e8%a1%a8%e7%9a%84%e6%89%80%e6%9c%89%e8%ae%b0%e5%bd%95%e4%bb%a5-kjixyMpOaq\">MySQL\u4f7f\u7528\u624b\u518c\uff1a\u4f7f\u7528LEFT JOIN\u5173\u952e\u5b57\u8fd4\u56de\u5de6\u8868\u7684\u6240\u6709\u8bb0\u5f55\u4ee5\u53ca\u53f3\u8868\u7684\u5339\u914d\u8bb0\u5f55<\/title><\/p>\n<h1 id=\"mysql%e4%bd%bf%e7%94%a8%e6%89%8b%e5%86%8c%ef%bc%9a%e4%bd%bf%e7%94%a8left-join%e5%85%b3%e9%94%ae%e5%ad%97%e8%bf%94%e5%9b%9e%e5%b7%a6%e8%a1%a8%e7%9a%84%e6%89%80%e6%9c%89%e8%ae%b0%e5%bd%95%e4%bb%a5-kjixyMpOaq\">MySQL\u4f7f\u7528\u624b\u518c\uff1a\u4f7f\u7528LEFT JOIN\u5173\u952e\u5b57\u8fd4\u56de\u5de6\u8868\u7684\u6240\u6709\u8bb0\u5f55\u4ee5\u53ca\u53f3\u8868\u7684\u5339\u914d\u8bb0\u5f55<\/h1>\n<p>\u5728MySQL\u4e2d\uff0c\u4f7f\u7528LEFT JOIN\u5173\u952e\u5b57\u53ef\u4ee5\u8fd4\u56de\u5de6\u8868\u7684\u6240\u6709\u8bb0\u5f55\u4ee5\u53ca\u53f3\u8868\u7684\u5339\u914d\u8bb0\u5f55\u3002LEFT JOIN\u662f\u4e00\u79cd\u8fde\u63a5\u64cd\u4f5c\uff0c\u5b83\u5c06\u5de6\u8868\u4e2d\u7684\u6240\u6709\u8bb0\u5f55\u4e0e\u53f3\u8868\u4e2d\u7684\u5339\u914d\u8bb0\u5f55\u8fdb\u884c\u8fde\u63a5\uff0c\u5982\u679c\u53f3\u8868\u4e2d\u6ca1\u6709\u5339\u914d\u8bb0\u5f55\uff0c\u5219\u8fd4\u56deNULL\u503c\u3002<\/p>\n<p>LEFT JOIN\u7684\u8bed\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre><code>SELECT column_name(s)\nFROM table1\nLEFT JOIN table2\nON table1.column_name = table2.column_name;<\/code><\/pre>\n<p>\u5728\u8fd9\u4e2a\u8bed\u6cd5\u4e2d\uff0ctable1\u662f\u5de6\u8868\uff0ctable2\u662f\u53f3\u8868\uff0ccolumn_name\u662f\u8fde\u63a5\u7684\u5217\u540d\u3002<\/p>\n<p>\u4e0b\u9762\u662f\u4e00\u4e2a\u793a\u4f8b\uff0c\u5047\u8bbe\u6211\u4eec\u6709\u4e24\u4e2a\u8868\uff1a\u5b66\u751f\u8868\u548c\u6210\u7ee9\u8868\u3002<\/p>\n<p>\u5b66\u751f\u8868\uff08students\uff09\u5305\u542b\u4ee5\u4e0b\u5217\uff1a\u5b66\u751fID\uff08student_id\uff09\u3001\u59d3\u540d\uff08name\uff09\u548c\u5e74\u9f84\uff08age\uff09\u3002<\/p>\n<p>\u6210\u7ee9\u8868\uff08scores\uff09\u5305\u542b\u4ee5\u4e0b\u5217\uff1a\u5b66\u751fID\uff08student_id\uff09\u548c\u5206\u6570\uff08score\uff09\u3002<\/p>\n<p>\u6211\u4eec\u60f3\u8981\u67e5\u8be2\u6bcf\u4e2a\u5b66\u751f\u7684\u59d3\u540d\u548c\u5206\u6570\uff0c\u5373\u4f7f\u4ed6\u4eec\u6ca1\u6709\u6210\u7ee9\u8bb0\u5f55\u3002<\/p>\n<pre><code>SELECT students.name, scores.score\nFROM students\nLEFT JOIN scores\nON students.student_id = scores.student_id;<\/code><\/pre>\n<p>\u5728\u8fd9\u4e2a\u4f8b\u5b50\u4e2d\uff0cLEFT JOIN\u5c06\u8fd4\u56de\u5b66\u751f\u8868\u4e2d\u7684\u6240\u6709\u8bb0\u5f55\uff0c\u4ee5\u53ca\u4e0e\u4e4b\u5339\u914d\u7684\u6210\u7ee9\u8868\u4e2d\u7684\u8bb0\u5f55\u3002\u5982\u679c\u5b66\u751f\u6ca1\u6709\u6210\u7ee9\u8bb0\u5f55\uff0c\u90a3\u4e48\u5206\u6570\u5217\u5c06\u663e\u793a\u4e3aNULL\u3002<\/p>\n<p>\u4f7f\u7528LEFT JOIN\u53ef\u4ee5\u5e2e\u52a9\u6211\u4eec\u5904\u7406\u7f3a\u5931\u6570\u636e\u7684\u60c5\u51b5\u3002\u4f8b\u5982\uff0c\u5982\u679c\u6211\u4eec\u60f3\u8981\u67e5\u8be2\u6bcf\u4e2a\u5b66\u751f\u7684\u59d3\u540d\u548c\u5206\u6570\uff0c\u5e76\u4e14\u53ea\u663e\u793a\u6709\u6210\u7ee9\u8bb0\u5f55\u7684\u5b66\u751f\uff0c\u53ef\u4ee5\u4f7f\u7528INNER JOIN\u5173\u952e\u5b57\u3002<\/p>\n<pre><code>SELECT students.name, scores.score\nFROM students\nINNER JOIN scores\nON students.student_id = scores.student_id;<\/code><\/pre>\n<p>\u5728\u8fd9\u4e2a\u4f8b\u5b50\u4e2d\uff0cINNER JOIN\u53ea\u8fd4\u56de\u5b66\u751f\u8868\u548c\u6210\u7ee9\u8868\u4e2d\u6709\u5339\u914d\u8bb0\u5f55\u7684\u5b66\u751f\u3002<\/p>\n<p>\u603b\u7ed3\uff1a<\/p>\n<p>\u901a\u8fc7\u4f7f\u7528LEFT JOIN\u5173\u952e\u5b57\uff0c\u6211\u4eec\u53ef\u4ee5\u8fd4\u56de\u5de6\u8868\u7684\u6240\u6709\u8bb0\u5f55\u4ee5\u53ca\u53f3\u8868\u7684\u5339\u914d\u8bb0\u5f55\u3002\u8fd9\u5bf9\u4e8e\u5904\u7406\u7f3a\u5931\u6570\u636e\u7684\u60c5\u51b5\u975e\u5e38\u6709\u7528\u3002\u5982\u679c\u60a8\u60f3\u8981\u67e5\u8be2\u6bcf\u4e2a\u5b66\u751f\u7684\u59d3\u540d\u548c\u5206\u6570\uff0c\u5e76\u4e14\u53ea\u663e\u793a\u6709\u6210\u7ee9\u8bb0\u5f55\u7684\u5b66\u751f\uff0c\u53ef\u4ee5\u4f7f\u7528INNER JOIN\u5173\u952e\u5b57\u3002<\/p>\n<p>\u9999\u6e2f\u670d\u52a1\u5668\u9996\u9009\u540e\u6d6a\u4e91\uff1a<a href=\"https:\/\/idc.net\">https:\/\/idc.net<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>MySQL\u4f7f\u7528\u624b\u518c\uff1a\u4f7f\u7528LEFT JOIN\u5173\u952e\u5b57\u8fd4\u56de\u5de6\u8868\u7684\u6240\u6709\u8bb0\u5f55\u4ee5\u53ca\u53f3\u8868\u7684\u5339\u914d\u8bb0\u5f55 MySQL\u4f7f\u7528\u624b\u518c\uff1a\u4f7f\u7528 [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[197851],"tags":[],"class_list":["post-217777","post","type-post","status-publish","format-standard","hentry","category-php"],"_links":{"self":[{"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/posts\/217777","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/comments?post=217777"}],"version-history":[{"count":0,"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/posts\/217777\/revisions"}],"wp:attachment":[{"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/media?parent=217777"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/categories?post=217777"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/idc.net\/help\/wp-json\/wp\/v2\/tags?post=217777"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}