{"id":237,"date":"2023-02-24T05:58:09","date_gmt":"2023-02-23T21:58:09","guid":{"rendered":"https:\/\/www.appblog.cn\/?p=237"},"modified":"2023-04-30T15:21:14","modified_gmt":"2023-04-30T07:21:14","slug":"mysql-join-connection-usage","status":"publish","type":"post","link":"https:\/\/www.appblog.cn\/index.php\/2023\/02\/24\/mysql-join-connection-usage\/","title":{"rendered":"MySQL JOIN\u8fde\u63a5\u7684\u4f7f\u7528"},"content":{"rendered":"<p>\u4f7f\u7528 MySQL \u7684 JOIN \u5728\u4e24\u4e2a\u6216\u591a\u4e2a\u8868\u4e2d\u67e5\u8be2\u6570\u636e\u3002\u53ef\u4ee5\u5728 SELECT, UPDATE \u548c DELETE \u8bed\u53e5\u4e2d\u4f7f\u7528 Mysql \u7684 JOIN \u6765\u8054\u5408\u591a\u8868\u67e5\u8be2\u3002<\/p>\n<p>JOIN \u6309\u7167\u529f\u80fd\u5927\u81f4\u5206\u4e3a\u5982\u4e0b\u4e09\u7c7b\uff1a<\/p>\n<ul>\n<li><code>INNER JOIN<\/code>\uff08\u5185\u8fde\u63a5\uff0c\u6216\u7b49\u503c\u8fde\u63a5\uff09\uff1a\u83b7\u53d6\u4e24\u4e2a\u8868\u4e2d\u5b57\u6bb5\u5339\u914d\u5173\u7cfb\u7684\u8bb0\u5f55<\/li>\n<li><code>LEFT JOIN<\/code>\uff08\u5de6\u8fde\u63a5\uff09\uff1a\u83b7\u53d6\u5de6\u8868\u6240\u6709\u8bb0\u5f55\uff0c\u5373\u4f7f\u53f3\u8868\u6ca1\u6709\u5bf9\u5e94\u5339\u914d\u7684\u8bb0\u5f55<\/li>\n<li><code>RIGHT JOIN<\/code>\uff08\u53f3\u8fde\u63a5\uff09\uff1a\u4e0e<code>LEFT JOIN<\/code>\u76f8\u53cd\uff0c\u7528\u4e8e\u83b7\u53d6\u53f3\u8868\u6240\u6709\u8bb0\u5f55\uff0c\u5373\u4f7f\u5de6\u8868\u6ca1\u6709\u5bf9\u5e94\u5339\u914d\u7684\u8bb0\u5f55<\/li>\n<\/ul>\n<p><!-- more --><\/p>\n<h2>MySQL INNER JOIN<\/h2>\n<p>\u6211\u4eec\u5728appblog\u6570\u636e\u5e93\u4e2d\u6709\u4e24\u5f20\u8868<code>tcount_tbl<\/code>\u548c<code>appblog_tbl<\/code><\/p>\n<pre><code class=\"language-sql\">mysql&gt; use appblog;\nDatabase changed\nmysql&gt; SELECT * FROM tcount_tbl;\n+-----------------+--------------+\n| appblog_author  | appblog_count|\n+-----------------+--------------+\n| APP\u5f00\u53d1\u6280\u672f\u535a\u5ba2 | 10           |\n| APPBLOG.CN      | 20           |\n| Google          | 22           |\n+-----------------+--------------+\n3 rows in set (0.01 sec)\n\nmysql&gt; SELECT * from appblog_tbl;\n+------------+---------------+-----------------+-----------------+\n| appblog_id | appblog_title | appblog_author  | submission_date |\n+------------+---------------+-----------------+-----------------+\n| 1          | \u5b66\u4e60 PHP      | APP\u5f00\u53d1\u6280\u672f\u535a\u5ba2 | 2017-04-12      |\n| 2          | \u5b66\u4e60 MySQL    | APP\u5f00\u53d1\u6280\u672f\u535a\u5ba2 | 2017-04-12      |\n| 3          | \u5b66\u4e60 Java     | APPBLOG.CN      | 2015-05-01      |\n| 4          | \u5b66\u4e60 Python   | APPBLOG.CN      | 2016-03-06      |\n| 5          | \u5b66\u4e60 C        | FK              | 2017-04-05      |\n+------------+---------------+-----------------+-----------------+\n5 rows in set (0.01 sec)<\/code><\/pre>\n<p>\u63a5\u4e0b\u6765\u6211\u4eec\u5c31\u4f7f\u7528MySQL\u7684<code>INNER JOIN<\/code>(\u4e5f\u53ef\u4ee5\u7701\u7565<code>INNER<\/code>\u4f7f\u7528<code>JOIN<\/code>\uff0c\u6548\u679c\u4e00\u6837)\u6765\u8fde\u63a5\u4ee5\u4e0a\u4e24\u5f20\u8868\u6765\u8bfb\u53d6<code>appblog_tbl<\/code>\u8868\u4e2d\u6240\u6709<code>appblog_author<\/code>\u5b57\u6bb5\u5728<code>tcount_tbl<\/code>\u8868\u5bf9\u5e94\u7684<code>appblog_count<\/code>\u5b57\u6bb5\u503c\uff1a<\/p>\n<p><strong>INNER JOIN<\/strong><\/p>\n<pre><code class=\"language-sql\">mysql&gt; SELECT a.appblog_id, a.appblog_author, b.appblog_count FROM appblog_tbl a INNER JOIN tcount_tbl b ON a.appblog_author = b.appblog_author;\n+--------------+------------------+-----------------+\n| a.appblog_id | a.appblog_author | b.appblog_count |\n+--------------+------------------+-----------------+\n| 1            | APP\u5f00\u53d1\u6280\u672f\u535a\u5ba2  | 10              |\n| 2            | APP\u5f00\u53d1\u6280\u672f\u535a\u5ba2  | 10              |\n| 3            | APPBLOG.CN       | 20              |\n| 4            | APPBLOG.CN       | 20              |\n+--------------+------------------+-----------------+\n4 rows in set (0.00 sec)<\/code><\/pre>\n<p>\u4ee5\u4e0a SQL \u8bed\u53e5\u7b49\u4ef7\u4e8e\uff1a<\/p>\n<p><strong>WHERE \u5b50\u53e5<\/strong><\/p>\n<pre><code class=\"language-sql\">mysql&gt; SELECT a.appblog_id, a.appblog_author, b.appblog_count FROM appblog_tbl a, tcount_tbl b WHERE a.appblog_author = b.appblog_author;\n+--------------+------------------+-----------------+\n| a.appblog_id | a.appblog_author | b.appblog_count |\n+--------------+------------------+-----------------+\n| 1            | APP\u5f00\u53d1\u6280\u672f\u535a\u5ba2  | 10              |\n| 2            | APP\u5f00\u53d1\u6280\u672f\u535a\u5ba2  | 10              |\n| 3            | APPBLOG.CN       | 20              |\n| 4            | APPBLOG.CN       | 20              |\n+--------------+------------------+-----------------+\n4 rows in set (0.01 sec)<\/code><\/pre>\n<p><img decoding=\"async\" src=\"http:\/\/www.yezhou.me\/AppBlog\/images\/\u6570\u636e\u5e93\/innerjoin.gif\" alt=\"INNER JOIN\" \/><\/p>\n<h2>MySQL LEFT JOIN<\/h2>\n<p><code>MySQL LEFT JOIN<\/code>\u4e0e<code>JOIN<\/code>\u6709\u6240\u4e0d\u540c\u3002<code>MySQL LEFT JOIN<\/code>\u4f1a\u8bfb\u53d6\u5de6\u8fb9\u6570\u636e\u8868\u7684\u5168\u90e8\u6570\u636e\uff0c\u5373\u4fbf\u53f3\u8fb9\u8868\u65e0\u5bf9\u5e94\u6570\u636e\u3002<\/p>\n<p>\u5c1d\u8bd5\u4ee5\u4e0b\u5b9e\u4f8b\uff0c\u4ee5<code>appblog_tbl<\/code>\u4e3a\u5de6\u8868\uff0c<code>tcount_tbl<\/code>\u4e3a\u53f3\u8868\uff0c\u7406\u89e3<code>MySQL LEFT JOIN<\/code>\u7684\u5e94\u7528\uff1a<\/p>\n<p><strong>LEFT JOIN<\/strong><\/p>\n<pre><code class=\"language-sql\">mysql&gt; SELECT a.appblog_id, a.appblog_author, b.appblog_count FROM appblog_tbl a LEFT JOIN tcount_tbl b ON a.appblog_author = b.appblog_author;\n+--------------+------------------+-----------------+\n| a.appblog_id | a.appblog_author | b.appblog_count |\n+--------------+------------------+-----------------+\n| 1            | APP\u5f00\u53d1\u6280\u672f\u535a\u5ba2  | 10              |\n| 2            | APP\u5f00\u53d1\u6280\u672f\u535a\u5ba2  | 10              |\n| 3            | APPBLOG.CN       | 20              |\n| 4            | APPBLOG.CN       | 20              |\n| 5            | FK               | NULL            |\n+--------------+------------------+-----------------+\n5 rows in set (0.01 sec)<\/code><\/pre>\n<p>\u4ee5\u4e0a\u5b9e\u4f8b\u4e2d\u4f7f\u7528\u4e86<code>LEFT JOIN<\/code>\uff0c\u8be5\u8bed\u53e5\u4f1a\u8bfb\u53d6\u5de6\u8fb9\u7684\u6570\u636e\u8868<code>appblog_tbl<\/code>\u7684\u6240\u6709\u9009\u53d6\u7684\u5b57\u6bb5\u6570\u636e\uff0c\u5373\u4fbf\u5728\u53f3\u4fa7\u8868<code>tcount_tbl<\/code>\u4e2d\u6ca1\u6709\u5bf9\u5e94\u7684<code>appblog_author<\/code>\u5b57\u6bb5\u503c\u3002<\/p>\n<p><img decoding=\"async\" src=\"http:\/\/www.yezhou.me\/AppBlog\/images\/\u6570\u636e\u5e93\/leftjoin.gif\" alt=\"LEFT JOIN\" \/><\/p>\n<h2>MySQL RIGHT JOIN<\/h2>\n<p><code>MySQL RIGHT JOIN<\/code>\u4f1a\u8bfb\u53d6\u53f3\u8fb9\u6570\u636e\u8868\u7684\u5168\u90e8\u6570\u636e\uff0c\u5373\u4fbf\u5de6\u8fb9\u8fb9\u8868\u65e0\u5bf9\u5e94\u6570\u636e\u3002<\/p>\n<p>\u5c1d\u8bd5\u4ee5\u4e0b\u5b9e\u4f8b\uff0c\u4ee5<code>appblog_tbl<\/code>\u4e3a\u5de6\u8868\uff0c<code>tcount_tbl<\/code>\u4e3a\u53f3\u8868\uff0c\u7406\u89e3<code>MySQL RIGHT JOIN<\/code>\u7684\u5e94\u7528\uff1a<\/p>\n<p><strong>RIGHT JOIN<\/strong><\/p>\n<pre><code class=\"language-sql\">mysql&gt; SELECT a.appblog_id, a.appblog_author, b.appblog_count FROM appblog_tbl a RIGHT JOIN appblog_tbl b ON a.appblog_author = b.appblog_author;\n+--------------+------------------+-----------------+\n| a.appblog_id | a.appblog_author | b.appblog_count |\n+--------------+------------------+-----------------+\n| 1            | APP\u5f00\u53d1\u6280\u672f\u535a\u5ba2  | 10              |\n| 2            | APP\u5f00\u53d1\u6280\u672f\u535a\u5ba2  | 10              |\n| 3            | APPBLOG.CN       | 20              |\n| 4            | APPBLOG.CN       | 20              |\n| NULL         | NULL             | 22              |\n+--------------+------------------+-----------------+\n5 rows in set (0.01 sec)<\/code><\/pre>\n<p>\u4ee5\u4e0a\u5b9e\u4f8b\u4e2d\u4f7f\u7528\u4e86<code>RIGHT JOIN<\/code>\uff0c\u8be5\u8bed\u53e5\u4f1a\u8bfb\u53d6\u53f3\u8fb9\u7684\u6570\u636e\u8868<code>tcount_tbl<\/code>\u7684\u6240\u6709\u9009\u53d6\u7684\u5b57\u6bb5\u6570\u636e\uff0c\u5373\u4fbf\u5728\u5de6\u4fa7\u8868<code>appblog_tbl<\/code>\u4e2d\u6ca1\u6709\u5bf9\u5e94\u7684<code>appblog_author<\/code>\u5b57\u6bb5\u503c\u3002<\/p>\n<p><img decoding=\"async\" src=\"http:\/\/www.yezhou.me\/AppBlog\/images\/\u6570\u636e\u5e93\/rightjoin.gif\" alt=\"RIGHT JOIN\" \/><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4f7f\u7528 MySQL \u7684 JOIN \u5728\u4e24\u4e2a\u6216\u591a\u4e2a\u8868\u4e2d\u67e5\u8be2\u6570\u636e\u3002\u53ef\u4ee5\u5728 SELECT, UPDATE \u548c DELET [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[13],"tags":[],"class_list":["post-237","post","type-post","status-publish","format-standard","hentry","category-mysql"],"_links":{"self":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/posts\/237","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/comments?post=237"}],"version-history":[{"count":0,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/posts\/237\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/media?parent=237"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/categories?post=237"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/tags?post=237"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}