{"id":200520,"date":"2025-05-06T13:26:34","date_gmt":"2025-05-06T05:26:34","guid":{"rendered":"https:\/\/server.hk\/cnblog\/200520\/"},"modified":"2025-05-06T13:26:34","modified_gmt":"2025-05-06T05:26:34","slug":"java%e6%9f%a5%e8%af%a2sql%e8%bf%94%e5%9b%9eint%e7%b1%bb%e5%9e%8b%e9%81%87%e5%88%b0%e7%a9%ba%e5%80%bc%e5%a6%82%e4%bd%95%e5%a4%84%e7%90%86%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/200520\/","title":{"rendered":"Java\u67e5\u8be2SQL\u8fd4\u56deint\u7c7b\u578b\u9047\u5230\u7a7a\u503c\u5982\u4f55\u5904\u7406\uff1f"},"content":{"rendered":"<p><b><\/b> <\/p>\n<h1>Java\u67e5\u8be2SQL\u8fd4\u56deint\u7c7b\u578b\u9047\u5230\u7a7a\u503c\u5982\u4f55\u5904\u7406\uff1f<\/h1>\n<p>\u4eca\u65e5\u4e0d\u80af\u57cb\u5934\uff0c\u660e\u65e5\u4f55\u4ee5\u62ac\u5934\uff01\u6bcf\u65e5\u4e00\u53e5\u52aa\u529b\u81ea\u5df1\u7684\u8bdd\u54c8\u54c8~\u54c8\u55bd\uff0c\u4eca\u5929\u6211\u5c06\u7ed9\u5927\u5bb6\u5e26\u6765\u4e00\u7bc7\uff0c\u4e3b\u8981\u5185\u5bb9\u662f\u8bb2\u89e3\u7b49\u7b49\uff0c\u611f\u5174\u8da3\u7684\u670b\u53cb\u53ef\u4ee5\u6536\u85cf\u6216\u8005\u6709\u66f4\u597d\u7684\u5efa\u8bae\u5728\u8bc4\u8bba\u63d0\u51fa\uff0c\u6211\u90fd\u4f1a\u8ba4\u771f\u770b\u7684\uff01\u5927\u5bb6\u4e00\u8d77\u8fdb\u6b65\uff0c\u4e00\u8d77\u5b66\u4e60\uff01<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/www.17golang.com\/uploads\/20241107\/1730960879672c5def90476.jpg\" class=\"aligncenter\"><\/p>\n<p><strong>java\u67e5\u8be2sql\u8fd4\u56deint\u7c7b\u578b\uff0c\u9047\u5230\u7a7a\u503c\u629b\u51fa\u5f02\u5e38\u7684\u5904\u7406\u65b9\u6cd5<\/strong><\/p>\n<p>\u5728\u4f7f\u7528java\u7684mybatis\u6846\u67b6\u8fdb\u884c\u6570\u636e\u5e93\u67e5\u8be2\u65f6\uff0c\u6709\u65f6\u5019\u53ef\u80fd\u4f1a\u9047\u5230\u67e5\u8be2\u7ed3\u679c\u4e3anull\u7684\u60c5\u51b5\uff0c\u4f46\u671f\u671b\u7684\u8fd4\u56de\u7c7b\u578b\u4e3aint\uff0c\u8fd9\u5c31\u53ef\u80fd\u5bfc\u81f4\u5f02\u5e38\u3002\u8981\u89e3\u51b3\u6b64\u95ee\u9898\uff0c\u6709\u591a\u79cd\u5904\u7406\u65b9\u6cd5\uff1a<\/p>\n<p><strong>\u65b9\u6cd51\uff1a\u5c06\u8fd4\u56de\u503c\u7c7b\u578b\u6539\u4e3ainteger<\/strong><\/p>\n<p>\u5c06mapper\u63a5\u53e3\u4e2d\u7684\u8fd4\u56de\u503c\u7c7b\u578b\u6539\u4e3ainteger\uff0c\u800c\u975eint\u3002\u8fd9\u6837\uff0cmybatis\u6846\u67b6\u4f1a\u5c06\u7a7a\u503c\u5305\u88c5\u4e3anull\uff0c\u800c\u4e0d\u662f\u629b\u51fa\u5f02\u5e38\u3002\u5177\u4f53\u4fee\u6539\u5982\u4e0b\uff1a<\/p>\n<pre>@select(\"select max(id) from user\")\ninteger maxid();<\/pre>\n<p>\u968f\u540e\uff0c\u5728service\u5c42\u8fdb\u884c\u7a7a\u503c\u5224\u65ad\uff0c\u4f8b\u5982\u8fd4\u56de\u9ed8\u8ba4\u503c0\uff1a<\/p>\n<pre>public int getmaxid() {\n    integer maxid = mapper.maxid();\n    return maxid == null ? 0 : maxid;\n}<\/pre>\n<p><strong>\u65b9\u6cd52\uff1a\u4f7f\u7528ifnull()\u51fd\u6570\u5305\u88f9max<\/strong><\/p>\n<p>\u5728sql\u67e5\u8be2\u4e2d\u4f7f\u7528ifnull()\u51fd\u6570\uff0c\u6307\u5b9a\u7a7a\u503c\u65f6\u8fd4\u56de\u6307\u5b9a\u7684\u503c\u3002\u5177\u4f53\u4fee\u6539\u5982\u4e0b\uff1a<\/p>\n<pre>@Select(\"SELECT ifnull(max(id), 0) FROM user\")\nint maxId();<\/pre>\n<p>\u8fd9\u6837\uff0cmybatis\u6846\u67b6\u76f4\u63a5\u8fd4\u56de\u975enull\u7684\u503c\uff0c\u907f\u514d\u4e86\u5f02\u5e38\u7684\u629b\u51fa\u3002<\/p>\n<p>\u4eca\u5929\u5173\u4e8e\u300aJava\u67e5\u8be2SQL\u8fd4\u56deint\u7c7b\u578b\u9047\u5230\u7a7a\u503c\u5982\u4f55\u5904\u7406\uff1f\u300b\u7684\u5185\u5bb9\u5c31\u4ecb\u7ecd\u5230\u8fd9\u91cc\u4e86\uff0c\u662f\u4e0d\u662f\u5b66\u8d77\u6765\u4e00\u76ee\u4e86\u7136\uff01\u60f3\u8981\u4e86\u89e3\u66f4\u591a\u5173\u4e8e\u7684\u5185\u5bb9\u8bf7\u5173\u6ce8\u4e3b\u673a\u5b9d\u8d1d\u516c\u4f17\u53f7\uff01<\/p>\n<dl>\n<dt>\n <\/dt>\n<\/dl>\n","protected":false},"excerpt":{"rendered":"<p>Java\u67e5\u8be2SQL\u8fd4\u56deint\u7c7b\u578b&#46;&#46;&#46;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-200520","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/200520","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"}],"author":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=200520"}],"version-history":[{"count":0,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/200520\/revisions"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=200520"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=200520"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=200520"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}