{"id":10008263,"date":"2023-09-11T16:14:39","date_gmt":"2023-09-11T08:14:39","guid":{"rendered":"https:\/\/blog.itmax.cn\/?p=10008263"},"modified":"2023-09-11T16:14:39","modified_gmt":"2023-09-11T08:14:39","slug":"%e4%b8%80%e4%b8%aa%e7%83%82%e5%88%86%e9%a1%b5%ef%bc%8c%e8%b8%a9%e4%ba%86%e4%b8%89%e4%b8%aa%e5%9d%91%ef%bc%81","status":"publish","type":"post","link":"https:\/\/itmax.cn\/?p=10008263","title":{"rendered":"\u4e00\u4e2a\u70c2\u5206\u9875\uff0c\u8e29\u4e86\u4e09\u4e2a\u5751\uff01"},"content":{"rendered":"<p>\u4f60\u597d\u5440\uff0c\u6211\u662f\u6b6a\u6b6a\u3002<\/p>\n<p>\u524d\u6bb5\u65f6\u95f4\u8e29\u5230\u4e00\u4e2a\u6bd4\u8f83\u65e0\u8bed\u7684\u751f\u4ea7 BUG\uff0c\u4e25\u683c\u6765\u8bf4\u5176\u5b9e\u4e5f\u4e0d\u80fd\u7b97\u662f BUG\uff0c\u53ea\u80fd\u8bf4\u5f00\u53d1\u540c\u4e8b\u5bf9\u4e8e\u4e1a\u52a1\u540c\u4e8b\u7684\u9700\u6c42\u7406\u89e3\u6ca1\u6709\u5230\u4f4d\u3002<\/p>\n<p>\u8fd9\u4e2a BUG \u5176\u5b9e\u548c\u5206\u9875\u6ca1\u6709\u4efb\u4f55\u5173\u7cfb\uff0c\u4f46\u662f\u5f53\u6211\u53bb\u6392\u67e5\u95ee\u9898\u7684\u65f6\u5019\uff0c\u6211\u770b\u4e86\u4e00\u773c SQL \uff0c\u5927\u6982\u662f\u8fd9\u6837\u7684\uff1a<\/p>\n<blockquote><p>select * from table order by priority limit 1;<\/p><\/blockquote>\n<p>priority\uff0c\u5c31\u662f\u4f18\u5148\u7ea7\u7684\u610f\u601d\u3002<\/p>\n<p>\u6309\u7167\u4f18\u5148\u7ea7 order by \u7136\u540e limit \u53d6\u4f18\u5148\u7ea7\u6700\u9ad8\uff08\u6570\u5b57\u8d8a\u5c0f\uff0c\u4f18\u5148\u7ea7\u8d8a\u9ad8\uff09\u7684\u7b2c\u4e00\u6761 \uff0c\u7ed3\u5408\u4e1a\u52a1\u80cc\u666f\u548c\u6570\u636e\u5e93\u91cc\u9762\u7684\u6570\u636e\uff0c\u6211\u7acb\u9a6c\u5c31\u610f\u8bc6\u5230\u4e86\u95ee\u9898\u6240\u5728\u3002<\/p>\n<p>\u60f3\u8d77\u4e86\u6211\u5f53\u5e74\u5728\u5199\u5206\u9875\u903b\u8f91\u7684\u65f6\u5019\uff0c\u867d\u7136\u573a\u666f\u548c\u8fd9\u4e2a\u5b8c\u5168\u4e0d\u4e00\u6837\uff0c\u4f46\u662f\u8e29\u8fc7\u5230\u5e95\u5c42\u539f\u7406\u4e00\u6a21\u4e00\u6837\u7684\u5751\uff0c\u8fd9\u73a9\u610f\u5370\u8c61\u6df1\u523b\uff0c\u6240\u4ee5\u7acb\u9a6c\u5c31\u8bc6\u522b\u51fa\u6765\u4e86\u3002<\/p>\n<p>\u501f\u7740\u8fd9\u4e2a\u95ee\u9898\uff0c\u4e5f\u76d8\u70b9\u4e00\u4e0b\u6211\u9047\u5230\u8fc7\u7684\u4e09\u4e2a\u5173\u4e8e\u5206\u9875\u67e5\u8be2\u6709\u610f\u601d\u7684\u5751\u3002<\/p>\n<h2>\u804c\u4e1a\u751f\u6daf\u7684\u7b2c\u4e00\u4e2a\u751f\u4ea7 BUG<\/h2>\n<p>\u6b6a\u5e08\u5085\u804c\u4e1a\u751f\u6daf\u7684\u7b2c\u4e00\u4e2a\u751f\u4ea7 BUG \u5c31\u662f\u4e00\u4e2a\u5c0f\u5c0f\u7684\u5206\u9875\u67e5\u8be2\u3002<\/p>\n<p>\u5f53\u65f6\u8fd8\u5728\u505a\u652f\u4ed8\u7cfb\u7edf\uff0c\u63a5\u624b\u7684\u4e00\u4e2a\u9700\u6c42\u4e5f\u5f88\u7b80\u5355\u5c31\u662f\u505a\u4e00\u4e2a\u5b9a\u65f6\u4efb\u52a1\uff0c\u5b9a\u65f6\u628a\u6570\u636e\u5e93\u91cc\u9762\u72b6\u6001\u4e3a\u521d\u59cb\u5316\u7684\u8ba2\u5355\u67e5\u8be2\u51fa\u6765\uff0c\u8c03\u7528\u53e6\u4e00\u4e2a\u670d\u52a1\u63d0\u4f9b\u7684\u63a5\u53e3\u67e5\u8be2\u8ba2\u5355\u7684\u72b6\u6001\u5e76\u66f4\u65b0\u3002<\/p>\n<p>\u7531\u4e8e\u6d41\u7a0b\u4e0a\u6709\u6570\u636e\u5f3a\u6821\u9a8c\uff0c\u4e0d\u7528\u8003\u8651\u6570\u636e\u4e0d\u5b58\u5728\u7684\u60c5\u51b5\u3002\u6240\u4ee5\u8be5\u63a5\u53e3\u53ef\u80fd\u8fd4\u56de\u7684\u72b6\u6001\u53ea\u6709\u4e09\u79cd\uff1a\u6210\u529f\uff0c\u5931\u8d25\uff0c\u5904\u7406\u4e2d\u3002<\/p>\n<p>\u5f88\u7b80\u5355\uff0c\u5f88\u5e38\u89c4\u7684\u4e00\u4e2a\u9700\u6c42\u5bf9\u5427\uff0c\u6211\u5206\u5206\u949f\u5c31\u80fd\u5199\u51fa\u4f2a\u4ee3\u7801\uff1a<\/p>\n<pre><code>\/\/\u83b7\u53d6\u8ba2\u5355\u72b6\u6001\u4e3a\u521d\u59cb\u5316\u7684\u6570\u636e(0:\u521d\u59cb\u5316 1:\u5904\u7406\u4e2d 2:\u6210\u529f 3:\u5931\u8d25)\n\/\/select * from order where order_status=0;\nArrayList initOrderInfoList = queryInitOrderInfoList();\n\/\/\u5faa\u73af\u5904\u7406\u8fd9\u6279\u6570\u636e\nfor(OrderInfo orderInfo : initOrderInfoList){\n    \/\/\u6355\u83b7\u5f02\u5e38\u4ee5\u514d\u4e00\u6761\u6570\u636e\u9519\u8bef\u5bfc\u81f4\u5faa\u73af\u7ed3\u675f\n    try{\n        \/\/\u53d1\u8d77rpc\u8c03\u7528\n        String orderStatus = queryOrderStatus(orderInfo.getOrderId);\n        \/\/\u66f4\u65b0\u8ba2\u5355\u72b6\u6001\n        updateOrderInfo(orderInfo.getOrderId,orderStatus);    \n    } catch (Exception e){\n        \/\/\u6253\u5370\u5f02\u5e38\n    }\n}<\/code><\/pre>\n<p>\u6765\uff0c\u4f60\u8bf4\u4e0a\u9762\u8fd9\u4e2a\u7a0b\u5e8f\u6709\u4ec0\u4e48\u95ee\u9898\uff1f<\/p>\n<p><img decoding=\"async\"   referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/remote\/1460000044204057\" alt=\"\" title=\"\"><\/p>\n<p>\u5176\u5b9e\u5728\u7edd\u5927\u90e8\u5206\u60c5\u51b5\u4e0b\u90fd\u6ca1\u5565\u5927\u95ee\u9898\uff0c\u6570\u636e\u91cf\u4e0d\u591a\u7684\u60c5\u51b5\u4e0b\u7a0b\u5e8f\u8dd1\u8d77\u6765\u6ca1\u6709\u4efb\u4f55\u6bdb\u75c5\u3002<\/p>\n<p>\u4f46\u662f\uff0c\u5982\u679c\u6570\u636e\u91cf\u591a\u8d77\u6765\u4e86\uff0c\u4e00\u6b21\u6027\u628a\u6240\u6709\u521d\u59cb\u5316\u72b6\u6001\u7684\u8ba2\u5355\u90fd\u62ff\u51fa\u6765\uff0c\u662f\u4e0d\u662f\u6709\u70b9\u4e0d\u5408\u7406\u4e86\uff0c\u4e07\u4e00\u628a\u5185\u5b58\u7ed9\u4f60\u6491\u7206\u4e86\u600e\u4e48\u529e\uff1f<\/p>\n<p>\u6240\u4ee5\uff0c\u5728\u6211\u5df2\u77e5\u6570\u636e\u91cf\u4f1a\u5f88\u5927\u7684\u60c5\u51b5\u4e0b\uff0c\u6211\u91c7\u53d6\u4e86\u5206\u6279\u6b21\u83b7\u53d6\u6570\u636e\u7684\u6a21\u5f0f\uff0c\u5047\u8bbe\u4e00\u6b21\u6027\u53d6 100 \u6761\u6570\u636e\u51fa\u6765\u73a9\u3002<\/p>\n<p>\u90a3\u4e48 SQL \u5c31\u662f\u8fd9\u6837\u7684\uff1a<\/p>\n<blockquote><p>select * from order where order_status=0 order by create_time limit 100;<\/p><\/blockquote>\n<p>\u6240\u4ee5\u4e0a\u9762\u7684\u4f2a\u4ee3\u7801\u4f1a\u53d8\u6210\u8fd9\u6837\uff1a<\/p>\n<pre><code>while(true){\n    \/\/\u83b7\u53d6\u8ba2\u5355\u72b6\u6001\u4e3a\u521d\u59cb\u5316\u7684\u6570\u636e(0:\u521d\u59cb\u5316 1:\u5904\u7406\u4e2d 2:\u6210\u529f 3:\u5931\u8d25)\n    \/\/select * from order where order_status=0 order by create_time limit 100;\n    ArrayList initOrderInfoList = queryInitOrderInfoList();\n    \/\/\u5faa\u73af\u5904\u7406\u8fd9\u6279\u6570\u636e\n    for(OrderInfo orderInfo : initOrderInfoList){\n        \/\/\u6355\u83b7\u5f02\u5e38\u4ee5\u514d\u4e00\u6761\u6570\u636e\u9519\u8bef\u5bfc\u81f4\u5faa\u73af\u7ed3\u675f\n        try{\n            \/\/\u53d1\u8d77rpc\u8c03\u7528\n            String orderStatus = queryOrderStatus(orderInfo.getOrderId);\n            \/\/\u66f4\u65b0\u8ba2\u5355\u72b6\u6001\n            updateOrderInfo(orderInfo.getOrderId,orderStatus);    \n        } catch (Exception e){\n            \/\/\u6253\u5370\u5f02\u5e38\n        }\n    }\n}<\/code><\/pre>\n<p>\u6765\uff0c\u4f60\u53c8\u6765\u544a\u8bc9\u6211\u4e0a\u9762\u8fd9\u4e00\u6bb5\u903b\u8f91\u6709\u4ec0\u4e48\u95ee\u9898\uff1f<\/p>\n<p><img decoding=\"async\"   referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/remote\/1460000044204058\" alt=\"\" title=\"\" loading=\"lazy\"><\/p>\n<p>\u4f5c\u4e3a\u7a0b\u5e8f\u5458\uff0c\u6211\u4eec\u770b\u5230 while(true) \u8fd9\u6837\u7684\u5199\u6cd5\u7acb\u9a6c\u5c31\u8981\u8b66\u62a5\u62c9\u6ee1\uff0c\u770b\u770b\u6709\u6ca1\u6709\u6b7b\u5faa\u73af\u7684\u98ce\u9669\u3002<\/p>\n<p>\u90a3\u4f60\u8bf4\u4e0a\u9762\u8fd9\u6bb5\u4ee3\u7801\u5728\u4ec0\u4e48\u65f6\u5019\u9000\u4e0d\u51fa\u6765\uff1f<\/p>\n<p>\u5f53\u6709\u4efb\u4f55\u4e00\u6761\u6570\u636e\u7684\u72b6\u6001\u6ca1\u6709\u4ece\u521d\u59cb\u5316\u53d8\u6210\u6210\u529f\u3001\u5931\u8d25\u6216\u8005\u5904\u7406\u4e2d\u7684\u65f6\u5019\uff0c\u5c31\u4f1a\u5bfc\u81f4\u4e00\u76f4\u5faa\u73af\u3002<\/p>\n<p>\u800c\u867d\u7136\u53d1\u8d77 RPC \u8c03\u7528\u7684\u5730\u65b9\uff0c\u670d\u52a1\u63d0\u4f9b\u65b9\u80fd\u786e\u4fdd\u8fd4\u56de\u7684\u72b6\u6001\u4e00\u5b9a\u662f\u6210\u529f\u3001\u5931\u8d25\u3001\u5904\u7406\u4e2d\u8fd9\u4e09\u8005\u4e4b\u4e2d\u7684\u4e00\u4e2a\uff0c\u4f46\u662f\u8fd9\u4e2a\u6709\u4e00\u4e2a\u524d\u63d0\u662f\u63a5\u53e3\u8c03\u7528\u6b63\u5e38\u7684\u60c5\u51b5\u4e0b\u3002<\/p>\n<p>\u5982\u679c\u63a5\u53e3\u8c03\u7528\u4e00\u65e6\u5f02\u5e38\uff0c\u90a3\u4e48\u6309\u7167\u4e0a\u9762\u7684\u5199\u6cd5\uff0c\u5728\u629b\u51fa\u5f02\u5e38\u540e\uff0c\u72b6\u6001\u5e76\u672a\u53d1\u751f\u53d8\u5316\uff0c\u8fd8\u4f1a\u662f\u505c\u7559\u5728\u201c\u521d\u59cb\u5316\u201d\uff0c\u4ece\u800c\u5bfc\u81f4\u6b7b\u5faa\u73af\u3002<\/p>\n<p>\u5f53\u5e74\uff0c\u6d4b\u8bd5\u540c\u5b66\u5728\u6d4b\u8bd5\u9636\u6bb5\u76f4\u63a5\u5c31\u6d4b\u51fa\u4e86\u8fd9\u4e2a\u95ee\u9898\uff0c\u7136\u540e\u6211\u5bf9\u5176\u8fdb\u884c\u4e86\u4fee\u6539\u3002<\/p>\n<p>\u6211\u6539\u53d8\u4e86\u601d\u8def\uff0c\u628a\u6bcf\u6b21\u5206\u6279\u6b21\u67e5\u8be2 100 \u6761\u6570\u636e\uff0c\u4fee\u6539\u4e3a\u4e86\u5206\u9875\u67e5\u8be2\uff0c\u5f15\u5165\u4e86 PageHelper \u63d2\u4ef6\uff1a<\/p>\n<pre><code>\/\/\u662f\u5426\u662f\u6700\u540e\u4e00\u9875\nwhile(pageInfo.isLastPage){\n    pageNum=pageNum+1;\n    \/\/\u83b7\u53d6\u8ba2\u5355\u72b6\u6001\u4e3a\u521d\u59cb\u5316\u7684\u6570\u636e(0:\u521d\u59cb\u5316 1:\u5904\u7406\u4e2d 2:\u6210\u529f 3:\u5931\u8d25)\n    \/\/select * from order where order_status=0 order by create_time limit pageNum*100,100;\n    PageHelper.startPage(pageNum,100);\n    ArrayList initOrderInfoList = queryInitOrderInfoList();\n    pageInfo = new PageInfo(initOrderInfoList);\n    \/\/\u5faa\u73af\u5904\u7406\u8fd9\u6279\u6570\u636e\n    for(OrderInfo orderInfo : initOrderInfoList){\n        \/\/\u6355\u83b7\u5f02\u5e38\u4ee5\u514d\u4e00\u6761\u6570\u636e\u9519\u8bef\u5bfc\u81f4\u5faa\u73af\u7ed3\u675f\n        try{\n            \/\/\u53d1\u8d77rpc\u8c03\u7528\n            String orderStatus = queryOrderStatus(orderInfo.getOrderId);\n            \/\/\u66f4\u65b0\u8ba2\u5355\u72b6\u6001\n            updateOrderInfo(orderInfo.getOrderId,orderStatus);    \n        } catch (Exception e){\n            \/\/\u6253\u5370\u5f02\u5e38\n        }\n    }\n}<\/code><\/pre>\n<p>\u8df3\u51fa\u5faa\u73af\u7684\u6761\u4ef6\u4e3a\u5224\u65ad\u5f53\u524d\u9875\u662f\u5426\u662f\u6700\u540e\u4e00\u9875\u3002<\/p>\n<p>\u7531\u4e8e\u6bcf\u5faa\u73af\u4e00\u6b21\uff0c\u5f53\u524d\u9875\u5c31\u52a0\u4e00\uff0c\u90a3\u4e48\u7406\u8bba\u4e0a\u8bb2\u4e00\u5b9a\u4f1a\u662f\u7ffb\u5230\u6700\u540e\u4e00\u9875\u7684\uff0c\u6ca1\u6709\u4efb\u4f55\u6bdb\u75c5\uff0c\u5bf9\u4e0d\u5bf9\uff1f<\/p>\n<p>\u6211\u4eec\u53ef\u4ee5\u5206\u6790\u4e00\u4e0b\u4e0a\u9762\u7684\u4ee3\u7801\u903b\u8f91\u3002<\/p>\n<p>\u5047\u8bbe\uff0c\u6211\u4eec\u6709 120 \u6761 order_status=0 \u7684\u6570\u636e\u3002<\/p>\n<p>\u90a3\u4e48\u7b2c\u4e00\u9875\uff0c\u53d6\u51fa\u4e86 100 \u6761\u6570\u636e\uff1a<\/p>\n<blockquote><p>SELECT * from order_info WHERE order_status=0 LIMIT 0,100;<\/p><\/blockquote>\n<p>\u8fd9 100 \u6761\u5904\u7406\u5b8c\u6210\u4e4b\u540e\uff0c\u7b2c\u4e8c\u9875\u8fd8\u6709\u6570\u636e\u5417\uff1f<\/p>\n<p>\u7b2c\u4e8c\u9875\u5bf9\u5e94\u7684 sql \u4e3a\uff1a<\/p>\n<blockquote><p>SELECT * from order_info WHERE order_status=0 LIMIT 100,100;<\/p><\/blockquote>\n<p>\u4f46\u662f\u8fd9\u4e2a\u65f6\u5019\uff0c\u72b6\u6001\u4e3a 0 \u7684\u6570\u636e\uff0c\u53ea\u6709 20 \u6761\u4e86\uff0c\u800c\u5206\u9875\u8981\u4ece\u7b2c 100 \u6761\u5f00\u59cb\uff0c\u662f\u4e0d\u662f\u83b7\u53d6\u4e0d\u5230\u6570\u636e\uff0c\u5bfc\u81f4\u9057\u6f0f\u6570\u636e\u4e86\uff1f<\/p>\n<p>\u786e\u5b9e\u4e00\u5b9a\u4f1a\u7ffb\u5230\u6700\u540e\u4e00\u9875\uff0c\u89e3\u51b3\u4e86\u6b7b\u5faa\u73af\u7684\u95ee\u9898\uff0c\u4f46\u53c8\u6709\u5927\u91cf\u7684\u6570\u636e\u9057\u6f0f\u600e\u4e48\u529e\u5462\uff1f<\/p>\n<p><img decoding=\"async\"   referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/remote\/1460000044204059\" alt=\"\" title=\"\" loading=\"lazy\"><\/p>\n<p>\u5f53\u65f6\u6211\u82e6\u601d\u51a5\u60f3\uff0c\u60f3\u5230\u4e00\u4e2a\u529e\u6cd5\uff1a\u5bfc\u81f4\u6570\u636e\u9057\u6f0f\u7684\u539f\u56e0\u662f\u56e0\u4e3a\u6211\u5728\u7ffb\u9875\u7684\u65f6\u5019\uff0c\u6570\u636e\u72b6\u6001\u5728\u53d8\u5316\uff0c\u5bfc\u81f4\u603b\u4f53\u6570\u636e\u5728\u53d8\u5316\u3002<\/p>\n<p>\u90a3\u4e48\u5982\u679c\u6211\u6bcf\u6b21\u90fd\u4ece\u540e\u5f80\u524d\u53d6\u6570\u636e\uff0c\u6bcf\u6b21\u90fd\u56fa\u5b9a\u53d6\u6700\u540e\u4e00\u9875\uff0c\u80fd\u53d6\u5230\u6570\u636e\u5c31\u4ee3\u8868\u8fd8\u6709\u6570\u636e\u8981\u5904\u7406\uff0c\u5faa\u73af\u7ed3\u675f\u6761\u4ef6\u4fee\u6539\u4e3a\u201c\u5f53\u524d\u9875\u5373\u662f\u7b2c\u4e00\u9875\uff0c\u4e5f\u662f\u6700\u540e\u4e00\u9875\u65f6\u201d\u5c31\u7ed3\u675f\uff0c\u8fd9\u6837\u4e0d\u5c31\u4e0d\u4f1a\u9057\u6f0f\u6570\u636e\u4e86\uff1f<\/p>\n<p>\u6211\u518d\u7ed9\u4f60\u5206\u6790\u4e00\u4e0b\u3002<\/p>\n<p>\u5047\u8bbe\uff0c\u6211\u4eec\u6709 120 \u6761 order_status=0 \u7684\u6570\u636e\uff0c\u4ece\u540e\u5f80\u524d\u53d6\u4e86 100 \u5929\u51fa\u6765\u8fdb\u884c\u51fa\u6765\uff0c\u6709 90 \u6761\u5904\u7406\u6210\u529f\uff0c10 \u6761\u7684\u72b6\u6001\u8fd8\u662f\u505c\u7559\u5728\u201c\u5904\u7406\u4e2d\u201d\u3002<\/p>\n<p>\u7b2c\u4e8c\u6b21\u518d\u53d6\u7684\u65f6\u5019\uff0c\u4f1a\u628a\u5269\u4e0b\u7684 20 \u6761\u548c\u8fd9\u6b21\u201c\u5904\u7406\u4e2d\u201d\u7684 10 \u6761\uff0c\u5171\u8ba1 30 \u6761\u518d\u6b21\u53d6\u51fa\u6765\u8fdb\u884c\u5904\u7406\u3002<\/p>\n<p>\u786e\u4fdd\u6ca1\u6709\u6570\u636e\u9057\u6f0f\u3002<\/p>\n<p>\u540e\u6765\u6d4b\u8bd5\u73af\u8282\u9a8c\u6536\u901a\u8fc7\u4e86\uff0c\u8fd9\u4e2a\u65b9\u6848\u4e0a\u7ebf\u4e4b\u540e\uff0c\u4e5f\u786e\u5b9e\u6ca1\u6709\u9057\u6f0f\u8fc7\u6570\u636e\u4e86\u3002<\/p>\n<p>\u76f4\u5230\u540e\u6765\u53c8\u4e00\u5929\uff0c\u63d0\u4f9b queryOrderStatus \u63a5\u53e3\u7684\u670d\u52a1\u5f02\u5e38\u4e86\uff0c\u6211\u53d1\u8fc7\u53bb\u7684\u8bf7\u6c42\u8d85\u65f6\u4e86\u3002<\/p>\n<p>\u5bfc\u81f4\u6211\u53d6\u51fa\u6765\u7684\u6570\u636e\uff0c\u6bcf\u4e00\u6761\u90fd\u4f1a\u629b\u51fa\u5f02\u5e38\uff0c\u90fd\u4e0d\u4f1a\u66f4\u65b0\u72b6\u6001\u3002\u4ece\u800c\u5bfc\u81f4\u6211\u6bcf\u6b21\u4ece\u540e\u5f80\u524d\u53d6\u6570\u636e\uff0c\u90fd\u53d6\u5230\u7684\u662f\u540c\u4e00\u6279\u6570\u636e\u3002<\/p>\n<p>\u4ece\u7a0b\u5e8f\u4e0a\u7684\u8868\u73b0\u4e0a\u770b\uff0c\u65e5\u5fd7\u75af\u72c2\u7684\u6253\u5370\uff0c\u4f46\u662f\u5176\u5b9e\u4e00\u76f4\u5728\u5904\u7406\u540c\u4e00\u6279\uff0c\u5c31\u662f\u6b7b\u5faa\u73af\u4e86\u3002<\/p>\n<p>\u597d\u5728\u6211\u5f53\u65f6\u8fd8\u5728\u65b0\u624b\u4fdd\u62a4\u671f\uff0c\u9886\u5bfc\u5e2e\u6211\u625b\u4e0b\u6765\u4e86\u3002<\/p>\n<p>\u6700\u540e\u968f\u7740\u4e1a\u52a1\u7684\u53d1\u5c55\uff0c\u8fd9\u5757\u903b\u8f91\u4e5f\u5b8c\u5168\u53d1\u751f\u4e86\u53d8\u5316\uff0c\u903b\u8f91\u7531\u6211\u4eec\u4e3b\u52a8\u53bb\u8c03\u7528 RPC \u63a5\u53e3\u67e5\u8be2\u72b6\u6001\u53d8\u6210\u4e86\uff0c\u4e0b\u6e38\u72b6\u6001\u53d8\u5316\u540e\u8fdb\u884c MQ \u4e3b\u52a8\u901a\u77e5\uff0c\u6240\u4ee5\u6211\u8fd9\u4e00\u5768\u9a9a\u4ee3\u7801\u4e5f\u5c31\u968f\u4e4b\u5149\u8363\u4e0b\u5c97\u3002<\/p>\n<p>\u6211\u73b0\u5728\u60f3\u4e86\u4e00\u4e0b\uff0c\u5176\u5b9e\u8fd9\u4e2a\u573a\u666f\uff0c\u7528\u5206\u9875\u7684\u601d\u60f3\u53bb\u53d6\u6570\u636e\u771f\u7684\u4e0d\u597d\u505a\u3002<\/p>\n<p>\u8fd8\u4e0d\u5982\u7528\u6700\u5f00\u59cb\u7684\u5206\u6279\u6b21\u7684\u601d\u60f3\uff0c\u53ea\u4e0d\u8fc7\u5728\u4f1a\u53d8\u5316\u7684\u201c\u72b6\u6001\u201d\u4e4b\u5916\uff0c\u518d\u52a0\u4e0a\u53e6\u5916\u4e00\u4e2a\u4e0d\u4f1a\u6539\u53d8\u7684\u9650\u5b9a\u6761\u4ef6\uff0c\u6bd4\u5982\u5e38\u89c1\u7684\u521b\u5efa\u65f6\u95f4\uff1a<\/p>\n<blockquote><p>select * from order where order_status=0 and create_time&gt;xxx order by create_time limit 100;<\/p><\/blockquote>\n<p>\u6700\u597d\u4e0d\u8981\u57fa\u4e8e\u72b6\u6001\u53bb\u505a\u5206\u9875\uff0c\u5982\u679c\u4e00\u5b9a\u8981\u57fa\u4e8e\u72b6\u6001\u53bb\u505a\u5206\u9875\uff0c\u90a3\u4e48\u8981\u786e\u4fdd\u72b6\u6001\u5728\u5206\u9875\u903b\u8f91\u91cc\u9762\u4f1a\u626d\u8f6c\u4e0b\u53bb\u3002<\/p>\n<p>\u8fd9\u5c31\u662f\u6211\u804c\u4e1a\u751f\u6daf\u7684\u7b2c\u4e00\u4e2a\u751f\u4ea7 BUG\uff0c\u4e00\u4e2a\u4f4e\u7ea7\u7684\u5206\u9875\u903b\u8f91\u9519\u8bef\u3002<\/p>\n<h2>\u8fd8\u662f\u5206\u9875\uff0c\u53c8\u8e29\u5230\u5751<\/h2>\n<p>\u8fd9\u4e5f\u662f\u5728\u5de5\u4f5c\u7684\u524d\u4e24\u5e74\u9047\u5230\u7684\u4e00\u4e2a\u5173\u4e8e\u5206\u9875\u7684\u5751\u3002<\/p>\n<p>\u6700\u5f00\u59cb\u5728\u5b66\u6821\u7684\u65f6\u5019\uff0c\u5927\u5bb6\u80af\u5b9a\u90fd\u624b\u64b8\u8fc7\u5206\u9875\u903b\u8f91\uff0c\u81ea\u5df1\u53bb\u7b97\u603b\u9875\u6570\uff0c\u5f53\u524d\u9875\uff0c\u9875\u9762\u5927\u5c0f\u5565\u7684\u3002<\/p>\n<p>\u5f53\u65f6\u529f\u529b\u5c1a\u6d45\uff0c\u89c9\u5f97\u8fd9\u90e8\u5206\u903b\u8f91\u5199\u8d77\u6765\u662f\u771f\u590d\u6742\uff0c\u4f46\u662f\u6263\u6263\u8111\u888b\u4e5f\u8fd8\u662f\u53ef\u4ee5\u5199\u51fa\u6765\u3002<\/p>\n<p>\u540e\u6765\u53c2\u52a0\u5de5\u4f5c\u4e86\u4e4b\u540e\uff0c\u5728\u9879\u76ee\u91cc\u9762\u770b\u5230\u4e86 PageHelper \u8fd9\u4e2a\u73a9\u610f\uff0c\u4e86\u89e3\u4e4b\u540e\u53d1\u4e86\u201c\u65af\u56fd\u4e00\u201d\u7684\u60ca\u53f9\uff1a\u6709\u4e86\u8fd9\u73a9\u610f\uff0c\u8c01\u8fd8\u624b\u5199\u5206\u9875\u554a\u3002<\/p>\n<p><img decoding=\"async\"   referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/remote\/1460000044204060\" alt=\"\" title=\"\" loading=\"lazy\"><\/p>\n<p>\u4f46\u662f\u6211\u5728\u4f7f\u7528 PageHelper \u7684\u65f6\u5019\uff0c\u4e5f\u8e29\u5230\u8fc7\u4e00\u4e2a\u7ecf\u5178\u7684\u201c\u5751\u201d\u3002<\/p>\n<p>\u6700\u5f00\u59cb\u7684\u65f6\u5019\uff0c\u4ee3\u7801\u662f\u8fd9\u6837\u7684\uff1a<\/p>\n<pre><code>PageHelper.startPage(pageNum,100);\nList&lt;OrderInfo&gt; list = orderInfoMapper.select(param1);<\/code><\/pre>\n<p>\u540e\u6765\u4e3a\u4e86\u907f\u514d\u4e0d\u5e26 where \u6761\u4ef6\u7684\u5168\u8868\u67e5\u8be2\uff0c\u6211\u628a\u4ee3\u7801\u4fee\u6539\u6210\u4e86\u8fd9\u6837\uff1a<\/p>\n<pre><code>PageHelper.startPage(pageNum,100);\nif(param != null){\n    List&lt;OrderInfo&gt; list = orderInfoMapper.select(param);\n}<\/code><\/pre>\n<p>\u7136\u540e\uff0c\u968f\u7740\u7a0b\u5e8f\u7684\u8fed\u4ee3\uff0c\u5c31\u51fa BUG \u4e86\u3002\u56e0\u4e3a\u6709\u7684\u4e1a\u52a1\u573a\u666f\u4e0b\uff0cparam \u53c2\u6570\u4e00\u8def\u4f20\u9012\u8fdb\u6765\u4e4b\u540e\u5c31\u53d8\u6210\u4e86 null\u3002<\/p>\n<p>\u4f46\u662f\u8fd9\u4e2a\u65f6\u5019 PageHelper \u5df2\u7ecf\u5728\u5f53\u524d\u7ebf\u7a0b\u7684 ThreadLocal \u91cc\u9762\u8bbe\u7f6e\u4e86\u5206\u9875\u53c2\u6570\u4e86\uff0c\u4f46\u662f\u6ca1\u6709\u88ab\u6d88\u8d39\uff0c\u8fd9\u4e2a\u53c2\u6570\u5c31\u4f1a\u4e00\u76f4\u4fdd\u7559\u5728\u8fd9\u4e2a\u7ebf\u7a0b\u4e0a\uff0c\u4e5f\u5c31\u662f\u653e\u5728\u7ebf\u7a0b\u7684 ThreadLocal \u91cc\u9762\u3002<\/p>\n<p>\u5f53\u8fd9\u4e2a\u7ebf\u7a0b\u7ee7\u7eed\u5f80\u540e\u8dd1\uff0c\u6216\u8005\u88ab\u590d\u7528\u7684\u65f6\u5019\uff0c\u9047\u5230\u4e00\u6761 SQL \u8bed\u53e5\u65f6\uff0c\u5c31\u53ef\u80fd\u5bfc\u81f4\u4e0d\u8be5\u5206\u9875\u7684\u65b9\u6cd5\u53bb\u6d88\u8d39\u8fd9\u4e2a\u5206\u9875\u53c2\u6570\uff0c\u4ea7\u751f\u4e86\u83ab\u540d\u5176\u5999\u7684\u5206\u9875\u3002<\/p>\n<p>\u6240\u4ee5\uff0c\u4e0a\u9762\u8fd9\u4e2a\u4ee3\u7801\uff0c\u5e94\u8be5\u5199\u6210\u4e0b\u9762\u8fd9\u4e2a\u6837\u5b50\uff1a<\/p>\n<pre><code>if(param != null){\n    PageHelper.startPage(pageNum,100);\n    List&lt;OrderInfo&gt; list = orderInfoMapper.select(param);\n}<\/code><\/pre>\n<p>\u4e5f\u662f\u8fd9\u6b21\u8e29\u5751\u4e4b\u540e\uff0c\u6211\u7ffb\u9605\u4e86 PageHelper \u7684\u6e90\u7801\uff0c\u4e86\u89e3\u4e86\u5e95\u5c42\u539f\u7406\uff0c\u5e76\u603b\u7ed3\u4e86\u4e00\u53e5\u8bdd\uff1a\u9700\u8981\u4fdd\u8bc1\u5728 PageHelper \u65b9\u6cd5\u8c03\u7528\u540e\u7d27\u8ddf MyBatis \u67e5\u8be2\u65b9\u6cd5\uff0c\u5426\u5219\u4f1a\u6c61\u67d3\u7ebf\u7a0b\u3002<\/p>\n<p>\u5728\u6b63\u786e\u4f7f\u7528 PageHelper \u7684\u60c5\u51b5\u4e0b\uff0c\u5176\u63d2\u4ef6\u5185\u90e8\uff0c\u4f1a\u5728 finally \u4ee3\u7801\u6bb5\u4e2d\u81ea\u52a8\u6e05\u9664\u4e86\u5728 ThreadLocal \u4e2d\u5b58\u50a8\u7684\u5bf9\u8c61\u3002<\/p>\n<p>\u8fd9\u6837\u5c31\u4e0d\u4f1a\u7559\u5751\u3002<\/p>\n<p>\u8fd9\u6b21\u7ffb\u9875\u6e90\u7801\u7684\u8fc7\u7a0b\u5f71\u54cd\u4e5f\u662f\u6bd4\u8f83\u6df1\u523b\u7684\uff0c\u867d\u7136\u90a3\u4e2a\u65f6\u5019\u7ecf\u9a8c\u4e0d\u591a\uff0c\u4f46\u662f\u5f97\u76ca\u4e8e MyBatis \u7684\u6e90\u7801\u548c PageHelper \u7684\u6e90\u7801\u5199\u7684\u90fd\u975e\u5e38\u7684\u7b26\u5408\u6b63\u5e38\u4eba\u7684\u601d\u7ef4\uff0c\u9605\u8bfb\u8d77\u6765\u95e8\u69db\u4e0d\u9ad8\uff0c\u518d\u52a0\u4e0a\u6211\u6709\u5177\u4f53\u7684\u7591\u95ee\uff0c\u6240\u4ee5\u90a3\u662f\u4e00\u6b21\u53e4\u65e9\u65f6\u671f\uff0c\u5c1a\u5728\u65b0\u624b\u6751\u65f6\uff0c\u4e3a\u6570\u4e0d\u591a\u7684\uff0c\u9605\u8bfb\u6e90\u7801\u4e4b\u540e\uff0c\u611f\u89c9\u6536\u83b7\u6ee1\u6ee1\u7684\u7ecf\u5386\u3002<\/p>\n<h2>\u5206\u9875\u4e22\u6570\u636e<\/h2>\n<p>\u5173\u4e8e\u8fd9\u4e2a BUG \u53ef\u4ee5\u8bf4\u662f\u5370\u8c61\u6df1\u523b\u4e86\u3002<\/p>\n<p>\u5f53\u5e74\u9047\u5230\u8fd9\u4e2a\u5751\u7684\u65f6\u5019\u6392\u67e5\u4e86\u5f88\u957f\u65f6\u95f4\u6ca1\u5565\u5934\u7eea\uff0c\u6700\u540e\u8fd8\u662f\u7ec4\u91cc\u7684\u5927\u4f6c\u6307\u4e86\u6761\u8def\u3002<\/p>\n<p>\u4e1a\u52a1\u9700\u6c42\u5f88\u7b80\u5355\uff0c\u5c31\u662f\u5728\u7ba1\u7406\u9875\u9762\u4e0a\u53ef\u4ee5\u67e5\u8be2\u8ba2\u5355\u5217\u8868\uff0c\u67e5\u8be2\u7ed3\u679c\u6309\u7167\u8ba2\u5355\u7684\u521b\u5efa\u65f6\u95f4\u5012\u5e8f\u6392\u5e8f\u3002<\/p>\n<p>\u5bf9\u5e94\u7684\u5206\u9875 SQL \u5f88\u7b80\u5355\uff0c\u5f88\u5e38\u89c4\uff0c\u6ca1\u6709\u4efb\u4f55\u95ee\u9898\uff1a<\/p>\n<blockquote><p>select * from table order by create_time desc limit 0,10;<\/p><\/blockquote>\n<p>\u4f46\u662f\u5f53\u5e74\u5728\u9875\u9762\u4e0a\u7684\u8868\u73b0\u5927\u6982\u662f\u8fd9\u6837\u7684\uff1a<\/p>\n<p><img decoding=\"async\"   referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/remote\/1460000044204061\" alt=\"\" title=\"\" loading=\"lazy\"><\/p>\n<p>\u8ba2\u5355\u7f16\u53f7\u4e3a 5 \u7684\u8fd9\u6761\u6570\u636e\uff0c\u4f1a\u540c\u65f6\u51fa\u73b0\u5728\u4e86\u7b2c\u4e00\u9875\u548c\u7b2c\u4e8c\u9875\u3002<\/p>\n<p>\u751a\u81f3\u6709\u7684\u6570\u636e\u5728\u7b2c\u4e8c\u9875\u51fa\u73b0\u4e86\u4e4b\u540e\uff0c\u5728\u7b2c\u4e94\u9875\u53c8\u51fa\u73b0\u4e00\u6b21\u3002<\/p>\n<p>\u540e\u6765\u5b9a\u4f4d\u5230\u4ea7\u751f\u8fd9\u4e2a\u95ee\u9898\u7684\u539f\u56e0\u662f\u56e0\u4e3a\u6709\u4e00\u6279\u6570\u91cf\u4e0d\u5c0f\u7684\u8ba2\u5355\u6570\u636e\u662f\u901a\u8fc7\u7ebf\u4e0b\u6267\u884c SQL \u7684\u65b9\u5f0f\u5bfc\u5165\u7684\u3002<\/p>\n<p>\u800c\u5bfc\u5165\u7684\u8fd9\u4e00\u6279\u6570\u636e\uff0c\u5199 SQL \u7684\u540c\u5b66\u4e3a\u4e86\u65b9\u4fbf\uff0c\u5c31\u628a create_time \u90fd\u8bbe\u7f6e\u4e3a\u4e86\u540c\u4e00\u4e2a\u503c\uff0c\u6bd4\u5982\u90fd\u8bbe\u7f6e\u4e3a\u4e86 2023-09-10 12:34:56 \u8fd9\u4e2a\u65f6\u95f4\u3002<\/p>\n<p>\u7531\u4e8e create_time \u53c8\u662f\u6211\u4f5c\u4e3a order by \u7684\u5b57\u6bb5\uff0c\u5f53\u8fd9\u4e2a\u5b57\u6bb5\u7684\u503c\u5927\u91cf\u90fd\u662f\u540c\u4e00\u4e2a\u503c\u7684\u65f6\u5019\uff0c\u5c31\u4f1a\u5bfc\u81f4\u4e0a\u9762\u7684\u4e00\u6761\u6570\u636e\u5728\u4e0d\u540c\u7684\u9875\u9762\u4e0a\u591a\u6b21\u51fa\u73b0\u7684\u60c5\u51b5\u3002<\/p>\n<p>\u9488\u5bf9\u8fd9\u4e2a\u73b0\u8c61\uff0c\u5f53\u65f6\u7ec4\u91cc\u7684\u5927\u4f6c\u5206\u6790\u660e\u767d\u4e4b\u540e\uff0c\u6254\u7ed9\u6211\u4e00\u4e2a\u94fe\u63a5\uff1a<\/p>\n<blockquote><p><a target=\"_blank\" href=\"https:\/\/link.segmentfault.com\/?enc=hVTVhHDePmm2bG6pNCYDyg%3D%3D.wcy4KMIYjQfP8pg6dxInxyRMaNSKEekUJRmV0QyBItly8oW%2F5U7a%2FaHCgzdk8fDKQF6aJCm1VqN7sHAlYzhbFg%3D%3D\" rel=\"noopener noreferrer\">https:\/\/dev.mysql.com\/doc\/refman\/5.7\/en\/limit-optimization.html<\/a><\/p><\/blockquote>\n<p>\u8fd9\u662f MySQL \u5b98\u65b9\u6587\u6863\uff0c\u8fd9\u4e00\u7ae0\u8282\u53eb\u505a\u201c\u5bf9 Limit \u67e5\u8be2\u7684\u4f18\u5316\u201d\u3002<\/p>\n<p>\u5f00\u7bc7\u7684\u65f6\u5019\u4eba\u5bb6\u5c31\u662f\u8fd9\u6837\u8bf4\u7684\uff1a<\/p>\n<p><img decoding=\"async\"   referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/remote\/1460000044204062\" alt=\"\" title=\"\" loading=\"lazy\"><\/p>\n<p>\u5982\u679c\u5c06 LIMIT row_count \u548c ORDER BY \u7ec4\u5408\u5728\u4e00\u8d77\uff0c\u90a3\u4e48 MySQL \u5728\u627e\u5230\u6392\u5e8f\u7ed3\u679c\u7684\u7b2c\u4e00\u884c count \u884c\u65f6\u5c31\u505c\u6b62\u6392\u5e8f\uff0c\u800c\u4e0d\u662f\u5bf9\u6574\u4e2a\u7ed3\u679c\u8fdb\u884c\u6392\u5e8f\u3002<\/p>\n<p>\u7136\u540e\u7ed9\u4e86\u8fd9\u4e00\u6bb5\u8865\u5145\u8bf4\u660e\uff1a<\/p>\n<p><img decoding=\"async\"   referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/remote\/1460000044204063\" alt=\"\" title=\"\" loading=\"lazy\"><\/p>\n<p>\u5982\u679c\u591a\u6761\u8bb0\u5f55\u7684 ORDER BY \u5217\u4e2d\u6709\u76f8\u540c\u7684\u503c\uff0c\u670d\u52a1\u5668\u53ef\u4ee5\u81ea\u7531\u5730\u6309\u4efb\u4f55\u987a\u5e8f\u8fd4\u56de\u8fd9\u4e9b\u8bb0\u5f55\uff0c\u5e76\u53ef\u80fd\u6839\u636e\u6574\u4f53\u6267\u884c\u8ba1\u5212\u7684\u4e0d\u540c\u800c\u91c7\u53d6\u4e0d\u540c\u7684\u65b9\u5f0f\u3002<\/p>\n<p>\u6362\u53e5\u8bdd\u8bf4\uff0c\u76f8\u5bf9\u4e8e\u672a\u6392\u5e8f\u5217\uff0c\u8fd9\u4e9b\u8bb0\u5f55\u7684\u6392\u5e8f\u987a\u5e8f\u662f nondeterministic \u7684\uff1a<\/p>\n<p><img decoding=\"async\"   referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/remote\/1460000044204064\" alt=\"\" title=\"\" loading=\"lazy\"><\/p>\n<p>\u7136\u540e\u5b98\u65b9\u7ed9\u4e86\u4e00\u4e2a\u793a\u4f8b\u3002<\/p>\n<p>\u9996\u5148\uff0c\u4e0d\u5e26 limit \u7684\u65f6\u5019\u67e5\u8be2\u7ed3\u679c\u662f\u8fd9\u6837\u7684\uff1a<\/p>\n<p><img decoding=\"async\"   referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/remote\/1460000044204065\" alt=\"\" title=\"\" loading=\"lazy\"><\/p>\n<p>\u57fa\u4e8e\u8fd9\u4e2a\u7ed3\u679c\uff0c\u5982\u679c\u6211\u8981\u53d6\u524d\u4e94\u6761\u6570\u636e\uff0c\u5bf9\u5e94\u7684 id \u5e94\u8be5\u662f 1,5,3,4,6\u3002<\/p>\n<p>\u4f46\u662f\u5f53\u6211\u4eec\u5e26\u7740 limit \u7684\u65f6\u5019\u67e5\u8be2\u7ed3\u679c\u53ef\u80fd\u662f\u8fd9\u6837\u7684\uff1a<\/p>\n<p><img decoding=\"async\"   referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/remote\/1460000044204066\" alt=\"\" title=\"\" loading=\"lazy\"><\/p>\n<p>\u5bf9\u5e94\u7684 id \u5b9e\u9645\u662f 1,5,4,3,6\u3002<\/p>\n<p>\u8fd9\u5c31\u662f\u524d\u9762\u8bf4\u7684\uff1a\u5982\u679c\u591a\u6761\u8bb0\u5f55\u7684 ORDER BY \u5217\u4e2d\u6709\u76f8\u540c\u7684\u503c\uff0c\u670d\u52a1\u5668\u53ef\u4ee5\u81ea\u7531\u5730\u6309\u4efb\u4f55\u987a\u5e8f\u8fd4\u56de\u8fd9\u4e9b\u8bb0\u5f55\uff0c\u5e76\u53ef\u80fd\u6839\u636e\u6574\u4f53\u6267\u884c\u8ba1\u5212\u7684\u4e0d\u540c\u800c\u91c7\u53d6\u4e0d\u540c\u7684\u65b9\u5f0f\u3002<\/p>\n<p>\u4ece\u7a0b\u5e8f\u4e0a\u7684\u8868\u73b0\u4e0a\u6765\u770b\uff0c\u7ed3\u679c\u5c31\u662f nondeterministic\u3002<\/p>\n<p>\u6240\u4ee5\u770b\u5230\u8fd9\u91cc\uff0c\u6211\u4eec\u5927\u6982\u53ef\u4ee5\u77e5\u9053\u6211\u524d\u9762\u9047\u5230\u7684\u5206\u9875\u95ee\u9898\u7684\u539f\u56e0\u662f\u56e0\u4e3a\u90a3\u4e00\u6279\u624b\u52a8\u63d2\u5165\u7684\u6570\u636e\u5bf9\u5e94\u7684 create_time \u5b57\u6bb5\u90fd\u662f\u4e00\u6837\u7684\uff0c\u800c MySQL \u8fd9\u8fb9\u53c8\u5bf9 Limit \u53c2\u6570\u505a\u4e86\u4f18\u5316\uff0c\u8fd0\u884c\u7ed3\u679c\u51fa\u73b0\u4e86\u4e0d\u786e\u5b9a\u6027\uff0c\u4ece\u800c\u9875\u9762\u4e0a\u51fa\u73b0\u4e86\u91cd\u590d\u7684\u6570\u636e\u3002<\/p>\n<p>\u800c\u56de\u5230\u6587\u7ae0\u6700\u5f00\u59cb\u7684\u8fd9\u4e2a SQL\uff0c\u4e5f\u5c31\u662f\u6211\u4e00\u773c\u770b\u51fa\u95ee\u9898\u7684\u8fd9\u4e2a SQL\uff1a<\/p>\n<blockquote><p>select * from table order by priority limit 1;<\/p><\/blockquote>\n<p>\u56e0\u4e3a\u5728\u6211\u4eec\u7684\u754c\u9762\u4e0a\uff0c\u53ea\u662f\u7ea6\u5b9a\u4e86\u6570\u5b57\u8d8a\u5c0f\u4f18\u5148\u7ea7\u8d8a\u9ad8\uff0c\u6570\u5b57\u5fc5\u987b\u5927\u4e8e 0\u3002<\/p>\n<p>\u6240\u4ee5\u5f53\u5927\u5bb6\u5728\u8f93\u5165\u4f18\u5148\u7ea7\u7684\u65f6\u5019\uff0c\u5927\u90e8\u5206\u60c5\u51b5\u4e0b\u90fd\u9ed8\u8ba4\u81ea\u5df1\u7f16\u8f91\u7684\u6570\u636e\u5bf9\u5e94\u7684\u4f18\u5148\u7ea7\u6700\u9ad8\uff0c\u4e5f\u5c31\u662f\u8bbe\u7f6e\u4e3a 1\uff0c\u4ece\u800c\u5bfc\u81f4\u6570\u636e\u5e93\u91cc\u9762\u6709\u5927\u91cf\u7684\u4f18\u5148\u7ea7\u4e3a 1 \u7684\u6570\u636e\u3002<\/p>\n<p>\u800c\u7a0b\u5e8f\u6bcf\u6b21\u5904\u7406\uff0c\u53c8\u53ea\u4f1a\u6309\u7167\u4f18\u5148\u7ea7\u6392\u5e8f\u53ea\u4f1a\uff0c\u53d6\u4e00\u6761\u6570\u636e\u51fa\u6765\u8fdb\u884c\u5904\u7406\u3002<\/p>\n<p>\u7ecf\u8fc7\u524d\u9762\u7684\u5206\u6790\u6211\u4eec\u53ef\u4ee5\u77e5\u9053\uff0c\u8fd9\u6837\u53d6\u51fa\u6765\u7684\u6570\u636e\uff0c\u4e0d\u4e00\u5b9a\u6bcf\u6b21\u90fd\u4e00\u6837\u3002<\/p>\n<p>\u6240\u4ee5\u7531\u4e8e\u6709\u8fd9\u6bb5\u4ee3\u7801\u7684\u5b58\u5728\uff0c\u5bfc\u81f4\u4e1a\u52a1\u4e0a\u7684\u8868\u73b0\u5c31\u5f88\u5947\u602a\uff0c\u660e\u660e\u662f\u4e00\u6a21\u4e00\u6837\u7684\u8bf7\u6c42\u53c2\u6570\uff0c\u4f46\u662f\u6700\u7ec8\u8fd4\u56de\u7684\u7ed3\u679c\u53ef\u80fd\u4e0d\u76f8\u540c\u3002<\/p>\n<p>\u597d\uff0c\u73b0\u5728\uff0c\u6211\u95ee\u4f60\uff0c\u4f60\u8bf4\u5728\u524d\u9762\uff0c\u6211\u7ed9\u51fa\u7684\u8fd9\u6837\u7684\u5206\u9875\u67e5\u8be2\u7684 SQL \u8bed\u53e5\u6709\u6ca1\u6709\u6bdb\u75c5\uff1f<\/p>\n<blockquote><p>select * from table order by create_time desc limit 0,10;<\/p><\/blockquote>\n<p>\u6ca1\u6709\u4efb\u4f55\u6bdb\u75c5\u561b\uff0c\u6267\u884c\u7ed3\u679c\u4e5f\u6ca1\u6709\u4efb\u4f55\u6bdb\u75c5\uff1f<\/p>\n<p>\u6709\u6ca1\u6709\u7ed9\u4f60\u6309\u7167 create_time \u6392\u5e8f\uff1f<\/p>\n<p>\u6478\u7740\u826f\u5fc3\u8bf4\uff0c\u662f\u6709\u7684\u3002<\/p>\n<p>\u6709\u6ca1\u6709\u7ed9\u4f60\u53d6\u51fa\u6392\u5e8f\u540e\u7684 10 \u6761\u6570\u636e\uff1f<\/p>\n<p>\u4e5f\u662f\u6709\u7684\u3002<\/p>\n<p>\u6240\u4ee5\uff0c\u9488\u5bf9\u8fd9\u79cd\u73b0\u8c61\uff0c\u5b98\u65b9\u7684\u6001\u5ea6\u662f\uff1a\u6211\u6ca1\u9519\uff01\u5728\u6211\u7684\u6982\u5ff5\u91cc\u9762\uff0c\u6ca1\u6709\u201c\u5206\u9875\u201d\u8fd9\u6837\u7684\u73a9\u610f\uff0c\u4f60\u901a\u8fc7\u7ec4\u5408\u6211\u63d0\u4f9b\u7684\u529f\u80fd\uff0c\u641e\u51fa\u4e86\u201c\u5206\u9875\u201d\u8fd9\u79cd\u4e1a\u52a1\u573a\u666f\uff0c\u73b0\u5728\u4e1a\u52a1\u573a\u666f\u51fa\u95ee\u9898\u4e86\uff0c\u4f60\u53cd\u8fc7\u6765\u8bf4\u6211\u5e95\u5c42\u6709\u95ee\u9898\uff1f<\/p>\n<p>\u8fd9\u4e0d\u662f\u6b3a\u8d1f\u8001\u5b9e\u4eba\u5417\uff1f\u6211\u6ca1\u9519\uff01<\/p>\n<p><img decoding=\"async\"   referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/remote\/1460000044204067\" alt=\"\" title=\"\" loading=\"lazy\"><\/p>\n<p>\u6240\u4ee5\uff0c\u5b98\u65b9\u628a\u8fd9\u4e24\u79cd\u6848\u4f8b\u90fd\u62ff\u51fa\u6765\uff0c\u5e76\u4e14\u5f3a\u8c03\uff1a<\/p>\n<blockquote><p>\u5728\u6bcf\u79cd\u60c5\u51b5\u4e0b\uff0c\u67e5\u8be2\u7ed3\u679c\u90fd\u662f\u6309 ORDER BY \u7684\u5217\u8fdb\u884c\u6392\u5e8f\u7684\uff0c\u8fd9\u6837\u7684\u7ed3\u679c\u662f\u7b26\u5408 SQL \u6807\u51c6\u7684\u3002<\/p><\/blockquote>\n<p><img decoding=\"async\"   referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/remote\/1460000044204068\" alt=\"\" title=\"\" loading=\"lazy\"><\/p>\n<p>\u867d\u7136\u6211\u6ca1\u9519\uff0c\u4f46\u662f\u6211\u8fd8\u662f\u53ef\u4ee5\u7ed9\u4f60\u6307\u4e2a\u8def\u3002<\/p>\n<p>\u5982\u679c\u4f60\u975e\u5e38\u5728\u610f\u6267\u884c\u7ed3\u679c\u7684\u987a\u5e8f\uff0c\u90a3\u4e48\u5728 ORDER BY \u5b50\u53e5\u4e2d\u5305\u542b\u4e00\u4e2a\u989d\u5916\u7684\u5217\uff0c\u4ee5\u786e\u4fdd\u987a\u5e8f\u5177\u6709\u786e\u5b9a\u6027\u3002<\/p>\n<p>\u4f8b\u5982\uff0c\u5982\u679c id \u503c\u662f\u552f\u4e00\u7684\uff0c\u4f60\u53ef\u4ee5\u901a\u8fc7\u8fd9\u6837\u7684\u6392\u5e8f\u4f7f\u7ed9\u5b9a\u7c7b\u522b\u503c\u7684\u884c\u6309 id \u987a\u5e8f\u51fa\u73b0\u3002<\/p>\n<p>\u4f60\u8fd9\u6837\u53bb\u5199\uff0c\u6392\u5e8f\u7684\u65f6\u5019\u52a0\u4e2a id \u5b57\u6bb5\uff0c\u5c31\u7a33\u4e86\uff1a<\/p>\n<p><img decoding=\"async\"   referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/remote\/1460000044204069\" alt=\"\" title=\"\" loading=\"lazy\"><\/p>\n<p>\u597d\u4e86\uff0c\u5982\u679c\u89c9\u5f97\u672c\u6587\u5bf9\u4f60\u6709\u5e2e\u52a9\u7684\u8bdd\uff0c\u6c42\u4e2a\u514d\u8d39\u7684\u70b9\u8d5e\uff0c\u4e0d\u8fc7\u5206\u5427\uff1f<\/p>\n<p><a href=\"https:\/\/segmentfault.com\/a\/1190000044204055\">https:\/\/segmentfault.com\/a\/1190000044204055<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4f60\u597d\u5440\uff0c\u6211\u662f\u6b6a\u6b6a\u3002 \u524d\u6bb5\u65f6\u95f4\u8e29\u5230\u4e00\u4e2a\u6bd4\u8f83\u65e0\u8bed\u7684\u751f\u4ea7 BUG\uff0c\u4e25\u683c\u6765\u8bf4\u5176\u5b9e\u4e5f\u4e0d\u80fd\u7b97\u662f BUG\uff0c\u53ea\u80fd\u8bf4\u5f00\u53d1\u540c\u4e8b\u5bf9\u4e8e [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[4],"tags":[],"class_list":["post-10008263","post","type-post","status-publish","format-standard","hentry","category-share"],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts\/10008263","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=10008263"}],"version-history":[{"count":0,"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts\/10008263\/revisions"}],"wp:attachment":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=10008263"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=10008263"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=10008263"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}