{"id":854,"date":"2021-09-13T14:35:00","date_gmt":"2021-09-13T06:35:00","guid":{"rendered":"http:\/\/www.langmanezhuang.com\/index.php\/2021\/09\/13\/%e5%9f%ba%e4%ba%8e%e9%98%bf%e9%87%8c%e5%b7%b4%e5%b7%b4-mysql%e8%a7%84%e7%ba%a6-%e8%a7%84%e8%8c%83-%e6%80%bb%e7%bb%93\/"},"modified":"2021-09-13T14:35:00","modified_gmt":"2021-09-13T06:35:00","slug":"%e5%9f%ba%e4%ba%8e%e9%98%bf%e9%87%8c%e5%b7%b4%e5%b7%b4-mysql%e8%a7%84%e7%ba%a6-%e8%a7%84%e8%8c%83-%e6%80%bb%e7%bb%93","status":"publish","type":"post","link":"http:\/\/blog.langmanezhuang.com\/index.php\/2021\/09\/13\/%e5%9f%ba%e4%ba%8e%e9%98%bf%e9%87%8c%e5%b7%b4%e5%b7%b4-mysql%e8%a7%84%e7%ba%a6-%e8%a7%84%e8%8c%83-%e6%80%bb%e7%bb%93\/","title":{"rendered":"\u57fa\u4e8e\u963f\u91cc\u5df4\u5df4-Mysql\u89c4\u7ea6\/\u89c4\u8303 \u603b\u7ed3"},"content":{"rendered":"<ul>\n<li>\u4e00\uff1a\u5efa\u8868\u89c4\u7ea6<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<div class=\"cnblogs_Highlighter\">\n<pre class=\"brush:bash;gutter:true;\">1. \u3010\u5f3a\u5236\u3011\u8868\u8fbe\u662f\u4e0e\u5426\u6982\u5ff5\u7684\u5b57\u6bb5\uff0c\u5fc5\u987b\u4f7f\u7528is_xxx\u7684\u65b9\u5f0f\u547d\u540d\uff0c\u6570\u636e\u7c7b\u578b\u662funsignedtinyint\n\n \uff08 1\u8868\u793a\u662f\uff0c0\u8868\u793a\u5426\uff09\uff0c\u6b64\u89c4\u5219\u540c\u6837\u9002\u7528\u4e8eodps\u5efa\u8868\u3002\n\n \u8bf4\u660e\uff1a\u4efb\u4f55\u5b57\u6bb5\u5982\u679c\u4e3a\u975e\u8d1f\u6570\uff0c\u5fc5\u987b\u662funsigned\u3002\n\n2. \u3010\u5f3a\u5236\u3011\u8868\u540d\u3001\u5b57\u6bb5\u540d\u5fc5\u987b\u4f7f\u7528\u5c0f\u5199\u5b57\u6bcd\u6216\u6570\u5b57\uff1b\u7981\u6b62\u51fa\u73b0\u6570\u5b57\u5f00\u5934\uff0c\u7981\u6b62\u4e24\u4e2a\u4e0b\u5212\u7ebf\u4e2d\u95f4\u53ea\n\n  \u51fa\u73b0\u6570\u5b57\u3002\u6570\u636e\u5e93\u5b57\u6bb5\u540d\u7684\u4fee\u6539\u4ee3\u4ef7\u5f88\u5927\uff0c\u56e0\u4e3a\u65e0\u6cd5\u8fdb\u884c\u9884\u53d1\u5e03\uff0c\u6240\u4ee5\u5b57\u6bb5\u540d\u79f0\u9700\u8981\u614e\u91cd\u8003\u8651\u3002\n\n  \u6b63\u4f8b\uff1agetter_admin\uff0ctask_config\uff0clevel3_name\n\n  \u53cd\u4f8b\uff1aGetterAdmin\uff0ctaskConfig\uff0clevel_3_name\n\n3. \u3010\u5f3a\u5236\u3011\u8868\u540d\u4e0d\u4f7f\u7528\u590d\u6570\u540d\u8bcd\u3002\n\n  \u8bf4\u660e\uff1a\u8868\u540d\u5e94\u8be5\u4ec5\u4ec5\u8868\u793a\u8868\u91cc\u9762\u7684\u5b9e\u4f53\u5185\u5bb9\uff0c\u4e0d\u5e94\u8be5\u8868\u793a\u5b9e\u4f53\u6570\u91cf\uff0c\u5bf9\u5e94\u4e8eDO\u7c7b\u540d\u4e5f\u662f\u5355\u6570\n\n  \u5f62\u5f0f\uff0c\u7b26\u5408\u8868\u8fbe\u4e60\u60ef\u3002\n\n4. \u3010\u5f3a\u5236\u3011\u7981\u7528\u4fdd\u7559\u5b57\uff0c\u5982desc\u3001range\u3001match\u3001delayed\u7b49\uff0c\u53c2\u8003\u5b98\u65b9\u4fdd\u7559\u5b57\u3002\n\n5. \u3010\u5f3a\u5236\u3011\u552f\u4e00\u7d22\u5f15\u540d\u4e3auk_\u5b57\u6bb5\u540d\uff1b\u666e\u901a\u7d22\u5f15\u540d\u5219\u4e3aidx_\u5b57\u6bb5\u540d\u3002\n\n  \u8bf4\u660e\uff1auk_\u5373 unique key\uff1bidx_\u5373index\u7684\u7b80\u79f0\u3002\n\n6. \u3010\u5f3a\u5236\u3011\u5c0f\u6570\u7c7b\u578b\u4e3adecimal\uff0c\u7981\u6b62\u4f7f\u7528float\u548cdouble\u3002\n\n  \u8bf4\u660e\uff1afloat\u548cdouble\u5728\u5b58\u50a8\u7684\u65f6\u5019\uff0c\u5b58\u5728\u7cbe\u5ea6\u635f\u5931\u7684\u95ee\u9898\uff0c\u5f88\u53ef\u80fd\u5728\u503c\u7684\u6bd4\u8f83\u65f6\uff0c\u5f97\u5230\u4e0d\n\n  \u6b63\u786e\u7684\u7ed3\u679c\u3002\u5982\u679c\u5b58\u50a8\u7684\u6570\u636e\u8303\u56f4\u8d85\u8fc7decimal\u7684\u8303\u56f4\uff0c\u5efa\u8bae\u5c06\u6570\u636e\u62c6\u6210\u6574\u6570\u548c\u5c0f\u6570\u5206\u5f00\u5b58\u50a8\u3002\n\n7. \u3010\u5f3a\u5236\u3011\u5982\u679c\u5b58\u50a8\u7684\u5b57\u7b26\u4e32\u957f\u5ea6\u51e0\u4e4e\u76f8\u7b49\uff0c\u4f7f\u7528CHAR\u5b9a\u957f\u5b57\u7b26\u4e32\u7c7b\u578b\u3002\n\n8. \u3010\u5f3a\u5236\u3011varchar\u662f\u53ef\u53d8\u957f\u5b57\u7b26\u4e32\uff0c\u4e0d\u9884\u5148\u5206\u914d\u5b58\u50a8\u7a7a\u95f4\uff0c\u957f\u5ea6\u4e0d\u8981\u8d85\u8fc75000\uff0c\u5982\u679c\u5b58\u50a8\u957f\u5ea6\n\n  \u5927\u4e8e\u6b64\u503c\uff0c\u5b9a\u4e49\u5b57\u6bb5\u7c7b\u578b\u4e3aTEXT\uff0c\u72ec\u7acb\u51fa\u6765\u4e00\u5f20\u8868\uff0c\u7528\u4e3b\u952e\u6765\u5bf9\u5e94\uff0c\u907f\u514d\u5f71\u54cd\u5176\u5b83\u5b57\u6bb5\u7d22\u5f15\n\n  \u6548\u7387\u3002\n\n9. \u3010\u5f3a\u5236\u3011\u8868\u5fc5\u5907\u4e09\u5b57\u6bb5\uff1aid, gmt_create, gmt_modified\u3002\n\n  \u8bf4\u660e\uff1a\u5176\u4e2did\u5fc5\u4e3a\u4e3b\u952e\uff0c\u7c7b\u578b\u4e3aunsigned bigint\u3001\u5355\u8868\u65f6\u81ea\u589e\u3001\u6b65\u957f\u4e3a1\uff1b\u5206\u8868\u65f6\u6539\u4e3a\u4ece\n\n      TDDL Sequence\u53d6\u503c\uff0c\u786e\u4fdd\u5206\u8868\u4e4b\u95f4\u7684\u5168\u5c40\u552f\u4e00\u3002gmt_create,gmt_modified\u7684\u7c7b\u578b\u5747\u4e3a\n\n      date_time\u7c7b\u578b\u3002\n\n10.\u3010\u63a8\u8350\u3011\u8868\u7684\u547d\u540d\u6700\u597d\u662f\u52a0\u4e0a&ldquo;\u4e1a\u52a1\u540d\u79f0_\u8868\u7684\u4f5c\u7528&rdquo;\uff0c\u907f\u514d\u4e0a\u4e91\u68af\u540e\uff0c\u518d\u4e0e\u5176\u5b83\u4e1a\u52a1\u8868\u5173\u8054\n\n  \u65f6\u6709\u6df7\u6dc6\u3002\n\n  \u6b63\u4f8b\uff1atiger_task \/ tiger_reader \/ mpp_config\n\n11.\u3010\u63a8\u8350\u3011\u5e93\u540d\u4e0e\u5e94\u7528\u540d\u79f0\u5c3d\u91cf\u4e00\u81f4\u3002\n\n12.\u3010\u63a8\u8350\u3011\u5982\u679c\u4fee\u6539\u5b57\u6bb5\u542b\u4e49\u6216\u5bf9\u5b57\u6bb5\u8868\u793a\u7684\u72b6\u6001\u8ffd\u52a0\u65f6\uff0c\u9700\u8981\u53ca\u65f6\u66f4\u65b0\u5b57\u6bb5\u6ce8\u91ca\u3002\n\n13.\u3010\u63a8\u8350\u3011\u5b57\u6bb5\u5141\u8bb8\u9002\u5f53\u5197\u4f59\uff0c\u4ee5\u63d0\u9ad8\u6027\u80fd\uff0c\u4f46\u662f\u5fc5\u987b\u8003\u8651\u6570\u636e\u540c\u6b65\u7684\u60c5\u51b5\u3002\u5197\u4f59\u5b57\u6bb5\u5e94\u9075\u5faa\uff1a\n\n1\uff09\u4e0d\u662f\u9891\u7e41\u4fee\u6539\u7684\u5b57\u6bb5\u3002\n\n2\uff09\u4e0d\u662fvarchar\u8d85\u957f\u5b57\u6bb5\uff0c\u66f4\u4e0d\u80fd\u662ftext\u5b57\u6bb5\u3002\n\n  \u6b63\u4f8b\uff1a\u5404\u4e1a\u52a1\u7ebf\u7ecf\u5e38\u5197\u4f59\u5b58\u50a8\u5546\u54c1\u540d\u79f0\uff0c\u907f\u514d\u67e5\u8be2\u65f6\u9700\u8981\u8c03\u7528IC\u670d\u52a1\u83b7\u53d6\u3002\n\n14.\u3010\u63a8\u8350\u3011\u5355\u8868\u884c\u6570\u8d85\u8fc7500\u4e07\u884c\u6216\u8005\u5355\u8868\u5bb9\u91cf\u8d85\u8fc72GB\uff0c\u624d\u63a8\u8350\u8fdb\u884c\u5206\u5e93\u5206\u8868\u3002\n\n  \u8bf4\u660e\uff1a\u5982\u679c\u9884\u8ba1\u4e09\u5e74\u540e\u7684\u6570\u636e\u91cf\u6839\u672c\u8fbe\u4e0d\u5230\u8fd9\u4e2a\u7ea7\u522b\uff0c\u8bf7\u4e0d\u8981\u5728\u521b\u5efa\u8868\u65f6\u5c31\u5206\u5e93\u5206\u8868\u3002\n\n  \u53cd\u4f8b\uff1a\u67d0\u4e1a\u52a1\u4e09\u5e74\u603b\u6570\u636e\u91cf\u624d2\u4e07\u884c\uff0c\u5374\u5206\u62101024\u5f20\u8868\uff0c\u95ee\uff1a\u4f60\u4e3a\u4ec0\u4e48\u8fd9\u4e48\u8bbe\u8ba1\uff1f\u7b54\uff1a\u52061024\n\n  \u5f20\u8868\uff0c\u4e0d\u662f\u6807\u914d\u5417\uff1f\n\n15.\u3010\u53c2\u8003\u3011\u5408\u9002\u7684\u5b57\u7b26\u5b58\u50a8\u957f\u5ea6\uff0c\u4e0d\u4f46\u8282\u7ea6\u6570\u636e\u5e93\u8868\u7a7a\u95f4\u3001\u8282\u7ea6\u7d22\u5f15\u5b58\u50a8\uff0c\u66f4\u91cd\u8981\u7684\u662f\u63d0\u5347\u68c0\u7d22\n\n  \u901f\u5ea6\u3002\n\n  \u6b63\u4f8b\uff1a\u4eba\u7684\u5e74\u9f84\u7528unsignedtinyint\uff08\u8868\u793a\u8303\u56f40-255\uff0c\u4eba\u7684\u5bff\u547d\u4e0d\u4f1a\u8d85\u8fc7255\u5c81\uff09\uff1b\u6d77\u9f9f\u5c31\n\n  \u5fc5\u987b\u662fsmallint\uff0c\u4f46\u5982\u679c\u662f\u592a\u9633\u7684\u5e74\u9f84\uff0c\u5c31\u5fc5\u987b\u662fint\uff1b\u5982\u679c\u662f\u6240\u6709\u6052\u661f\u7684\u5e74\u9f84\u90fd\u52a0\u8d77\u6765\uff0c\u90a3\n\n  \u4e48\u5c31\u5fc5\u987b\u4f7f\u7528bigint\u3002\n<\/pre>\n<\/div>\n<ul>\n<li>\u3000\u3000\u7d22\u5f15\u89c4\u7ea6<\/li>\n<\/ul>\n<div class=\"cnblogs_Highlighter\">\n<pre class=\"brush:bash;gutter:true;\">1. \u3010\u5f3a\u5236\u3011\u4e1a\u52a1\u4e0a\u5177\u6709\u552f\u4e00\u7279\u6027\u7684\u5b57\u6bb5\uff0c\u5373\u4f7f\u662f\u7ec4\u5408\u5b57\u6bb5\uff0c\u4e5f\u5fc5\u987b\u5efa\u6210\u552f\u4e00\u7d22\u5f15\u3002\n\n  \u8bf4\u660e\uff1a\u4e0d\u8981\u4ee5\u4e3a\u552f\u4e00\u7d22\u5f15\u5f71\u54cd\u4e86insert\u901f\u5ea6\uff0c\u8fd9\u4e2a\u901f\u5ea6\u635f\u8017\u53ef\u4ee5\u5ffd\u7565\uff0c\u4f46\u63d0\u9ad8\u67e5\u627e\u901f\u5ea6\u662f\u660e\n\n  \u663e\u7684\uff1b\u53e6\u5916\uff0c\u5373\u4f7f\u5728\u5e94\u7528\u5c42\u505a\u4e86\u975e\u5e38\u5b8c\u5584\u7684\u6821\u9a8c\u548c\u63a7\u5236\uff0c\u53ea\u8981\u6ca1\u6709\u552f\u4e00\u7d22\u5f15\uff0c\u6839\u636e\u58a8\u83f2\u5b9a\u5f8b\uff0c\n\n  \u5fc5\u7136\u6709\u810f\u6570\u636e\u4ea7\u751f\u3002\n\n2. \u3010\u5f3a\u5236\u3011\u8d85\u8fc7\u4e09\u4e2a\u8868\u7981\u6b62join\u3002\u9700\u8981join\u7684\u5b57\u6bb5\uff0c\u6570\u636e\u7c7b\u578b\u4fdd\u6301\u7edd\u5bf9\u4e00\u81f4\uff1b\u591a\u8868\u5173\u8054\u67e5\u8be2\u65f6\uff0c\n\n  \u4fdd\u8bc1\u88ab\u5173\u8054\u7684\u5b57\u6bb5\u9700\u8981\u6709\u7d22\u5f15\u3002\n\n  \u8bf4\u660e\uff1a\u5373\u4f7f\u53cc\u8868join\u4e5f\u8981\u6ce8\u610f\u8868\u7d22\u5f15\u3001SQL\u6027\u80fd\u3002\n\n3. \u3010\u5f3a\u5236\u3011\u5728varchar\u5b57\u6bb5\u4e0a\u5efa\u7acb\u7d22\u5f15\u65f6\uff0c\u5fc5\u987b\u6307\u5b9a\u7d22\u5f15\u957f\u5ea6\uff0c\u6ca1\u5fc5\u8981\u5bf9\u5168\u5b57\u6bb5\u5efa\u7acb\u7d22\u5f15\uff0c\u6839\u636e\n\n  \u5b9e\u9645\u6587\u672c\u533a\u5206\u5ea6\u51b3\u5b9a\u7d22\u5f15\u957f\u5ea6\u3002\n\n  \u8bf4\u660e\uff1a\u7d22\u5f15\u7684\u957f\u5ea6\u4e0e\u533a\u5206\u5ea6\u662f\u4e00\u5bf9\u77db\u76fe\u4f53\uff0c\u4e00\u822c\u5bf9\u5b57\u7b26\u4e32\u7c7b\u578b\u6570\u636e\uff0c\u957f\u5ea6\u4e3a20\u7684\u7d22\u5f15\uff0c\u533a\u5206\n\n  \u5ea6\u4f1a\u9ad8\u8fbe90%\u4ee5\u4e0a\uff0c\u53ef\u4ee5\u4f7f\u7528count(distinct left(\u5217\u540d,\u7d22\u5f15\u957f\u5ea6))\/count(*)\u7684\u533a\u5206\u5ea6\u6765\n\n  \u786e\u5b9a\u3002\n\n4. \u3010\u5f3a\u5236\u3011\u9875\u9762\u641c\u7d22\u4e25\u7981\u5de6\u6a21\u7cca\u6216\u8005\u5168\u6a21\u7cca\uff0c\u5982\u679c\u9700\u8981\u8bf7\u8d70\u641c\u7d22\u5f15\u64ce\u6765\u89e3\u51b3\u3002\n\n  \u8bf4\u660e\uff1a\u7d22\u5f15\u6587\u4ef6\u5177\u6709B-Tree\u7684\u6700\u5de6\u524d\u7f00\u5339\u914d\u7279\u6027\uff0c\u5982\u679c\u5de6\u8fb9\u7684\u503c\u672a\u786e\u5b9a\uff0c\u90a3\u4e48\u65e0\u6cd5\u4f7f\u7528\u6b64\u7d22\n\n  \u5f15\u3002\n\n5. \u3010\u63a8\u8350\u3011\u5982\u679c\u6709order by\u7684\u573a\u666f\uff0c\u8bf7\u6ce8\u610f\u5229\u7528\u7d22\u5f15\u7684\u6709\u5e8f\u6027\u3002order by \u6700\u540e\u7684\u5b57\u6bb5\u662f\u7ec4\u5408\u7d22\n\n  \u5f15\u7684\u4e00\u90e8\u5206\uff0c\u5e76\u4e14\u653e\u5728\u7d22\u5f15\u7ec4\u5408\u987a\u5e8f\u7684\u6700\u540e\uff0c\u907f\u514d\u51fa\u73b0file_sort\u7684\u60c5\u51b5\uff0c\u5f71\u54cd\u67e5\u8be2\u6027\u80fd\u3002\n\n  \u6b63\u4f8b\uff1awhere a=? and b=? order by c; \u7d22\u5f15\uff1aa_b_c\n\n  \u53cd\u4f8b\uff1a\u7d22\u5f15\u4e2d\u6709\u8303\u56f4\u67e5\u627e\uff0c\u90a3\u4e48\u7d22\u5f15\u6709\u5e8f\u6027\u65e0\u6cd5\u5229\u7528\uff0c\u5982\uff1aWHERE a&gt;10 ORDER BY b; \u7d22\u5f15a_b\n\n  \u65e0\u6cd5\u6392\u5e8f\u3002\n\n6. \u3010\u63a8\u8350\u3011\u5229\u7528\u8986\u76d6\u7d22\u5f15\u6765\u8fdb\u884c\u67e5\u8be2\u64cd\u4f5c\uff0c\u6765\u907f\u514d\u56de\u8868\u64cd\u4f5c\u3002\n\n  \u8bf4\u660e\uff1a\u5982\u679c\u4e00\u672c\u4e66\u9700\u8981\u77e5\u9053\u7b2c11\u7ae0\u662f\u4ec0\u4e48\u6807\u9898\uff0c\u4f1a\u7ffb\u5f00\u7b2c11\u7ae0\u5bf9\u5e94\u7684\u90a3\u4e00\u9875\u5417\uff1f\u76ee\u5f55\u6d4f\u89c8\u4e00\n\n  \u4e0b\u5c31\u597d\uff0c\u8fd9\u4e2a\u76ee\u5f55\u5c31\u662f\u8d77\u5230\u8986\u76d6\u7d22\u5f15\u7684\u4f5c\u7528\u3002\n\n  \u6b63\u4f8b\uff1aIDB\u80fd\u591f\u5efa\u7acb\u7d22\u5f15\u7684\u79cd\u7c7b\uff1a\u4e3b\u952e\u7d22\u5f15\u3001\u552f\u4e00\u7d22\u5f15\u3001\u666e\u901a\u7d22\u5f15\uff0c\u800c\u8986\u76d6\u7d22\u5f15\u662f\u4e00\u79cd\u67e5\u8be2\u7684\n\n  \u4e00\u79cd\u6548\u679c\uff0c\u7528explain\u7684\u7ed3\u679c\uff0cextra\u5217\u4f1a\u51fa\u73b0\uff1ausing index.\n\n7. \u3010\u63a8\u8350\u3011\u5229\u7528\u5ef6\u8fdf\u5173\u8054\u6216\u8005\u5b50\u67e5\u8be2\u4f18\u5316\u8d85\u591a\u5206\u9875\u573a\u666f\u3002\n\n  \u8bf4\u660e\uff1aMySQL\u5e76\u4e0d\u662f\u8df3\u8fc7offset\u884c\uff0c\u800c\u662f\u53d6offset+N\u884c\uff0c\u7136\u540e\u8fd4\u56de\u653e\u5f03\u524doffset\u884c\uff0c\u8fd4\u56deN\n\n  \u884c\uff0c\u90a3\u5f53offset\u7279\u522b\u5927\u7684\u65f6\u5019\uff0c\u6548\u7387\u5c31\u975e\u5e38\u7684\u4f4e\u4e0b\uff0c\u8981\u4e48\u63a7\u5236\u8fd4\u56de\u7684\u603b\u9875\u6570\uff0c\u8981\u4e48\u5bf9\u8d85\u8fc7\u7279\n\n  \u5b9a\u9608\u503c\u7684\u9875\u6570\u8fdb\u884cSQL\u6539\u5199\u3002\n\n  \u6b63\u4f8b\uff1a\u5148\u5feb\u901f\u5b9a\u4f4d\u9700\u8981\u83b7\u53d6\u7684id\u6bb5\uff0c\u7136\u540e\u518d\u5173\u8054\uff1a\n\n      SELECT a.* FROM \u88681a, (selectid from \u88681 where \u6761\u4ef6 LIMIT 100000,20 ) b where a.id=b.id\n\n8. \u3010\u63a8\u8350\u3011SQL\u6027\u80fd\u4f18\u5316\u7684\u76ee\u6807\uff1a\u81f3\u5c11\u8981\u8fbe\u5230 range\u7ea7\u522b\uff0c\u8981\u6c42\u662fref\u7ea7\u522b\uff0c\u5982\u679c\u53ef\u4ee5\u662fconsts\n\n  \u6700\u597d\u3002\n\n  \u8bf4\u660e\uff1a\n\n  1\uff09consts\u5355\u8868\u4e2d\u6700\u591a\u53ea\u6709\u4e00\u4e2a\u5339\u914d\u884c\uff08\u4e3b\u952e\u6216\u8005\u552f\u4e00\u7d22\u5f15\uff09\uff0c\u5728\u4f18\u5316\u9636\u6bb5\u5373\u53ef\u8bfb\u53d6\u5230\u6570\u636e\u3002\n\n  2\uff09ref\u6307\u7684\u662f\u4f7f\u7528\u666e\u901a\u7684\u7d22\u5f15\u3002\uff08normal index\uff09\n\n  3\uff09range\u5bf9\u7d22\u5f15\u8fdb\u8303\u56f4\u68c0\u7d22\u3002\n\n  \u53cd\u4f8b\uff1aexplain\u8868\u7684\u7ed3\u679c\uff0ctype=index\uff0c\u7d22\u5f15\u7269\u7406\u6587\u4ef6\u5168\u626b\u63cf\uff0c\u901f\u5ea6\u975e\u5e38\u6162\uff0c\u8fd9\u4e2aindex\u7ea7\u522b\n\n  \u6bd4\u8f83range\u8fd8\u4f4e\uff0c\u4e0e\u5168\u8868\u626b\u63cf\u662f\u5c0f\u5deb\u89c1\u5927\u5deb\u3002\n\n9. \u3010\u63a8\u8350\u3011\u5efa\u7ec4\u5408\u7d22\u5f15\u7684\u65f6\u5019\uff0c\u533a\u5206\u5ea6\u6700\u9ad8\u7684\u5728\u6700\u5de6\u8fb9\u3002\n\n  \u6b63\u4f8b\uff1a\u5982\u679cwherea=?andb=? \uff0ca\u5217\u7684\u51e0\u4e4e\u63a5\u8fd1\u4e8e\u552f\u4e00\u503c\uff0c\u90a3\u4e48\u53ea\u9700\u8981\u5355\u5efaidx_a\u7d22\u5f15\u5373\u53ef\u3002\n\n  \u8bf4\u660e\uff1a\u5b58\u5728\u975e\u7b49\u53f7\u548c\u7b49\u53f7\u6df7\u5408\u5224\u65ad\u6761\u4ef6\u65f6\uff0c\u5728\u5efa\u7d22\u5f15\u65f6\uff0c\u8bf7\u628a\u7b49\u53f7\u6761\u4ef6\u7684\u5217\u524d\u7f6e\u3002\u5982\uff1awherea&gt;?\n\n      and b=? \u90a3\u4e48\u5373\u4f7fa\u7684\u533a\u5206\u5ea6\u66f4\u9ad8\uff0c\u4e5f\u5fc5\u987b\u628ab\u653e\u5728\u7d22\u5f15\u7684\u6700\u524d\u5217\u3002\n\n10.\u3010\u53c2\u8003\u3011\u521b\u5efa\u7d22\u5f15\u65f6\u907f\u514d\u6709\u5982\u4e0b\u6781\u7aef\u8bef\u89e3\uff1a\n\n  1\uff09\u8bef\u8ba4\u4e3a\u4e00\u4e2a\u67e5\u8be2\u5c31\u9700\u8981\u5efa\u4e00\u4e2a\u7d22\u5f15\u3002\n\n  2\uff09\u8bef\u8ba4\u4e3a\u7d22\u5f15\u4f1a\u6d88\u8017\u7a7a\u95f4\u3001\u4e25\u91cd\u62d6\u6162\u66f4\u65b0\u548c\u65b0\u589e\u901f\u5ea6\u3002\n\n  3\uff09\u8bef\u8ba4\u4e3a\u552f\u4e00\u7d22\u5f15\u4e00\u5f8b\u9700\u8981\u5728\u5e94\u7528\u5c42\u901a\u8fc7&ldquo;\u5148\u67e5\u540e\u63d2&rdquo;\u65b9\u5f0f\u89e3\u51b3\u3002\n<\/pre>\n<\/div>\n<ul>\n<li>\u3000\u3000SQL\u89c4\u7ea6<\/li>\n<\/ul>\n<div class=\"cnblogs_Highlighter\">\n<pre class=\"brush:bash;gutter:true;\">1. \u3010\u5f3a\u5236\u3011\u4e0d\u8981\u4f7f\u7528count(\u5217\u540d)\u6216count(\u5e38\u91cf)\u6765\u66ff\u4ee3count(*)\uff0ccount(*)\u5c31\u662fSQL92\u5b9a\u4e49\u7684\n\n  \u6807\u51c6\u7edf\u8ba1\u884c\u6570\u7684\u8bed\u6cd5\uff0c\u8ddf\u6570\u636e\u5e93\u65e0\u5173\uff0c\u8ddfNULL\u548c\u975eNULL\u65e0\u5173\u3002\n\n  \u8bf4\u660e\uff1acount(*)\u4f1a\u7edf\u8ba1\u503c\u4e3aNULL\u7684\u884c\uff0c\u800ccount(\u5217\u540d)\u4e0d\u4f1a\u7edf\u8ba1\u6b64\u5217\u4e3aNULL\u503c\u7684\u884c\u3002\n\n2. \u3010\u5f3a\u5236\u3011count(distinct col) \u8ba1\u7b97\u8be5\u5217\u9664NULL\u4e4b\u5916\u7684\u4e0d\u91cd\u590d\u6570\u91cf\u3002\u6ce8\u610f count(distinct\n\n      col1, col2) \u5982\u679c\u5176\u4e2d\u4e00\u5217\u5168\u4e3aNULL\uff0c\u90a3\u4e48\u5373\u4f7f\u53e6\u4e00\u5217\u6709\u4e0d\u540c\u7684\u503c\uff0c\u4e5f\u8fd4\u56de\u4e3a0\u3002\n\n3. \u3010\u5f3a\u5236\u3011\u5f53\u67d0\u4e00\u5217\u7684\u503c\u5168\u662fNULL\u65f6\uff0ccount(col)\u7684\u8fd4\u56de\u7ed3\u679c\u4e3a0\uff0c\u4f46sum(col)\u7684\u8fd4\u56de\u7ed3\u679c\u4e3a\n\n     NULL\uff0c\u56e0\u6b64\u4f7f\u7528sum()\u65f6\u9700\u6ce8\u610fNPE\u95ee\u9898\u3002\n\n  \u6b63\u4f8b\uff1a\u53ef\u4ee5\u4f7f\u7528\u5982\u4e0b\u65b9\u5f0f\u6765\u907f\u514dsum\u7684NPE\u95ee\u9898\uff1aSELECTIF(ISNULL(SUM(g)),0,SUM(g))FROM\n\n     table;\n\n4. \u3010\u5f3a\u5236\u3011\u4f7f\u7528ISNULL()\u6765\u5224\u65ad\u662f\u5426\u4e3aNULL\u503c\u3002\u6ce8\u610f\uff1aNULL\u4e0e\u4efb\u4f55\u503c\u7684\u76f4\u63a5\u6bd4\u8f83\u90fd\u4e3aNULL\u3002\n\n  \u8bf4\u660e\uff1a\n\n  1\uff09 NULL&lt;&gt;NULL\u7684\u8fd4\u56de\u7ed3\u679c\u662fNULL\uff0c\u4e0d\u662ffalse\u3002\n\n  2\uff09 NULL=NULL\u7684\u8fd4\u56de\u7ed3\u679c\u662fNULL\uff0c\u4e0d\u662ftrue\u3002\n\n  3\uff09 NULL&lt;&gt;1\u7684\u8fd4\u56de\u7ed3\u679c\u662fNULL\uff0c\u800c\u4e0d\u662ftrue\u3002\n\n5. \u3010\u5f3a\u5236\u3011\u5728\u4ee3\u7801\u4e2d\u5199\u5206\u9875\u67e5\u8be2\u903b\u8f91\u65f6\uff0c\u82e5count\u4e3a0\u5e94\u76f4\u63a5\u8fd4\u56de\uff0c\u907f\u514d\u6267\u884c\u540e\u9762\u7684\u5206\u9875\u8bed\u53e5\u3002\n\n6. \u3010\u5f3a\u5236\u3011\u4e0d\u5f97\u4f7f\u7528\u5916\u952e\u4e0e\u7ea7\u8054\uff0c\u4e00\u5207\u5916\u952e\u6982\u5ff5\u5fc5\u987b\u5728\u5e94\u7528\u5c42\u89e3\u51b3\u3002\n\n  \u8bf4\u660e\uff1a\uff08\u6982\u5ff5\u89e3\u91ca\uff09\u5b66\u751f\u8868\u4e2d\u7684student_id\u662f\u4e3b\u952e\uff0c\u90a3\u4e48\u6210\u7ee9\u8868\u4e2d\u7684student_id\u5219\u4e3a\u5916\u952e\u3002\n\n  \u5982\u679c\u66f4\u65b0\u5b66\u751f\u8868\u4e2d\u7684student_id\uff0c\u540c\u65f6\u89e6\u53d1\u6210\u7ee9\u8868\u4e2d\u7684student_id\u66f4\u65b0\uff0c\u5219\u4e3a\u7ea7\u8054\u66f4\u65b0\u3002\u5916\n\n  \u952e\u4e0e\u7ea7\u8054\u66f4\u65b0\u9002\u7528\u4e8e\u5355\u673a\u4f4e\u5e76\u53d1\uff0c\u4e0d\u9002\u5408\u5206\u5e03\u5f0f\u3001\u9ad8\u5e76\u53d1\u96c6\u7fa4\uff1b\u7ea7\u8054\u66f4\u65b0\u662f\u5f3a\u963b\u585e\uff0c\u5b58\u5728\u6570\u636e\n\n  \u5e93\u66f4\u65b0\u98ce\u66b4\u7684\u98ce\u9669\uff1b\u5916\u952e\u5f71\u54cd\u6570\u636e\u5e93\u7684\u63d2\u5165\u901f\u5ea6\u3002\n\n7. \u3010\u5f3a\u5236\u3011\u7981\u6b62\u4f7f\u7528\u5b58\u50a8\u8fc7\u7a0b\uff0c\u5b58\u50a8\u8fc7\u7a0b\u96be\u4ee5\u8c03\u8bd5\u548c\u6269\u5c55\uff0c\u66f4\u6ca1\u6709\u79fb\u690d\u6027\u3002\n\n8. \u3010\u5f3a\u5236\u3011IDB\u6570\u636e\u8ba2\u6b63\u65f6\uff0c\u5220\u9664\u548c\u4fee\u6539\u8bb0\u5f55\u65f6\uff0c\u8981\u5148select\uff0c\u907f\u514d\u51fa\u73b0\u8bef\u5220\u9664\uff0c\u786e\u8ba4\u65e0\u8bef\u624d\u80fd\n\n  \u63d0\u4ea4\u6267\u884c\u3002\n\n9. \u3010\u63a8\u8350\u3011in\u64cd\u4f5c\u80fd\u907f\u514d\u5219\u907f\u514d\uff0c\u82e5\u5b9e\u5728\u907f\u514d\u4e0d\u4e86\uff0c\u9700\u8981\u4ed4\u7ec6\u8bc4\u4f30in\u540e\u8fb9\u7684\u96c6\u5408\u5143\u7d20\u6570\u91cf\uff0c\u63a7\n\n  \u5236\u57281000\u4e2a\u4e4b\u5185\u3002\n\n10.\u3010\u53c2\u8003\u3011\u56e0\u963f\u91cc\u5df4\u5df4\u5168\u7403\u5316\u9700\u8981\uff0c\u6240\u6709\u7684\u5b57\u7b26\u5b58\u50a8\u4e0e\u8868\u793a\uff0c\u5747\u4ee5utf-8\u7f16\u7801\uff0c\u90a3\u4e48\u5b57\u7b26\u8ba1\u6570\u65b9\n\n  \u6cd5\u6ce8\u610f\uff1a\n\n  \u8bf4\u660e\uff1a\n\n      SELECT LENGTH(\"\u963f\u91cc\u5df4\u5df4\")\uff1b \u8fd4\u56de\u4e3a12\n\n      SELECT CHARACTER_LENGTH(\"\u963f\u91cc\u5df4\u5df4\")\uff1b \u8fd4\u56de\u4e3a4\n\n  \u5982\u679c\u8981\u4f7f\u7528\u8868\u60c5\uff0c\u90a3\u4e48\u4f7f\u7528utfmb4\u6765\u8fdb\u884c\u5b58\u50a8\uff0c\u6ce8\u610f\u5b83\u4e0eutf-8\u7f16\u7801\u3002\n\n11.\u3010\u53c2\u8003\u3011TRUNCATE TABLE \u6bd4 DELETE\u901f\u5ea6\u5feb\uff0c\u4e14\u4f7f\u7528\u7684\u7cfb\u7edf\u548c\u4e8b\u52a1\u65e5\u5fd7\u8d44\u6e90\u5c11\uff0c\u4f46TRUNCATE\n\n  \u65e0\u4e8b\u52a1\u4e14\u4e0d\u89e6\u53d1trigger\uff0c\u6709\u53ef\u80fd\u9020\u6210\u4e8b\u6545\uff0c\u6545\u4e0d\u5efa\u8bae\u5728\u5f00\u53d1\u4ee3\u7801\u4e2d\u4f7f\u7528\u6b64\u8bed\u53e5\u3002\n\n  \u8bf4\u660e\uff1aTRUNCATE TABLE \u5728\u529f\u80fd\u4e0a\u4e0e\u4e0d\u5e26 WHERE\u5b50\u53e5\u7684 DELETE\u8bed\u53e5\u76f8\u540c\u3002\n<\/pre>\n<\/div>\n<ul>\n<li>\u3000\u3000ORM\u89c4\u7ea6<\/li>\n<\/ul>\n<div class=\"cnblogs_Highlighter\">\n<pre class=\"brush:bash;gutter:true;\">1. \u3010\u5f3a\u5236\u3011\u5728\u8868\u67e5\u8be2\u4e2d\uff0c\u4e00\u5f8b\u4e0d\u8981\u4f7f\u7528 *\u4f5c\u4e3a\u67e5\u8be2\u7684\u5b57\u6bb5\u5217\u8868\uff0c\u9700\u8981\u54ea\u4e9b\u5b57\u6bb5\u5fc5\u987b\u660e\u786e\u5199\u660e\u3002\n\n  \u8bf4\u660e\uff1a1\uff09\u589e\u52a0\u67e5\u8be2\u5206\u6790\u5668\u89e3\u6790\u6210\u672c\u30022\uff09\u589e\u51cf\u5b57\u6bb5\u5bb9\u6613\u4e0eresultMap\u914d\u7f6e\u4e0d\u4e00\u81f4\u3002\n\n2. \u3010\u5f3a\u5236\u3011POJO\u7c7b\u7684boolean\u5c5e\u6027\u4e0d\u80fd\u52a0is\uff0c\u800c\u6570\u636e\u5e93\u5b57\u6bb5\u5fc5\u987b\u52a0is_\uff0c\u8981\u6c42\u5728resultMap\u4e2d\n\n  \u8fdb\u884c\u5b57\u6bb5\u4e0e\u5c5e\u6027\u4e4b\u95f4\u7684\u6620\u5c04\u3002\n\n  \u8bf4\u660e\uff1a\u53c2\u89c1\u5b9a\u4e49POJO\u7c7b\u4ee5\u53ca\u6570\u636e\u5e93\u5b57\u6bb5\u5b9a\u4e49\u89c4\u5b9a\uff0c\u5728sql.xml\u589e\u52a0\u6620\u5c04\uff0c\u662f\u5fc5\u987b\u7684\u3002\n\n3. \u3010\u5f3a\u5236\u3011\u4e0d\u8981\u7528resultClass\u5f53\u8fd4\u56de\u53c2\u6570\uff0c\u5373\u4f7f\u6240\u6709\u7c7b\u5c5e\u6027\u540d\u4e0e\u6570\u636e\u5e93\u5b57\u6bb5\u4e00\u4e00\u5bf9\u5e94\uff0c\u4e5f\u9700\u8981\n\n  \u5b9a\u4e49\uff1b\u53cd\u8fc7\u6765\uff0c\u6bcf\u4e00\u4e2a\u8868\u4e5f\u5fc5\u7136\u6709\u4e00\u4e2a\u4e0e\u4e4b\u5bf9\u5e94\u3002\n\n  \u8bf4\u660e\uff1a\u914d\u7f6e\u6620\u5c04\u5173\u7cfb\uff0c\u4f7f\u5b57\u6bb5\u4e0eDO\u7c7b\u89e3\u8026\uff0c\u65b9\u4fbf\u7ef4\u62a4\u3002\n\n4. \u3010\u5f3a\u5236\u3011xml\u914d\u7f6e\u4e2d\u53c2\u6570\u6ce8\u610f\u4f7f\u7528\uff1a#{}\uff0c#param#\u4e0d\u8981\u4f7f\u7528${}\u6b64\u79cd\u65b9\u5f0f\u5bb9\u6613\u51fa\u73b0SQL\u6ce8\u5165\u3002\n\n5. \u3010\u5f3a\u5236\u3011iBATIS\u81ea\u5e26\u7684queryForList(String statementName,int start,int size)\u4e0d\u63a8\u8350\u4f7f\n\n  \u7528\u3002\n\n  \u8bf4\u660e\uff1a\u5176\u5b9e\u73b0\u65b9\u5f0f\u662f\u5728\u6570\u636e\u5e93\u53d6\u5230statementName\u5bf9\u5e94\u7684SQL\u8bed\u53e5\u7684\u6240\u6709\u8bb0\u5f55\uff0c\u518d\u901a\u8fc7subList\n\n  \u53d6start,size\u7684\u5b50\u96c6\u5408\uff0c\u7ebf\u4e0a\u56e0\u4e3a\u8fd9\u4e2a\u539f\u56e0\u66fe\u7ecf\u51fa\u73b0\u8fc7OOM\u3002\n\n  \u6b63\u4f8b\uff1a\u5728sqlmap.xml\u4e2d\u5f15\u5165 #start#, #size#\n\n      Map&lt;String, Object&gt; map = new HashMap&lt;String,Object&gt;();\n\n      map.put(\"start\", start);\n\n      map.put(\"size\", size);\n\n6. \u3010\u5f3a\u5236\u3011\u4e0d\u5141\u8bb8\u76f4\u63a5\u62ffHashMap\u4e0eHashTable\u4f5c\u4e3a\u67e5\u8be2\u7ed3\u679c\u96c6\u7684\u8f93\u51fa\u3002\n\n  \u53cd\u4f8b\uff1a\u67d0\u540c\u5b66\u4e3a\u907f\u514d\u5199\u4e00\u4e2a&lt;resultMap&gt;\uff0c\u76f4\u63a5\u4f7f\u7528HashTable\u6765\u63a5\u6536\u6570\u636e\u5e93\u8fd4\u56de\u7ed3\u679c\uff0c\u7ed3\u679c\n\n  \u51fa\u73b0\u65e5\u5e38\u662f\u628abigint\u8f6c\u6210Long\u503c\uff0c\u800c\u7ebf\u4e0a\u7531\u4e8e\u6570\u636e\u5e93\u7248\u672c\u4e0d\u4e00\u6837\uff0c\u89e3\u6790\u6210BigInteger\uff0c\u5bfc\n\n  \u81f4\u7ebf\u4e0a\u95ee\u9898\u3002\n\n7. \u3010\u5f3a\u5236\u3011\u66f4\u65b0\u6570\u636e\u8868\u8bb0\u5f55\u65f6\uff0c\u5fc5\u987b\u540c\u65f6\u66f4\u65b0\u8bb0\u5f55\u5bf9\u5e94\u7684gmt_modified\u5b57\u6bb5\u503c\u4e3a\u5f53\u524d\u65f6\u95f4\u3002\n\n8. \u3010\u63a8\u8350\u3011\u4e0d\u8981\u5199\u4e00\u4e2a\u5927\u800c\u5168\u7684\u6570\u636e\u66f4\u65b0\u63a5\u53e3\uff0c\u4f20\u5165\u4e3aPOJO\u7c7b\uff0c\u4e0d\u7ba1\u662f\u4e0d\u662f\u81ea\u5df1\u7684\u76ee\u6807\u66f4\u65b0\u5b57\n\n  \u6bb5\uff0c\u90fd\u8fdb\u884cupdate table set c1=value1,c2=value2,c3=value3; \u8fd9\u662f\u4e0d\u5bf9\u7684\u3002\u6267\u884cSQL\u65f6\uff0c\n\n  \u5c3d\u91cf\u4e0d\u8981\u66f4\u65b0\u65e0\u6539\u52a8\u7684\u5b57\u6bb5\uff0c\u4e00\u662f\u6613\u51fa\u9519\uff1b\u4e8c\u662f\u6548\u7387\u4f4e\uff1b\u4e09\u662fbinlog\u589e\u52a0\u5b58\u50a8\u3002\n\n9. \u3010\u53c2\u8003\u3011@Transactional\u4e8b\u52a1\u4e0d\u8981\u6ee5\u7528\u3002\u4e8b\u52a1\u4f1a\u5f71\u54cd\u6570\u636e\u5e93\u7684QPS\uff0c\u53e6\u5916\u4f7f\u7528\u4e8b\u52a1\u7684\u5730\u65b9\u9700\u8981\n\n  \u8003\u8651\u5404\u65b9\u9762\u7684\u56de\u6eda\u65b9\u6848\uff0c\u5305\u62ec\u7f13\u5b58\u56de\u6eda\u3001\u641c\u7d22\u5f15\u64ce\u56de\u6eda\u3001\u6d88\u606f\u8865\u507f\u3001\u7edf\u8ba1\u4fee\u6b63\u7b49\u3002\n\n10.\u3010\u53c2\u8003\u3011&lt;isEqual&gt;\u4e2d\u7684compareValue\u662f\u4e0e\u5c5e\u6027\u503c\u5bf9\u6bd4\u7684\u5e38\u91cf\uff0c\u4e00\u822c\u662f\u6570\u5b57\uff0c\u8868\u793a\u76f8\u7b49\u65f6\u5e26\u4e0a\n\n  \u6b64\u6761\u4ef6\uff1b&lt;isNotEmpty&gt;\u8868\u793a\u4e0d\u4e3a\u7a7a\u4e14\u4e0d\u4e3anull\u65f6\u6267\u884c\uff1b&lt;isNotNull&gt;\u8868\u793a\u4e0d\u4e3anull\u503c\u65f6\u6267\u884c\u3002\n<\/pre>\n<\/div>\n<p>\u3000\u3000<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4e00\uff1a\u5efa\u8868\u89c4\u7ea6 &nbsp; 1. \u3010\u5f3a\u5236\u3011\u8868\u8fbe\u662f\u4e0e\u5426\u6982\u5ff5\u7684\u5b57\u6bb5\uff0c\u5fc5\u987b\u4f7f\u7528is_xxx\u7684\u65b9\u5f0f\u547d\u540d\uff0c\u6570\u636e\u7c7b\u578b\u662fun &hellip; <a href=\"http:\/\/blog.langmanezhuang.com\/index.php\/2021\/09\/13\/%e5%9f%ba%e4%ba%8e%e9%98%bf%e9%87%8c%e5%b7%b4%e5%b7%b4-mysql%e8%a7%84%e7%ba%a6-%e8%a7%84%e8%8c%83-%e6%80%bb%e7%bb%93\/\" class=\"more-link\">\u7ee7\u7eed\u9605\u8bfb <span class=\"screen-reader-text\">\u57fa\u4e8e\u963f\u91cc\u5df4\u5df4-Mysql\u89c4\u7ea6\/\u89c4\u8303 \u603b\u7ed3<\/span> <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"_links":{"self":[{"href":"http:\/\/blog.langmanezhuang.com\/index.php\/wp-json\/wp\/v2\/posts\/854"}],"collection":[{"href":"http:\/\/blog.langmanezhuang.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/blog.langmanezhuang.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/blog.langmanezhuang.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/blog.langmanezhuang.com\/index.php\/wp-json\/wp\/v2\/comments?post=854"}],"version-history":[{"count":0,"href":"http:\/\/blog.langmanezhuang.com\/index.php\/wp-json\/wp\/v2\/posts\/854\/revisions"}],"wp:attachment":[{"href":"http:\/\/blog.langmanezhuang.com\/index.php\/wp-json\/wp\/v2\/media?parent=854"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/blog.langmanezhuang.com\/index.php\/wp-json\/wp\/v2\/categories?post=854"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/blog.langmanezhuang.com\/index.php\/wp-json\/wp\/v2\/tags?post=854"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}