{"id":144,"date":"2017-04-07T08:27:16","date_gmt":"2017-04-07T00:27:16","guid":{"rendered":"http:\/\/www.jsjs.org\/?p=144"},"modified":"2017-04-07T08:27:16","modified_gmt":"2017-04-07T00:27:16","slug":"varcharn%e7%b1%bb%e5%9e%8b%ef%bc%8cutf8%e7%bc%96%e7%a0%81%ef%bc%8c%e5%88%99n%e6%9c%80%e5%a4%a7%e5%80%bc%e4%b8%ba%e5%a4%9a%e5%b0%91%ef%bc%8cn%e8%a1%a8%e7%a4%ba%e4%bb%80%e4%b9%88%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/blog.jsjs.org\/?p=144","title":{"rendered":"VARCHAR(N)\u7c7b\u578b\uff0cutf8\u7f16\u7801\uff0c\u5219N\u6700\u5927\u503c\u4e3a\u591a\u5c11\uff0cn\u8868\u793a\u4ec0\u4e48\uff1f"},"content":{"rendered":"

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\n\u5148\u660e\u767d\u8ba1\u7b97\u7684\u4e00\u4e9b\u89c4\u5219\u9650\u5236<\/strong><\/p>\n

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\n5.0\u7248\u672c\u4ee5\u4e0a\uff0cvarchar(20)\uff0c\u6307\u7684\u662f20\u5b57\u7b26<\/strong>\uff0c\u65e0\u8bba\u5b58\u653e\u7684\u662f\u6570\u5b57\u3001\u5b57\u6bcd\u8fd8\u662fUTF8\u6c49\u5b57\uff08\u6bcf\u4e2a\u6c49\u5b573\u5b57\u8282\uff09\uff0c\u90fd\u53ef\u4ee5\u5b58\u653e20\u4e2a\uff0c\u6700\u5927\u5927\u5c0f\u662f65532\u5b57\u8282<\/p>\n

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\n\u2462 \u957f\u5ea6\u9650\u5236
\nMySQL<\/a>\u5b9a\u4e49\u884c\u7684\u957f\u5ea6\u4e0d\u80fd\u8d85\u8fc765535\uff0c\u8fd9\u4e2a\u9650\u5236\u4e86\u5217\u7684\u6570\u76ee\uff0c\u6bd4\u5982char(255) utf8
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\nrow length = 1
\n+ (sum of column lengths)
\n+ (number of NULL columns + delete_flag + 7)\/8
\n+ (number of variable-length columns)
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\n\u51cf1\u662f\u56e0\u4e3a\u5b9e\u9645\u5b58\u50a8\u4ece\u7b2c2\u4e2a\u5b57\u8282\u5f00\u59cb
\n\u51cf2\u5219\u56e0\u4e3a\u8981\u5728\u5217\u8868\u957f\u5ea6\u5b58\u50a8\u5b9e\u9645\u5b57\u7b26\u957f\u5ea6
\n\u96643\u662f\u56e0\u4e3autf8\u7f16\u7801\u9650\u5236<\/p>\n

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\ncreate table t4(c int, c2 char(30), c3 varchar(N)) charset=utf8;
\nN\u7684\u6700\u5927\u503c\uff1a(65535-1-2-4-30*3)\/3<\/p>\n

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\u51cf1\u548c\u51cf2\u4e0e\u4e0a\u4f8b\u76f8\u540c;<\/p>\n

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[…]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center 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