一个mysql字段字符长度1000，不需要用于搜索，海量数据，把它设置为varchar好还是text好？-PHP Tutorial-php.cn

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一个mysql字段字符长度1000，不需要用于搜索，海量数据，把它设置为varchar好还是text好？

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Jun 06, 2016 pm 08:13 PM

mysqlphp

一个mysql字段最大字符长度1000，不需要用于搜索，记录条数可能过千万，将来可能会水平分表，把它设置为varchar好还是text好？需不需要先垂直分表？

回复内容：

一个mysql字段最大字符长度1000，不需要用于搜索，记录条数可能过千万，将来可能会水平分表，把它设置为varchar好还是text好？需不需要先垂直分表？

mysql的记录行长度是有限制的，不是无限长的，这个长度是64K，即65535个字节，对所有的表都是一样的。
MySQL对于变长类型的字段会有1-2个字节来保存字符长度。
当字符数小于等于255时，MySQL只用1个字节来记录，因为2的8次方减1只能存到255。
当字符数多余255时，就得用2个字节来存长度了。
在utf-8状态下的varchar，最大只能到 (65535 - 2) / 3 = 21844 余 1。
在gbk状态下的varchar, 最大只能到 (65535 - 2) / 2 = 32766 余 1

引用：https://ruby-china.org/topics/24920

1000这个长度很常见，大部分时候不需要分表。也不需要用text。直接用varchar就好。
在5.5以后的版本的mysql中，varchar不再有字段长度限制。但是需要注意的是，整行记录有65535字节的限制（是字节，不是字符。如果是UTF-8编码，单个字符可能占用2-3个字节）。

记录在千万级更是没问题了。读写十分频繁，性能十分严苛时，才考虑将这个字段分离出去。

VARCHAR() 最大255 只能存 text

一个mysql字段字符长度1000，不需要用于搜索，海量数据，把它设置为varchar好还是text好？

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