mysql整型数据宽度，字段的零填充和符号

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mysql整型数据宽度，字段的零填充和符号_MySQL

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Jun 01, 2016 pm 01:41 PM

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bitsCN.com
mysql整型数据宽度，字段的零填充和符号 1.整型的符号在mysql中数字数据类型是有符号和无符号两种，当然整型也是，在定义一个字段的时候可以这么使用 age tinyint unsigned,unsigned代表是无符号，即都是大与等于0 的数如果这样使用是默认有符号的age tinyint ， 2.整型的数据宽度和零填充如下语句 age tinyint(1) , 代表age这个字段是1个字符宽度，但是如果不设置零填充式无效的，mysql将会忽略那个字符宽度。如下语句是有有效的 age tinyint(1) zerofill,只有在设置了零填充之后数据宽度才会有效，如果插入的数据时20将会插入出错。注意：zerofill的字段默认是无符号的，就是大于等于零的数据，输入小与零的数字将会报错。这个语句和上个语句是同一个意思：age tinyint（1） unsigned zerofill.还有一点注意的地方，最好为字段设置上默认值，要不然不容易比较在mysql中字段值是null时，和谁都能不能比较，甚至和null自己本身都不能比较，比较结果都是null。作者 com360 bitsCN.com

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