mysql数据库实际存储的字符长度超过了varchar（M）的定义的长度,会怎么样?

理解确VARCHAR比CHAR存更内容

外CHAR定例定义字段类型CHAR(32)论存110字符数据库都配32字符空间

VARCHAR变定义VARCHAR(32)字段存1字符占1空间、存10占10空间浪费余空间

定处修改便查询便变修改麻烦指系统内部

备注：举例所说占用空间理论值事实需要配NULL标志空间、数据度空间至少要1～2字节

查询数据库中,表结构的详细信息 SELECT

表名=case when a.colorder=1 then d.name else '' end,

字段序号=a.colorder,

字段名=a.name,

标识=case when COLUMNPROPERTY( a.id,a.name,'IsIdentity')=1 then '√'else '' end,

主键=case when exists(SELECT 1 FROM sysobjects where xtype='PK' and name in (

SELECT name FROM sysindexes WHERE indid in(

SELECT indid FROM sysindexkeys WHERE id = a.id AND colid=a.colid

))) then '√' else '' end,

类型=b.name,

占用字节数=a.length,

长度=COLUMNPROPERTY(a.id,a.name,'PRECISION'),

小数位数=isnull(COLUMNPROPERTY(a.id,a.name,'Scale'),0),

允许空=case when a.isnullable=1 then '√'else '' end,

默认值=isnull(e.text,''),

字段说明=isnull(g.[value],'')

FROM syscolumns a

left join systypes b on a.xtype=b.xusertype

inner join sysobjects d on a.id=d.id and d.xtype='U' and d.name<>'dtproperties'

left join syscomments e on a.cdefault=e.id

left join sysproperties g on a.id=g.id and a.colid=g.smallid

order by a.id,a.colorder

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