Oracle 的表的管理----表名和列的命名规则
Oracle 的表的管理----表名和列的命名规则 必须以字母开头 长度不能超过30个字符 不能使用Oracle的保留字 只能使用如下字符 A
Oracle 的表的管理----表名和列的命名规则
必须以字母开头
长度不能超过30个字符
不能使用Oracle的保留字
只能使用如下字符 A-Z，a-z,0-9,#$等
==========================================================
Oracle的数据类型
字符型
char 定长 最大2000字符 （char 查询的速度很快）
例子：char（10） ‘陈闯’前四个字符放‘陈闯’后面添6个空格补全
总结：如果你在知道字符长度的情况下建议用char，如身份证号 等，，因为char的查询速度很快
在数据库中时间和空间是不会同时满足的。
varchar2（20）变长 最大4000字符
例子:varchar(10) '陈闯' Oracle就会给分配四个字符
这样就可以节省空间
clob（character large objiect）字符型大对象 最大4G
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数字类型
number 范围 10 的-38次方到10 的38次方
number（5，2）
表示一个小数有5位有效数，2位小数
范围 -999.99- 999.99
number（5）
表示一个5位数
范围-999 99- 999 99
-----------------------------------------------------
日期类型
date包括年月日和时分秒
timestamp 是date的数据类型的扩展
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图片
blob 二进制数据， 可以存放图片、声音。 4G
注：
普通的视频声音文件存放在数据库中的是路径就可以了
保密的视频和声音文件要放在数据库中
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