Sun, 05 Oct 2008 11:30:00 GMThttp://blog.csdn.net/marchonchina/http://blog.csdn.net/marchonchina/archive/2008/10/05/3017116.aspxhttp://blog.csdn.net/marchonchina/comments/3017116.aspx0http://blog.csdn.net/marchonchina/comments/commentRss/3017116.aspxhttp://tb.blog.csdn.net/TrackBack.aspx?PostId=3017116<P><FONT color=#ff6600>区别：</FONT> 　</P> <P>　1．CHAR的长度是固定的，而VARCHAR2的长度是可以变化的， 比如，存储字符串“abc"，对于CHAR (20)，表示你存储的字符将占20个字节(包括17个空字符)，而同样的VARCHAR2 (20)则只占用3个字节的长度，20只是最大值，当你存储的字符小于20时，按实际长度存储。 　　</P> <P>2．CHAR的效率比VARCHAR2的效率稍高。 　</P> <P>　3．目前VARCHAR是VARCHAR2的同义词。工业标准的VARCHAR类型可以存储空字符串，但是Oracle不这样做，尽管它保留以后这样做的权利。Oracle自己开发了一个数据类型VARCHAR2，这个类型不是一个标准的VARCHAR，它将在数据库中varchar列可以存储空字符串的特性改为存储<FONT color=#000000>NULL</FONT>值。假如你想有向后兼容的能力，Oracle建议使用VARCHAR2而不是VARCHAR。 　　</P> <P><FONT color=#ff6600>何时该用CH<img src ="http://blog.csdn.net/marchonchina/aggbug/3017116.aspx" width = "1" height = "1" />Sun, 05 Oct 2008 19:30:00 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