Re: mysql�е�key��ʲô��˼��

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1 total messages Started by Galaxy��VOLUNTEERS��Database Tue, 29 Dec 2009 08:18

#232

Author: Galaxy��VOLUNTEERS��Database
Date: Tue, 29 Dec 2009 08:18

24 lines
1998 bytes

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KEYͨ����INDEXͬ��ʡ����ؼ�������PRIMARY   KEY���ж������Ѹ���PRIMARY 
  KEYҲ����ָֻ��ΪKEY����ô����Ŀ������������ݿ�ϵͳ���ݡ� 

PRIMARY   KEY��һ��ΨһKEY����ʱ�����еĹؼ����б��붨��ΪNOT   NULL�������
Щ��û�б���ȷ�ض���ΪNOT   NULL��MySQLӦ�����ض�����Щ�С�һ����ֻ��һ��PRI
MARY   KEY�������û��PRIMARY   KEY����һ��Ӧ�ó���Ҫ���ڱ���ʹ��PRIMARY   K
EY����MySQL���ص�һ��UNIQUE���������û����ΪPRIMARY   KEY��NULL�С�

�� �� 
yangyangsss 
(yangyang) �Ĵ������ᵽ: ��: ������testʱ ����create table����������
:     PRIMARY KEY(trade_seq_num),
:     KEY (stock_code)
: �������keyֻ������ô  ����unique key.


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