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 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 USERNAME                                  NOT NULL VARCHAR2(30)
 USER_ID                                   NOT NULL NUMBER
 PASSWORD                                           VARCHAR2(30)
 ACCOUNT_STATUS                            NOT NULL VARCHAR2(32)
 LOCK_DATE                                          DATE
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Virtual Columns in Oracle Database 11g

When queried, virtual columns appear to be normal table columns, but
their values are derived rather than being stored on disc. The syntax
for defining a virtual column is listed below.
column_name [datatype] [GENERATED ALWAYS] AS (expression) [VIRTUAL]
If the datatype is omitted, it is determin ......

OracleÖеÄcovering index

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±ÈÈçÓи´ºÏË÷ÒýΪ3¸ö×ֶΣºf1 + f2 + f3,ÇëÎÊ: 
1: select f1, f2, f3, f4 from table where f1 = 'XX' and f2 = 'XX'. ......

OracleË÷Òý±Ê¼Ç

 Ò».B-TreeË÷Òý(b-tree index)
1. Ñ¡ÏîÔñË÷Òý×ֶεÄÔ­Ôò: 
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ÔÚÑ¡ÔñÐԺܲîµÄ×Ö¶ÎÉϽ¨Ë÷ÒýÖ»ÓÐÔÚÕâ¸ö×Ö¶ÎµÄ ......

ÆÀ:Å·ÃË×èÄÓOracle¼æ²¢Sun

 ËäÈ»ÎÒÃÇÖªµÀÉ̵À¹îÒ²,ÕâƪÎÄÕ»¹ÊÇÄܹ»ÈÃÎÒÃÇ´ÓijЩ½Ç¶ÈÉϹ۲졣±ÈÈçÅ·ÃËÓµ»¤¿ª·Å¼¼Êõ,Å·ÃËÒªÆÀ¼ÛOracleÓµÓÐMySQLºÍJavaËùÔì³ÉµÄÓ°Ïì,everything is politicalÒÑÈ»ÊÇÒ»Ìõ´ó·¹æÔòÁË£¬ÎÒÃÇ»¹ÊÇÄܹ»Ðá³öÕâ¸ö»Ï×ÓÏÂÃæÂôµÃ»¹ÊÇÀûÒæ¹Ï·ÖµÄÀϾÀ¸ð£¬×ܲ»ÄÜɶºÃʶ¼ÈÃÄãÃÀ¹úÀÐÕ¼ÁË¡£µ«ÊÇÎÒÏëÒ²Ö»ÊǸöʱ¼äÎÊÌ⣬ҲÐí±³ºóÍÆÊÖÒ ......

Oracle ´¥·¢Æ÷,ÐòÁÐÓÃ;

 1¡¢´´½¨±ít1 £ºcreate table t1 (id number,name nvarchar(8))£»
2¡¢´´½¨ÐòÁÐ £ºCREATE SEQUENCE t1_id INCREMENT BY 1 START WITH 1 MAXVALUE
1.0E28 MINVALUE 1 NOCYCLE CACHE 20 NOORDER
3. ´´½¨´¥·¢Æ÷ £º
CREATE TRIGGER tig_insert_t1
BEFORE INSERT ON "YINZQ"."T1"
begin
if (:new.id is null) then ......
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