[討論] three-schema architecture ?

[kikilalagirl (kikilala)]

Three-schema architecture 分為
1. External schema
2. Conceptual schema
3. Internal schema

請問甚麼樣的語法 , 才能各自代表每一層呢 ?

CREATE TABLESPACE 代表 Internal schema ?

CREATE TABLE 代表 Conceptual schema ?

什麼樣的語法代表 External schema 呢 ?

-----

CREATE TABLESPACE "IMAGEDATA"
NOLOGGING
DATAFILE
'D:"oracle"oradata"DATA01.dbf' SIZE 2000M,
'D:"oracle"oradata"DATA02.dbf' SIZE 2000M,
'D:"oracle"oradata"DATA03.dbf' SIZE 2000M,
'D:"oracle"oradata"DATA04.dbf' SIZE 2000M,
'D:"oracle"oradata"DATA05.dbf' SIZE 2000M
EXTENT MANAGEMENT LOCAL SEGMENT SPACE MANAGEMENT AUTO

-----

CREATE TABLE Customer
( First_Name char(50),
  Last_Name char(50),
  Address char(50),
  City char(50),
  Country char(25),
  Birth_Date datetime
);

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