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Oracle???????

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?????Microsoft Windows XP [?? 5.1.2600]

????Oracle9i Enterprise Edition Release 9.2.0.1 - ????

?????SunOS 5.9 [Solaris 9]

????Oracle10g Enterprise Edition Release 10.1.0.3 - ????

???????

?????

char - VARCHAR2

number

null - ????

escape character - ????

order by / group by

dual - ???

?????

a. char - VARCHAR2(1) b. number

SQL????

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CREATE TABLE test (x char, y VARCHAR2(10)) tablespace users;

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DESCRIBE test;

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- x: CHAR(1) - ?????????????? - ????
- y: VARCHAR2(10) - ?????????????? - ????

?????

ALTER TABLE test MODIFY (x CHAR(10));

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INSERT INTO test VALUES('a', 'b');

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SELECT * FROM test WHERE x = 'a';

?????

x | y  
a | b

SELECT * FROM test WHERE y = 'b';

?????

x | y  
a | b

SELECT * FROM test WHERE y > 'b';

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x | y  
a | b

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