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create sequence type_id increment by 1 start with 1;
Õâ¾äÖУ¬type_idΪÐòÁкŵÄÃû³Æ£¬Ã¿´ÎÔö³¤Îª1£¬ÆðʼÐòºÅΪ1¡£
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ÐòÁпÉÒÔ±£Ö¤¶à¸öÓû§¶ÔͬһÕÅ±í½øÐвÙ×÷ʱÉú³ÉΨһµÄÕûÊý,ÀûÓÃÐòÁпÉÒÔ×Ô¶¯Éú³ÉÖ÷¹Ø¼ü×Ö,ÐòÁÐÖ»´æÔÚÓÚÊý¾Ý×ÖµäÖÐ.
CREATE SEQUENCE sequence
[INCREMENT BY n]
[START WITH n]
[{MAXVALUE n|NOMAXVALUE}]
[{MINVALUE n|NOMINVALUE}]
[{CYCLE |NOCYCLE}]
[{CACHE n|NOCACHE}];
INCREMENT BY--Ö¸¶¨²½³¤
START WITH--Ö¸¶¨³õʼֵ
MAXVALUE--¶¨ÒåÐòÁÐÉú³ÉµÄ×î´ó±àºÅ.ĬÈϵÄMAXVALUE¾ÍÊÇNOMAXVALUE,¶ÔÓÚµÝÔöÐòÁÐΪ10^27,¶ÔÓڵݼõÐòÁÐΪ-1
MINVALUE--¶¨ÒåÐòÁеÄ×îС±àºÅ,ĬÈϵÄMINVALUEΪNOMINVALUE,¶ÔÓÚµÝÔöÐòÁÐΪ1,µÝ¼õÐòÁÐΪ-10^26.
CYCLE--ÅäÖÃÐòÁÐÔÚ´ïµ½½çÏÞÖµÊ±ÖØ¸´±àºÅ
NOCYCLE--´ïµ½½çÏÞֵʱ²»Öظ´±àºÅ,ÕâÊÇĬÈÏÖµ,µ±ÄãÊÔͼÉú³ÉMAXVALUE+1ʱ½«·µ»ØÒì³£.
CACHE--¶¨ÒåÔÚÄÚ´æÖб£ÁôµÄÐòÁбàºÅ¿éµÄ´óС,ĬÈÏֵΪ20.
NOCACHE--Ç¿ÖÆÊý¾Ý´Êµä¶ÔÓÚÉú³ÉµÄÿ¸öÐòÁбàºÅ½øÐиüÐÂ,±£Ö¤ÔÚÉú³ÉµÄ±àºÅÖÐûÓпÕȱ,µ«ÕâÑù»á½µµÍÐÔÄÜ.
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CREATE SEQUENCE dept_deptid_seq
INCREAMENT BY 10
START WITH 120
MAXVALUE 9999
NOCACHE
NOCYCLE;
//Èç¹ûÊÇÓÃÀ´Éú³ÉÖ÷¼üÖµµÄ»°,²»ÒªÓÃCYCLEÑ¡Ïî,¶øÇÒÃüÃûÐòÁÐʱ×îºÃÄÜÌåÏÖËüµÄDZÔÚÓÃ;ÒÔ±ãÓÚÀí½â.
È·ÈÏÐòÁÐ
SELECT sequence_name,min_value,max_value,increament_by,last_number
from user_sequences;
//Èç¹ûÄãÖ¸¶¨ÁËNOCACHEÑ¡Ïî,ÄÇôLAST_NUMBERÁн«ÏÔʾÏÂÒ»¿ÉÓõÄÐòÁкÅ.
ʹÓÃNEXTVAL¿ÉÒÔ·ÃÎÊÐòÁÐÖеÄÏÂÒ»¸ö±àºÅ,µ«ÎÊÌâ³£³£³öÏÖÔڻỰ³õʼÐòÁÐ֮ǰ²éѯÆäµ±Ç°ÐòÁкÅCURRVAL
CREATE SEQUENCE emp_seq
NOMAXVALUE
NOCYCLE;
È»ºó²éѯ
SELECT emp_seq.currval
from dual;
½«·µ»Ø´íÎó,ÎÊÌâ¾ÍÔÚÓÚÄãÊÓͼÒýÓÃCURRVAL֮ǰ,ÔÚÄãµÄ»á»°Öв¢Ã»ÓÐʹÓÃNEXTVALÏȳõʼ»¯´ËÐòÁÐ.
SELECT emp_seq.nextval
from dual;
ÕâÑùÔÙ²éѯCURRVAL¾Í²»»á³ö´íÁË.
ʹÓÃÐòÁÐ
INSERT INTO departments(department_id,department_name,location_id)
VALUES (dept_deptid_seq.NEXTVAL,'Support',2500);
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SQL> select ascii(A) A,ascii(a) a,ascii(0) zero,ascii( ) space from dual;
A A ZERO SPACE
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65 97 48 32
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SQL> select chr(54740) zhao,chr(65) chr65 from dual;
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1. ASCII: ·µ»ØÓëÖ¸¶¨µÄ×Ö·û¶ÔÓ¦µÄÊ®½øÖÆÊý;
SQL> select ascii('A') A,ascii('a') a,ascii(0) zero,ascii('') space from dual; 
   A A ZERO SPACE
   --------- --------- --------- ---------
   65 97 48 
2. CHR:¸ø³öÕûÊý,·µ»Ø¶ÔÓ¦µÄ×Ö·û;
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Oracleϵͳ¹ÜÀíºÍϵͳ×ÊÁÏ»ñÈ¡µÄһЩ»ù±¾ÃüÁî

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SELECT name,created,log_mode,open_mode from v$database;
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