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DECODEÓÐʲôÓÃ;ÄØ£¿ Ïȹ¹ÔìÒ»¸öÀý×Ó£¬¼ÙÉèÎÒÃÇÏë¸øÖ°Ô±¼Ó¹¤×Ê£¬Æä±ê×¼ÊÇ£º¹¤×ÊÔÚ8000ÔªÒÔϵĽ«¼Ó20£¥£»¹¤×ÊÔÚ8000ÔªÒÔÉϵļÓ15£¥£¬8000ÔªµÄ²»±ä.Èç¹ûÏëÏÈÔ¤ÀÀһϼӹ¤×ʺóµÄ½á¹û¿ÉÒÔÓÃdecodeº¯Êý.ÈçÏÂ:
select decode(sign(salary - 8000),1,salary*1.15,-1,salary*1.2,salary) from employee
DECODEµÄÓï·¨£ºDECODE(value,if1,then1,if2,then2,if3,then3,...,else)£¬±íʾÈç¹ûvalueµÈÓÚif1ʱ£¬DECODEº¯ÊýµÄ½á¹û·µ»Øthen1,...,Èç¹û²»µÈÓÚÈκÎÒ»¸öifÖµ£¬Ôò·µ»Øelse¡£³õ¿´Ò»Ï£¬DECODE Ö»ÄÜ×öµÈÓÚ²âÊÔ£¬µ«¸Õ²ÅÒ²¿´µ½ÁË£¬ÎÒÃÇͨ¹ýһЩº¯Êý»ò¼ÆËãÌæ´úvalue£¬ÊÇ¿ÉÒÔʹDECODEº¯Êý¾ß±¸´óÓÚ¡¢Ð¡ÓÚ»òµÈÓÚ¹¦ÄÜ¡£
decode()º¯ÊýʹÓü¼ÇÉ
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1¡¢Windows NT4.0+ORACLE 8.0.4
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decode(Ìõ¼þ,Öµ1,·ÒëÖµ1,Öµ2,·ÒëÖµ2,...Öµn,·ÒëÖµn,ȱʡֵ)
¸Ãº¯ÊýµÄº¬ÒåÈçÏÂ:
IF Ìõ¼þ=Öµ1 THEN
RETURN(·ÒëÖµ1)
ELSIF Ìõ¼þ=Öµ2 THEN
RETURN(·ÒëÖµ2)
......
ELSIF Ìõ¼þ=Öµn THEN
RETURN(·ÒëÖµn)
ELSE
RETURN(ȱʡֵ)
END IF
· ʹÓ÷½·¨:
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select decode(sign(±äÁ¿1-±äÁ¿2),-1,±äÁ¿1,±äÁ¿2) from dual; --È¡½ÏСֵ
sign()º¯Êý¸ù¾Ýij¸öÖµÊÇ0¡¢ÕýÊý»¹ÊǸºÊý£¬·Ö±ð·µ»Ø0¡¢1¡¢-1
ÀýÈç:
±äÁ¿1=10£¬±äÁ¿2=20
Ôòsign(±äÁ¿1-±äÁ¿2)·µ»Ø-1£¬decode½âÂë½á¹ûΪ“±äÁ¿1”£¬´ïµ½ÁËÈ¡½ÏСֵµÄÄ¿µÄ¡£
2¡¢±í¡¢ÊÓͼ½á¹¹×ª»¯
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month char(6) --Ô·Ý
sell number(10,2) --ÔÂÏúÊÛ½ð¶î
ÏÖÓÐÊý¾ÝΪ:
200001 1000
200002 1100
200003 1200
200004 1300
&
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create table emp2 as select * from emp
create table emp3 as select * from emp
create table dept2 as select * from dept
create table salgrade2 as select * from salgrade
2.²é¿´±íµÄÉè¼ÆÇé¿ö:desc dept2;±íʾ²é¿´±ídept2µÄÉè¼ÆÇé¿ö.
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