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½ñÌ칫˾ÒòΪҵÎñÐèÒª,ÐÞÒªÐÞ¸Äij¸ö×Ö¶ÎÊý¾ÝÀàÐÍÓÐnumber(5),±äΪnumber(5,2)ÐÍ
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alter table tb_test modify permile number(5,2);
µ«ÊÇÓÐÊý¾ÝµÄ»° ¾Í²»ÄÜÓÃÉÏÃæ·½·¨ÁË,
alter table tb_test add permile_temp number(5,2)
update tb_test set permile_temp=permile;
alter table drop column permile;
alter table test rename column permile_temp to permile;
ÕâÖÖ·½·¨»áʹÁÐÃû·¢Éú±ä»¯,¶øÇÒ×Ö¶Î˳ÐòÔö¼Ó ÓпÉÄÜ·¢ÉúÐÐÇ¨ÒÆ,¶ÔÓ¦ÓóÌÐò»á²úÉúÓ°Ïì
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ÒÔÏÂÊǽű¾:
-- Ìí¼ÓÒ»¸öÁÙʱÁÐpermile_temp ÀàÐÍΪ number
alter table tb_test add permile_temp number;
-- ÉèÖÃÒª¸Ä¶¯µÄÁÐpermile ¿ÉÒÔΪNULL
alter table tb_test modify permile null;
-- °Ñpermile ÁеÄֵȫ²¿¸üиøÁÙʱÁÐpermile_temp£¬È»ºó°Ñ permile ¸üÐÂΪNULL
update tb_test set permile_temp=permile,permile=null;
commit;
-- °ÑÁÐÄ¿±êÁÐ permile Êý¾ÝÀàÐ͸Ķ¯Îªnumber(5,2)
alter table tb_test modify permile number(5,2);
-- °Ñpermile ÁеÄֵȫ²¿¸üлØÀ´£¬È»ºó°Ñ ÁÙʱÁÐ ¸üÐÂΪNULL
update tb_test set permile=permile_temp,permile_temp=null;
commit;
-- ×îºóɾ³ýÌí¼ÓµÄÁÙʱÁÐ
alter table tb_test drop column permile_temp;
-- ×îºó»¹ÔÁÐ permile ²»ÔÊÐíΪNULL
alter table tb_test modify permile not null;
select * from tb_test ;
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