--update 这个字段的所值为2
update tab a set a.字段1=2;
--带条件的update
update tab a set a.字段1=2 where id=10000;
--根据一个表update 另外一个表
update tab a set a.字段=(select b.字段 from tab1 b where a.id=b.fid)
where exists (select 1 from tab1 b where a.id=b.fid)
--update 多个字段
update tab a set (a.字段,a.字段1)=(select b.字段,b.字段1 from tab1 b where a.id=b.fid)
where exists (select 1 from tab1 b where a.id=b.fid)
update tab a set a.字段=(select b.字段 from tab1 b where a.id=b.fid) where a.字段1=\'地名\'
在oracle的update语句语法中，除了可以update表之外，也可以是视图，所以有以下1个特例：
update (select a.city_name,b.city_name as new_name
from customers a,
tmp_cust_city b
where b.customer_id=a.customer_id
)
set city_name=new_name
这样能避免对B表或其索引的2次扫描，但前提是 A(customer_id) b(customer_id)必需是unique index或primary key。否则报错：
update 和 decode 结合使用
update tpr_fwzh set jjbz=decode(jjbz,1,2,2,4,3,1,4,6,5,3,6,10,7,7,8,8,10,9,jjbz)
update 与case when 结合使用
--修改对应关系
UPDATE TEMP_ZS_PXJH_MXFW SET XZQ= --行政区
CASE XZQ
WHEN \'0,27,28,29,30,31,32,33,34,35,59\' THEN
\'320202,320203,320204,320205,320206,320211,320291,320281,320282,320215\'
WHEN \'0,27,28,29,30,31,32,33,34,59\' THEN
\'320202,320203,320204,320205,320206,320211,320291,320281,320215\'
WHEN \'0,27,28,29,30,31,32,33,34,59,35\' THEN
\'320202,320203,320204,320205,320206,320211,320291,320281,320282,320215\'
WHEN \'0,27,28,29,30,31,32,33,59\' THEN \'320202,320203,320204,320205,320206,320211,320291,320215\'
WHEN \'34\' THEN \'320281\'
WHEN \'0,35\' THEN \'320282\'
WHEN \'0,34\' THEN \'320281\'
WHEN \'0\' THEN NULL
ELSE XZQ END,
ZZDJ= --资质等级
CASE ZZDJ
WHEN \'0,2,3,46,47,70\' THEN \'2,3,1,4,5\'
WHEN \'0,2,3,46,47\' THEN \'2,3,1,4\'
WHEN \'0\' THEN NULL
ELSE ZZDJ END,
HYLX= --会员类型
CASE HYLX
WHEN \'0,4,5,48,64,71\' THEN \'1,2,3,4,5\'
WHEN \'0,4,5,48\' THEN \'1,2,3\'
WHEN \'0,4,5,48,64\' THEN \'1,2,3,4\'
WHEN \'0\' THEN NULL
ELSE HYLX END