update语句问题

Question

update fljh set LEFT(ltrim(fld_wl_bh),2) = upper(LEFT(ltrim(fld_wl_bh),2))
请帮忙看下此语句有何问题？

Answer 1

只能这样写，不可以直接搞update fljh 
set fld_wl_bh=REPLACE(fld_wl_bh,LEFT(ltrim(fld_wl_bh),2),upper(LEFT(ltrim(fld_wl_bh),2)))

Answer 2

糾正如下：
update fljh set fld_wl_bh = ltrim(fld_wl_bh)
update fljh set fld_wl_bh = stuff(fld_wl_bh,1,2,upper(LEFT(fld_wl_bh,2)))

Answer 3

update fljh 
 set fld_wl_bh=upper(LEFT(ltrim(fld_wl_bh),2))
 where LEFT(ltrim(fld_wl_bh),2)=upper(LEFT(ltrim(fld_wl_bh),2))

Answer 4

update fljh SET fld_wl_bh=upper(LEFT(ltrim(fld_wl_bh),2))+LTRIM(RIGHT(fld_wl_bh,LEN(fld_wl_bh)-2))

Answer 5

update fljh set LEFT(ltrim(fld_wl_bh),2) = upper(LEFT(ltrim(fld_wl_bh),2))set 后面的LEFT(ltrim(fld_wl_bh),2) 只是函数转化后的虚拟列，也就说是返回值，并不是真实存在的列。