select *,(case when SEX is "男" then 0 when SEX is "女" then 1 else 2 end) as sex from user;
等價於 select decode(SEX,"男",0,"女",1,2)sex from user;若查詢的某個字段爲null 但是顯示時 想顯示 其他值(以顯示0爲例),則可以
select *,nvl(fenshu,0) from score;
等價於 select *,(if(fenshu is null) then 0 else fenshu end if) fs from score;
若 性別只要2種情況 select *,(if(SEX.equals("男")) then 0 else 1 end if) sex from user;
coalesce(n1,n2) 若n1!=null 則 返回n1 否則 判斷 n2是否爲空 若不爲空則返回 n2 若都爲空 則 返回null
(coalesce (N1, N2, ...,Nn)依次參考各參數表達式,遇到非null值即停止並返回該值)