Oracle 系统函数

个人笔记(!)

1.decode(var,var1,var1_1,var2,var2_2,.....,var_n) 函数

select decode(substr('abcd',1,1),'a','1','b','2','0') from dual; = >1

select decode(substr('abcd',3,1),'a','1','b','2','0') from dual; = >0

2.case when函数

update students set grade =

case

when score > 90 then 'A '

when score > 80 then 'B'

when score > 70 then 'C'

else 'D' end

3.instr 函数

select instr('abc','a') from dual; => 1

select instr('abc','d') from dual; => 0

4.lpad

5.rpad

6.ltrim,rtrim,trim