Oracle查詢筆記

-- tanslate(str,from_str,to_str)
-- 將str中的from_str替換成to_str
select translate('hello','e','o') t
from dual;-- instr(str,des_str)
-- 可以實現like功能
select instr('hello','g'),instr('hello','h'),instr('hello','l')
from dual; -- decode(value,s1,r1,s2,r2,default)
-- 類似于if else
select decode('1','1','一級部門','2','二級部門','其他部門') as dept
from dual;-- case表達式
select case 1when 1 then '001'when 2 then '002'else '003'end as le
from dual;-- 層次化查詢(樹形結構)
select level,id,pid,name
from t_test 
start with pid is null
connect by prior id=pid;

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