oracle資料庫（三）高階查詢

-- 根據員工的上級編號進行層級關聯 select level ,empno,ename,mgr from emp connect by prior empno = mgr start with mgr is null order bylevel

;

translate(expr,from_string,to_string)替換知道的字元，to_string為null時返回null，沒有匹配時的字元直接刪除

regexp_replace(src,re,new)正則替換字元

regexp_substr(src,re,n)字串分列，re.split()

-- 正則替換
select regexp_replace(
'adsfaad'
,'[^a]'
,'0'
)from dual;
-- 字串分列
select 
regexp_substr(
'192.168.0'
,'[^.]+',1
,1) a1
,regexp_substr(
'192.168.0'
,'[^.]+',1
,2) a2
,regexp_substr(
'192.168.0'
,'[^.]+',1
,3) a3
from dual;
-- 計算字元出現數量
select regexp_count(
'adsfaad'
,'a'
)from dual;
select length(regexp_replace(
'adsfaad'
,'[^a]'))
from dual;
select translate(
'adsfaad'
,'a'
||'adsfaad'
,'a'
)from dual;
-- 刪除不需要字元
select
replace
(translate(job,
'man'
,'aaa'),
'aaa',''
)from emp;
select regexp_replace(job,
'[man]',''
)from emp;
-- 字元數字分離
select 
regexp_replace(
'sdfsf04'
,'[0-9]',''
) 字元
,regexp_replace(
'sdfsf04'
,'[^0-9]',''
) 數字
from dual;
select 
translate(
'sdfsf04'
,'a0123456789'
,'a'
) 字元
,translate(
'sdfsf04'
,'0123456789'
||'sdfsf04'
,'0123456789'
) 字元
from dual;

-- 帶單引號字元
select
'adsf'
'asfads'
from dual;
select q'' from dual;

-- 用法
select 
e.deptno
,listagg(e.ename,
',')
within
group
(order
by e.empno) names
from emp e
group
by e.deptno;
-- 展示累計的邏輯
select 
e.*,
sum(sal)
over
(partition
by e.deptno order
by hiredate),(
select listagg(sal,
'+')
within
group
(order
by e2.hiredate)
from emp e2
where e2.deptno =
30and e2.hiredate <= e.hiredate
)-- e.hiredate的資料迭代進入計算，迭代出
from emp e
where e.deptno =
30;

-- 開窗 rows --物理開窗 range --邏輯開窗 unbounded preceding --前面所有行 current row--當前行 unbounded following --後面所有行 range between unbounded preceding andcurrent row-- 預設視窗 -- 顯示員工資訊按各部門薪資降序排列 select empno ,ename ,sal ,dense_rank( )over (partition by deptno order by sal desc ) sal_rank

from emp;

-- 顯示各部門最高工資的員工資訊
select 
deptno
,min(sal) keep (dense_rank first
order
by sal desc
) top_sal
from
empgroup
by deptno;

select
level
from emp connect
bylevel
<=1;
select
level
from dual connect
bylevel
<=
4;

select user_ind_columns.index_name 索引名稱, user_ind_columns.table_name 表名, user_ind_columns.column_name 欄位名, user_indexes.uniqueness 約束 from user_ind_columns, user_indexes where

user_ind_columns.index_name = user_indexes.index_name;

select table_name from user_tables;

一行拆分多行顯示

with t as
(select
'x,y,z'
as lll from  dual
union
allselect
'***,y,zz,aaaaa,b,ccc,d,e,f,ggg'
as lll from dual
)select lll,  
regexp_substr(lll,
'[^,]+',1
,level)as
value
from t  
connect
by  lll = prior lll  
and instr(lll||
',',
',',1,
level
)>
0and prior dbms_random.
value
isnot
null
;

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