?
使用Oracle特有的查詢語法, 可以達到事半功倍的效果1. 樹查詢
create
?
table
?tree?(
????id?
number
(
10
)?
not
?
null
?
primary
?
key
,
????name?
varchar2
(
100
)?
not
?
null
,
????super?
number
(
10
)?
not
?
null
????????????????
//
?
0
?
is
?root
);
--
?從子到父
select
?
*
?
from
?tree?start?
with
?id?
=
???connect?
by
?id?
=
?prior?super?
--
?從父到子
select
?
*
?
from
?tree?start?
with
?id?
=
???connect?
by
?prior?id?
=
?suepr
--
?整棵樹
select
?
*
?
from
?tree?start?
with
?super?
=
?
0
?connect?
by
?prior?id?
=
?suepr
2. 分頁查詢
select
?
*
?
from
?(?
????
select
?my_table.
*
,?rownum??my_rownum?
from
?(?
????????
select
?name,?birthday?
from
?employee?
order
?
by
?birthday
????)?my_table?
where
?rownum?
<
?
120
?
)?
where
?my_rownum?
>=
?
100
;
3.?累加查詢, 以scott.emp為例
select
?empno,?ename,?sal,?
sum
(sal)?
over
(
order
?
by
?empno)?result?
from
?emp;
?
?????EMPNO?ENAME?????????????SAL?????RESULT
--
--------?----------?----------?----------
??????
7369
?SMITH?????????????
800
????????
800
??????
7499
?ALLEN????????????
1600
???????
2400
??????
7521
?WARD?????????????
1250
???????
3650
??????
7566
?JONES????????????
2975
???????
6625
??????
7654
?MARTIN???????????
1250
???????
7875
??????
7698
?BLAKE????????????
2850
??????
10725
??????
7782
?CLARK????????????
2450
??????
13175
??????
7788
?SCOTT????????????
3000
??????
16175
??????
7839
?KING?????????????
5000
??????
21175
??????
7844
?TURNER???????????
1500
??????
22675
??????
7876
?ADAMS????????????
1100
??????
23775
??????
7900
?JAMES?????????????
950
??????
24725
??????
7902
?FORD?????????????
3000
??????
27725
??????
7934
?MILLER???????????
1300
??????
29025
4. 高級group by
select
?decode(
grouping
(deptno),
1
,
'
all?deptno
'
,deptno)?deptno,
???????decode(
grouping
(job),
1
,
'
all?job
'
,job)?job,
???????
sum
(sal)?sal
from
?emp?
group
?
by
?ROLLUP(deptno,job);
DEPTNO???????????????????????????????????JOB??????????????SAL
--
--------------------------------------?---------?----------
10
???????????????????????????????????????CLERK???????????
1300
10
???????????????????????????????????????MANAGER?????????
2450
10
???????????????????????????????????????PRESIDENT???????
5000
10
???????????????????????????????????????
all
?job?????????
8750
20
???????????????????????????????????????CLERK???????????
1900
20
???????????????????????????????????????ANALYST?????????
6000
20
???????????????????????????????????????MANAGER?????????
2975
20
???????????????????????????????????????
all
?job????????
10875
30
???????????????????????????????????????CLERK????????????
950
30
???????????????????????????????????????MANAGER?????????
2850
30
???????????????????????????????????????SALESMAN????????
5600
30
???????????????????????????????????????
all
?job?????????
9400
all
?deptno???????????????????????????????
all
?job????????
29025
5. use hint
當多表連接很慢時,用ORDERED提示試試,也許會快很多
SELECT
?
/*
+?ORDERED?
*/
*
?
??
FROM
?a,?b,?c,?d?
?
WHERE
?
?
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