Bài giảng Truy vấn nâng cao

TRUY VẤN NÂNG CAO


Bảng tạm
with tscv as (
select manv, count(*) ts from phancong
group by manv
)
select manv, tennv,
(select ts from tscv where manv=nv.manv)
/ (select sum(ts) from tscv) AS xxx
from nhanvien nv
-------------------------------------------------select manv, count(*)/(select sum(ts) from tscv)


Truy vấn đệ quy
create table quanhe_nhanvien (manv char(5)
primary key,tennv char(20), manvct char(5))
-------------------------------

manv

tennv

manvct

Nv001

A

null

Nv002

B

null

Nv003

C

Nv001

Nv004

D

Nv001

Nv005

E

Nv003


Truy vấn đệ quy
with truy
(manv,tennv,manvct,mucdo,cay,cayten)
as (

select a.manv,a.tennv,a.manvct,1 as
mucdo,
cast('' as varchar(max)) as
cay,
cast('' as varchar(max)) as
cayten
from quanhe_nhanvien a


Truy vấn đệ quy
with truy (manv,tennv,manvct,kq) as (
select

a.manv,a.tennv,a.manvct,

cast('' as varchar(max)) as kq
from quanhe_nhanvien a
where a.manvct is null
union all
select

b.manv,b.tennv,b.manvct,

(truy.kq + '\' + b.manvct) as kq
from quanhe_nhanvien b inner join truy
on truy.manv = b.manvct


Truy vấn đệ quy
(kết quả)

Manv

Tennv

Manvct

Mucdo

cay

cayten

Nv001

A

null

1

Nv002

B

Null

1

Nv003

C

Nv001

2

\Nv001

\A

Nv004

D

Nv001

2

\Nv001

\A

Nv005

E

Nv003

3

\Nv001\Nv003

\A\C

Nv006

F

Nv005

4

\Nv001\Nv003\Nv005

\A\C\E


Truy vấn đệ quy
with truy
(manv,tennv,manvct,mucdo,cay,cayten)
as (
select a.manv,a.tennv,a.manvct,1 as
mucdo,
cast('' as varchar(max)) as
cay,
cast('' as varchar(max)) as
cayten
from quanhe_nhanvien a

Truy vấn chéo 
(Pivot)
create table baocaods
(nam int, mahang char(5), sl int, daily char(5),
constraint kc_baocaods primary key (nam,mahang,daily))
--------------------------------------------------------(1998,'G1',3,'D1')
(1999,'G1',4,'D1')
(1997,'G1',2,'D1')
(1998,'G2',9,'D1')
(1999,'G2',4,'D1')
(1997,'G2',6,'D1')
(1998,'G1',32,'D2')


Truy vấn chéo
(Pivot)
select mahang,[1997],[1998],[1999]
from (select mahang,sl,nam from baocaods) as a
pivot (sum(sl) for nam in [1997],[1998],[1999])) as b
------------------------------------------------------

[1997],[1998],[1999] : là các giá trị
mahang,sl,nam : gồm đúng 3 cột gồm Header Row,Header column, 
Value.
Mệnh đề From và Pivot phải đặt lại tên mới.

------------------------------------------------------


Truy vấn 

(Cross – outer apply)
select *
From nhanvien as nv cross apply
( select count(*) as ts from phancong as pc
where pc.manv = nv.manv
) as tongsoviec
Làm lại truy vấn count cho từng manv 
(có thể thay câu count thành hàm tính tốn cho ra Table)
Select *
from nhanvien as nv inner join
(select manv,count(*) ts from phancong