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²Ö¿âÃû³Æ ÉÌÆ·Ãû³Æ ÊýÁ¿
A
S001 12
A S002 17
A
S003 10
B S001 21
B
S002 5
B S003 0
C S001 100
C S002 11
C S003 25
(±íÒ»)
ÉÌ
Æ·Ãû³Æ ×Ü¿â´æ A B C
S001 133 12 21 100
S002 33 17 5 11
S003 35 10 0
25
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create
table
tb(²Ö¿âÃû³Æ
varchar
(
10
),ÉÌÆ·Ãû³Æ
varchar
(
10
),ÊýÁ¿
int
)
insert
into
tb
values
(
'
A
'
,
'
S001
'
,
12
)
insert
into
tb
values
(
'
A
'
,
'
S002
'
,
17
)
insert
into
tb
values
(
'
A
'
,
'
S003
'
,
10
)
insert
into
tb
values
(
'
B
'
,
'
S001
'
,
21
)
insert
into
tb
values
(
'
B
'
,
'
S002
'
,
5
)
insert
into
tb
values
(
'
B
'
,
'
S003
'
,
0
)
insert
into
tb
values
(
'
C
'
,
'
S001
'
,
100
)
insert
into
tb
values
(
'
C
'
,
'
S002
'
,
11
)
insert
into
tb
values
(
'
C
'
,
'
S003
'
,
25
)
go
--
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select
ÉÌÆ·Ãû³Æ,
sum
(ÊýÁ¿) ×Ü¿â´æ,
sum
(
case
²Ö¿âÃû³Æ
when
'
A
'
then
ÊýÁ¿
else
0
end
)
[
A
]
,
sum
(
case
²Ö¿âÃû³Æ
when
'
B
'
then
ÊýÁ¿
else
0
end
)
[
B
]
,
sum
(
case
²Ö¿âÃû³Æ
when
'
C
'
then
ÊýÁ¿
else
0
end
)
[
C
]
from
tb
group
by
ÉÌÆ·Ãû³Æ
/*
ÉÌÆ·Ãû³Æ ×Ü¿â´æ A B C
---------- ----------- ----------- ----------- -----------
S001 133 12 21 100
S002 33
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8.00.194 Microsoft SQL Server 2000
8.00.384 Microsoft SQL Server 2000 SP1
8.00.532 Microsoft SQL Server 2000 SP2
8.00.760 &nb ......
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constraint PK_USER prim ......
1. Q. What is a join?
A. Join is a process of retrieve pieces of data from different sets (tables) and returns them to the user or program as one joined collection of data.
2. Q. Can a table have more than one foreign key defined?
A. A table can have any number of foreig ......