
Karpova_bazy_dannyh
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42 |
3. |
- |
3 (),
-
4 (
).
. 3.6
.
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3 |
4 |
5 |
6 |
7 |
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. 3.6. |
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,
,
.
,
.
;
(
);
(
).
SCHEMA IS <>.
AREA NAME IS <>. RECORD NAME IS <
(
)>.
,
:
LOCATION MODE IS {DIRECT () |
L
<
USING <[
.]>

43
DUPLICATE ARE [NOT] ALLOWED
VIA <> SET (
) SYSTEM (
)}
-
:
WITHIN <> ARE/
<> <
> <
> <
>
-
.
.
,
.
,
.
,
,
<> <
>.<
> <
1-
.>
,
:
<> <
>.OCCURS <N> TIMES
N
.
-
:
SET NAME IS <>:
OWNER IS (<> |SYSTEM).
:
ORDER PERMANENT INSERTION IS {SORTED | NEXT | PREV | LAST | FIRST}
.
MEMBER IS <> {AUTOMATIC | MANUAL) {MANDATORY | OPTIONAL} KEY IS (ACCENDING | DESCENDING) <
>
-
.
-
,
CONNECT
-
.
MANDATORY, |
, |
- |
, |
. |
- |
. |
|
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|
- |
.


45
-
-
-
-
. 3.7. |
« |
» |
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- |
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. |
VIRTUAL |
|
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- |
.
RECORD
02 TYPE REAL
02 VIRTUAL
SOURCE IS .
OF OWNER OF -
SET
(FIND),
,
.
:
1. (
CALC USING
):
FIND <> RECORD BY CALC KEY <
>
2.:
FIND DUPLICATE <> RECORD BY CALC KEY
3.:
FIND OWNER OF CURRENT <> SET
4.:
FIND (FIRST | NEXT) <> RECORD IN CURRENT <
> SET


4
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(1841-1902). |
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(1839-1914) |
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1970 |
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( |
relation |
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N- |
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R |
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D1 D2 ... |
Dn |
D1 , D2 ,..., Dn (n 1), |
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D1 , D2 ,..., Dn |
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48 |
4. |
R D1
D2
...
Dn ,
D1
D2
...
Dn
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D3 |
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D1 ={ |
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D2= { |
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D3 ={3, 4, 5}. |
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18 |
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n
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R
4
3
5
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4
:

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49 |
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4. |
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R1,
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R1
5
5
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3
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o6
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,
-
,
-
,
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R
,
:
S R ( A1 , A2 , An ), A1
D1 .
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,
={=, <>,>=,<=,<,>}.
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-
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,
-
.
,
-
,
,
,
-
.

50 |
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4. |
S R1 |
( A1 , A2 ,..., An ), |
R1. |
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||
S R 2 |
(B1 , B2 ,..., Bn ), |
R2 |
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S R1 |
S R 2 |
1, n |
m, |
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2, Aj |
, B j D j. |
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(PRIMARY KEY), |
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- |
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- |
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- |
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(FOREIGN KEY).
. 4.1.
PRIMARY KEY FOREIGN KEY
«
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-
. |
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: |
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. 4.1). |
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