: , () , , . . :
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R-W 2 , 1;
W-R 2 , 1.
. - . ( , ) ( ). , . . , .
( , -) , . , T r T r ( ):
S (Shared), ( );
X (eXclusive), , ( ).
(deadlocks) . .
T1 T2: T 1 T2 r1 r2, ; T1 r2, T2 - r1. , , , - . , , . -, .. , , . ; . , , , .. - , . , , . , , .
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, , . ( ) : T1 T2, , T1 T2. T t, T. r T ( ). r T1 :
1. , T, .
2. T , T1 r .
3. T , T1 .
4. , r , T1 .
5. T1 T , t(T) > t(T1) (.. T "", T1), T, T1 .
6. t(T) < t(T1) (T "" T1), T1 .
, . , . , . , , .
6.1. Microsoft Borland.
6.2. .
6.3. .
6.4. - -.
6.5. -.
6.6. () .
6.7. .
6.8. .
6.9. .
6.10. .
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6.11. .
6.12. : READ UNCOMMITTED ( ), REPEATABLE READ ( ), SERIALIZABLE ( ), READ COMMITTED ( ).
6.13. : READ UNCOMMITTED ( ), REPEATABLE READ ( ), SERIALIZABLE ( ), READ COMMITTED ( ).
7. ACCESS
. Microsoft Access. Access MS Office , . , . Access , . . :
1. . ;
2. . , ;
3. , , , , ..;
4. . , . ;
5. MS Office.
ACCESS
Access , . , . Access MS Office .
Access :
1. . ;
2. . , ;
3. , , , , ..;
4. . , . ;
5. MS Office.
Access , . , . . . , . . . . , . Access Access. Access Developer Toolkit , Access DLL. , ( ) .
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, Access, . Access , . Access , , , , . Access , Web , , MS SQL Server. .
. , . . , , . . Access , , .
. , . , . : QBE (Query By Example - ) SQL. , , . , .. Access . , .
. , . , , . . , , , . , . , , , , , , . .
, Access. , Visual Basic for Application (VBA). VBA . , , .
. , . Access , (, ) .
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. , , , , . . Access , Word Excel.
. , , Access .
Access . , . , , , , .. , , . Access . .
. , VBA, . Access , , , , , . . , , , .
Access . 7.1. , . , . , . Access, , VBA.
, , VBA. ; , ; , . VBA , Access, ..
. 7.1. Microsoft Access
Access (. 7.2), .
.7.2
, . , . , . , 64 ( ), , , .
Access 9 :
Text | 255 (255 ) | ||
Memo | 64 (65535 ) | ||
Number | (1, 2, 4, 8 12 ) | ||
/ | Date/Time | / (8 ) | |
Currency | ( ), , 15 4 (8 ) | ||
AutoNumber | , . . (4 ) | ||
Yes/No | (1 ) | ||
OLE | OLE Object | OLE. 1 ( ) | |
Hyperlink | , . : , ; ( UNC URL) . 2048 . |
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, 255 . / / . / , , . ( ) ( ). , . -. OLE , , , , Object Linking and Embedding (OLE). OLE . . , Access Microsoft Word, Microsoft Excel, Microsoft PowerPoint Paint, WAV .. OLE , , , , . , , , .
, . , , , 0 ( ). , , .
. . , Access . . :
. , . 1 255 (); 50 . :
Byte | 0 255. 1 . | |
Integer | -32768 +32767. 2 . | |
Long Integer | -2147483648 +2147483647. 4 . | |
Single | 7 . -3,402823E38 1,401298E45 , 1,401298E45 3,402823E38 . 4 . | |
Double | 15 . -1,79769313486231E308 -4,94065645841247E324 4,94065645841247E324 1,79769313486231E308 . 8 . | |
Real | 28 . 10^281 10^281. 12 . |
. . . , , . :
General | ( .) , . | |
Currency | . | |
Fixed | . . | |
Standard | , . | |
Percent | 100 %. | |
Exponential | . |
/ . , , , . . . :
: () | . ( Microsoft Windows). |
/ | . ( Microsoft Windows). |
c | . |
d | , (1-31). |
dd | , (01-31). |
ddd | (-). |
dddd | (-). |
ddddd | . |
dddddd | . |
w | (1-7). |
ww | (1-53). |
m | , (1-12). |
mm | , (01-12). |
mmm | (-). |
mmmm | (-). |
q | (1-4). |
y | (1-366). |
yy | (01-99). |
yyyy | (0100-9999). |
h | , (0-23). |
hh | , (00-23). |
n | , (0-59). |
nn | , (00-59). |
s | , (0-59). |
:
/ | Yes/No |
/ | True/False |
/ | On/Off |
Access , . , Access, ( , , , Null), , . :
, , . , Access 0. | |
# | , , . , Access . |
- + $ () | . |
, . | |
\ | , \ ( , ). |
! | . , . |
* | , * . |
% | 100 . |
- | . |
+ + | : + . |
[] | , . : (Black), (Blue), (Green), (Cyan), (Red), (Magenta), (Yellow), (White). |
, , , , , , , 0, Null :
#, ##0.00; (#, ##0.00) []; ;
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@ | . |
& | . , . |
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. , , / , . , , , . , . , , Access _/_/_ , __ _______.
, . , , ; , . , 0, , 1. -. _. , , (" "). :
(0-9, ; (+) (-) ). | |
( ; (+) (-) ). | |
# | ( ; , ; (+) (-) ). |
L | ( , ). |
? | ( , ). |
A | ( ). |
A | ( ). |
& | ( ). |
C | ( ). |
.,:; - / | , , . ( , Microsoft Windows .) |
< | . |
> | . |
! | , . . . |
\ | , (, \A A). |
, : 8- (####) ##0\-####,
: LL 0000000.
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. , , OLE. , , , 0 1, , , . , , .
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IN :
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Null ? : , , . , Null. . , : . , . .
, , , , .
. , , , / , . . , , , , . , . M, OLE .
( ) , (. 7.3). ( ) , , .
. 7.3.
. , M . 16 , , M , Microsoft Access 97 , . , , 0, . 0, , , .
, , , , , . , , ; , ; , .
Access . . , Ctrl, . , . Primary Key. , , .. ( ).
. , (Relationships), ( ) . , , . . . Del.
. . 1 ∞. ∞ 1.