, . , , . , .
.
(, , _), , , . N " " " " , K " " " " " ". :
----------------------------------------------------
| | | _ |
----------------------------------------------------
| N | | |
| N | | |
| N | | |
| N | | |
| K | | |
| K | | |
----------------------------------------------------
:
----------------------------------------------------
| K | | |
| K | | |
----------------------------------------------------
. , , K " " ( ) . , NFBC ( - ).
, :
--------------------------- -------------------------------
| | | | | _ |
--------------------------- -------------------------------
| N | | | N | |
| N | | | N | |
| K | | | K | |
| K | | | K | |
--------------------------- -------------------------------
, :
- _ .
->> ->> _
, ,
|
|
|
->> | _
, , .
:
4NF BCNF , .
SQL. .
, , . , . , .
1. , 2006 . (.10.2).
10.2. ( 1)
2. : , 1000. , * (. .10.3). , , .
.10.3.
, QBE, SQL, . Access SQL . , SQL, . SQL : . .
SQL . QBE. , SQL , . , , , SQL.
C SQL , Access. SQL:
select - SQL, . select , . * select, ;
distinct , SQL;
distinctrow ;
from , ( ) ;
join - , ;
where , ;
order by ( , desc);
group by , . group by select, avg, count, sum .
|
|
|
; -, SQL .
, and or, : between, in, like.
SQL . 1. SQL, , : = * _
Select distinctrow.,
._,
[]*[_] as
from;
2. .
select *
from
where month(_) = 3;
3. , 2, .
select *
from
where month(_) = 3
order by _;
4. , .
select distinctrow._,
sum([]*[_]) as
from
group by _;
5. 31 2006.
select *
from
where _ = #3/31/06#;
6. .
select *
from
where =[ ];
