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   TheLenka

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 LiveInternet.ru:
: 03.01.2009
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. . n- ,

, 09 2010 . 11:05 +

. .

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(), , ..

60-70 . , IBM IMS, IBM System/360, System/370. . XML.

2) DELETE SQL. . . .

DELETE FROM "table_name" WHERE {condition}

: DELETE FROM Store_Information WHERE store_name = ‘Los Angeles’; - , store_name- Los Angeles.

3) : -, .

, (, , , ). 6 : ( 1). . . - (). . , - (5NF PJ/NF).

: - (_, _, _, _) : _, _; _, _ : _ -> C_; _ -> _; _ -> C_; _ -> _; _, _ -> C_; _, _ -> C_

 

, , . - 3NF. , , , . , , , , . - , .

- R - (BCNF) , . , -. -: (_, _) : _; _ : _ -> C_; _ -> _; - (_, _, _) : _, _ : _, _ -> C_

, _. - BCNF, .

: (_,_, _)

, , , , . , . , , , ( , , , , ). _, _, _, . , BCNF. : , , , , .

R (A, B, C) R.A -> -> R.B , B, A C, A . : _ -> -> _; _ -> -> _

, R (A, B, C) R.A -> -> R.B , R.A -> -> R.C.

R (4NF) , A -> -> B R A.

- -:

- (_, _)

- (_, _)

4NF .

. , , – , .

, , 3, . - . , – , .. , , .

 

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