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Berkeley DB的基本使用

在下載安裝這個數據庫之后，來使用這樣的數據庫做一個例子。
1.創建一個數據庫

#include? < db_cxx.h >

#include? < iostream >

#include? < string >

using ? namespace ?std;

int ?main( int ?, char ? * [])

{

???? try

???? {

????????Db?db(NULL,NULL);

???????? //

???????? // ?d:\\MyTest.db????數據文件目錄

???????? // ?DB_BTREE????????????使用的文件保存的結構

???????? // ?DB_CREATE????????創建方式的打開

???????? // ?NULL????????????????在windows里不使用此結構

???????? //

???????? if ?( 0 ? == ?db.open(NULL, " d:\\MyTest.db " , " MyFirstDB " ,DB_BTREE,DB_CREATE,NULL))

???????? {

????????????cout << " 創建數據庫文件! " << endl;

????????}

????}

???? catch ?(DbException? & e)

???? {

????????cout << " 創建數據庫失敗: " ;

????????cout << e.what() << endl;

????}

????

???? return ? 0 ;

}

2.向數據庫里保存一個記錄

#include? < iostream >

#include? < db_cxx.h >

using ? namespace ?std;

typedef?unsigned? int ?UINT32,? * PUINT32?;

typedef?unsigned? char ?UINT8,? * PUINT8?;

#pragma?pack(push,? 1 )

typedef? struct ?_SMyUser

{

????UINT32?userID;

???? char ?name[ 32 ];

} SMyUser;

#pragma?pack(pop)

void ?main()

{

???? try

???? {

????????Db?db(NULL,NULL);

???????? if ?(db.open(NULL, " d:\\MyTest.db " , " MyFirstDB " ,DB_BTREE,DB_RDONLY,NULL)? == ? 0 )

???????? {

????????????SMyUser?resInst;

????????????memset( & resInst, 0 , sizeof (SMyUser));

????????????resInst.userID = 1 ;

????????????Dbt?dbKey( & (resInst.userID), sizeof (resInst.userID));

????????????Dbt?dbData;

????????????memset( & dbData, 0 , sizeof (dbData));

???????????? // Dbt?dbData(&resInst,sizeof(resInst));

???????????? if ?( 0 == db. get (NULL, & dbKey, & dbData, 0 ))

???????????? {

????????????????cout << " 增加成功 " << endl;

????????????????SMyUser? * pResInst = (SMyUser * )dbData.get_data();

????????????????cout << " 內容: " << ( char * )pResInst -> name << endl;

????????????}

????????}

????}

???? catch ?(DbException? & e)

???? {

????????cout << " 失敗: " << e.what() << endl;

????}

????cout << " hello?the?world " << endl;

}

3.從數據庫里檢索出數據

#include? < iostream >

#include? < db_cxx.h >

using ? namespace ?std;

typedef?unsigned? int ?UINT32,? * PUINT32?;

typedef?unsigned? char ?UINT8,? * PUINT8?;

#pragma?pack(push,? 1 )

typedef? struct ?_SMyUser

{

????UINT32?userID;

???? char ?name[ 32 ];

} SMyUser;

#pragma?pack(pop)

void ?main()

{

???? try

???? {

????????Db?db(NULL,NULL);

???????? if ?(db.open(NULL, " d:\\MyTest.db " , " MyFirstDB " ,DB_BTREE,DB_RDONLY,NULL)? == ? 0 )

???????? {

????????????SMyUser?resInst;

????????????memset( & resInst, 0 , sizeof (SMyUser));

????????????resInst.userID = 1 ;

????????????Dbt?dbKey( & (resInst.userID), sizeof (resInst.userID));

????????????Dbt?dbData;

????????????memset( & dbData, 0 , sizeof (dbData));

???????????? // Dbt?dbData(&resInst,sizeof(resInst));

???????????? if ?( 0 == db. get (NULL, & dbKey, & dbData, 0 ))

???????????? {

????????????????cout << " 增加成功 " << endl;

????????????????SMyUser? * pResInst = (SMyUser * )dbData.get_data();

????????????????cout << " 內容: " << ( char * )pResInst -> name << endl;

????????????}

????????}

????}

???? catch ?(DbException? & e)

???? {

????????cout << " 失敗: " << e.what() << endl;

????}

????cout << " hello?the?world " << endl;

}

4.刪除一條記錄

#include? < iostream >

#include? < db_cxx.h >

using ? namespace ?std;

typedef?unsigned? int ?UINT32,? * PUINT32?;

typedef?unsigned? char ?UINT8,? * PUINT8?;

#pragma?pack(push,? 1 )

typedef? struct ?_SMyUser

{

????UINT32?userID;

???? char ?name[ 32 ];

} SMyUser;

#pragma?pack(pop)

int ?main()

{

???? try

???? {

????????Db?db(NULL,NULL);

???????? if ?(db.open(NULL, " d:\\MyTest.db " , " MyFirstDB " ,DB_BTREE,NULL,NULL)? == ? 0 )

???????? {

????????????SMyUser?resInst;

????????????memset( & resInst, 0 , sizeof (SMyUser));

????????????resInst.userID = 1 ;

????????????Dbt?dbKey( & (resInst.userID), sizeof (resInst.userID));

????????????

???????????? if ?( 0 == db.del(NULL, & dbKey, 0 ))

???????????? {

????????????????cout << " 增加成功 " << endl;

????????????}

????????}

????}

???? catch ?(DbException? & e)

???? {

????????cout << " 失敗: " << e.what() << endl;

????}

???? return ? 0 ;

}

這一些東西都是一些基本的操作。主要是想說明這個Berkeley DB是很強調一個這樣的概念：key與Data。他們都是一個很原始buffer塊。基于這一個數據庫的基礎，我們可自己做一些工作，其實有一些像自己去實現一數據庫出來。這個上面的MyFirstDB這個東東，感覺上真的是像一個表。

[Sword.Hell]

posted on 2006-12-14 11:14 Sword.Hell blog 閱讀(1602) 評論(1) 編輯收藏引用所屬分類: 使用Berkeley DB

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相關文章: Berkeley DB的基本使用 Berkeley DB網上的資源 Berkeley DB概述(轉2) Berkeley DB概述(轉1)

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