在下載安裝這個數(shù)據(jù)庫之后，來使用這樣的數(shù)據(jù)庫做一個例子。
1.創(chuàng)建一個數(shù)據(jù)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(shù)據(jù)文件目錄
???????? // ?DB_BTREE????????????使用的文件保存的結(jié)構(gòu)
???????? // ?DB_CREATE????????創(chuàng)建方式的打開
???????? // ?NULL????????????????在windows里不使用此結(jié)構(gòu)
???????? //
???????? if ?( 0 ? == ?db.open(NULL, " d:\\MyTest.db " , " MyFirstDB " ,DB_BTREE,DB_CREATE,NULL))
???????? {
????????????cout << " 創(chuàng)建數(shù)據(jù)庫文件! " << endl;
????????}
????}
???? catch ?(DbException? & e)
???? {
????????cout << " 創(chuàng)建數(shù)據(jù)庫失敗: " ;
????????cout << e.what() << endl;
????}
????
???? return ? 0 ;
}

2.向數(shù)據(jù)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(nèi)容: " << ( char * )pResInst -> name << endl;
????????????}
????????}
????}
???? catch ?(DbException? & e)
???? {
????????cout << " 失敗: " << e.what() << endl;
????}
????cout << " hello?the?world " << endl;
}

3.從數(shù)據(jù)庫里檢索出數(shù)據(jù)

#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(nèi)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(qiáng)調(diào)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(shù)據(jù)庫的基礎(chǔ)，我們可自己做一些工作，其實有一些像自己去實現(xiàn)一數(shù)據(jù)庫出來。這個上面的MyFirstDB這個東東，感覺上真的是像一個表。



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