怎么通过ODBC把数据库与C语言联系起来，调用数据库的内容

#ifndef ___LIB_DB___

#define ___LIB_DB___

extern int DB_Open(char * dbcn, char * usr, char * pwd)

extern int DB_Exec(char * sql)

extern void * DB_Query(char *sql, const char *fmt, ...)

extern int DB_Next(void * hRecordset)

extern void DB_CleanQuery(void *hRecordset)

extern int DB_Close(void)

#endif

#ifdef WIN32

#include <windows.h>

#include <odbcinst.h>

#include <sqlext.h>

#else

#include <mysql.h>

#include <unistd.h>

#define SQLHANDLE static MYSQL

#endif

#include <stdarg.h>

#include <stdlib.h>

#include <stdio.h>

#include <string.h>

SQLHANDLE hDBEnv, hDBC

int DB_Open(char * dbcn, char * usr, char * pwd)

{

int r

#ifdef WIN32

r = SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE, &hDBEnv)

if(r) return 0

r = SQLSetEnvAttr(hDBEnv,SQL_ATTR_ODBC_VERSION,

(void*)SQL_OV_ODBC3,0)

if(r) return 0

r = SQLAllocHandle(SQL_HANDLE_DBC, hDBEnv, &hDBC)

if(r) return 0

r = SQLConnect(hDBC,

(unsigned char *)dbcn, strlen(dbcn),

(unsigned char *)usr, strlen(usr),

(unsigned char *)pwd, strlen(pwd))

return r==SQL_SUCCESS || r==SQL_SUCCESS_WITH_INFO

#else

mysql_init(&hDBC)

MYSQL * rx = mysql_real_connect(

&hDBC, dbcn, usr, pwd, NULL, 0, NULL, 0)

if(!rx) return 0

return 1

#endif

}//end DB_Open

int DB_Exec(char * sql)

{

#ifdef WIN32

SQLHANDLE hStatement = NULL

SQLAllocHandle(SQL_HANDLE_STMT, hDBC, &hStatement)

SQLExecDirect(hStatement,(unsigned char *)sql, strlen(sql))

SQLCloseCursor(hStatement)

SQLFreeHandle(SQL_HANDLE_STMT, hStatement)

hStatement = NULL

#else

mysql_real_query (&hDBC, sql, strlen(sql))

#endif

return 1

}//end DB_Exec

int DB_Close(void)

{

#ifdef WIN32

SQLDisconnect(hDBC)

SQLFreeHandle(SQL_HANDLE_DBC, hDBC)

SQLFreeHandle(SQL_HANDLE_ENV, hDBEnv)

#else

mysql_close(&hDBC)

#endif

return 1

}//DB_Close()

#ifndef WIN32

typedef struct tagMySQLRecordset {

MYSQL_RES * hRecord

void * * row

int * size

int cols

} MYSQLRecordset

#endif

void DB_CleanQuery(void *hRecordset)

{

if(!hRecordset) return

#ifdef WIN32

__try {

SQLCloseCursor(hRecordset)

SQLFreeHandle(SQL_HANDLE_STMT, hRecordset)

hRecordset = NULL

}__finally{

return

}//end try

#else

MYSQLRecordset * hRec = (MYSQLRecordset *) hRecordset

mysql_free_result (hRec->hRecord)

free(hRec->row) hRec->row = NULL

free(hRec->size)hRec->size = NULL

free(hRec)hRec = NULL

#endif

}//end DB_CleanQuery

int DB_Next(void * hRecordset)

{

int r=0if(!hRecordset) return 0

#ifdef WIN32

r = SQLFetch(hRecordset)

r = r == SQL_SUCCESS || r == SQL_SUCCESS_WITH_INFO

if(!r) {

DB_CleanQuery(hRecordset)

}//end if

#else

MYSQLRecordset * hRec = (MYSQLRecordset *) hRecordset

MYSQL_ROW row = mysql_fetch_row (hRec->hRecord)

if(row) {

for(int i=0i<hRec->colsi++) {

memcpy(hRec->row[i], row[i], hRec->size[i])

}//next i

r = 1

}else{

DB_CleanQuery(hRecordset)

r = 0

}//end if

#endif

return r

}//end DB_Next

int DB_params_count(const char * fmt)

{

int i=0, j=0

while(fmt[i]) {

if(fmt[i]=='%') j++

i++

}//end while

return j

}//end DB_params_count

void * DB_Query(char *sql, const char *fmt, ...)

{

int r=0

int cols = DB_params_count(fmt)

if(cols<1) return NULL

#ifdef WIN32

SQLHANDLE hStatement = NULL

SQLAllocHandle(SQL_HANDLE_STMT, hDBC, &hStatement)

r = SQLExecDirect(hStatement,(unsigned char *)sql, strlen(sql))

r = r==SQL_SUCCESS || r == SQL_SUCCESS_WITH_INFO

if(!r) {

return NULL

}//end if

#else

r = mysql_real_query (&hDBC, sql, strlen(sql))

if(r) return NULL

MYSQL_RES * rec = NULL

rec = mysql_store_result (&hDBC)

if(!rec) return NULL

MYSQLRecordset * hStatement

= (MYSQLRecordset *)malloc(sizeof(MYSQLRecordset))

if(!hStatement) return NULL

memset(hStatement, 0, sizeof(MYSQLRecordset))

hStatement->hRecord = rec

hStatement->cols = cols

hStatement->row = (void **)malloc(cols * sizeof(void *))

memset(hStatement->row, 0, cols * sizeof(void *))

hStatement->size = (int *)malloc(cols * sizeof(int))

memset(hStatement->size, 0, cols * sizeof(int))

#endif

va_list apva_start(ap, fmt)

void * varchar buf[32]

int i=0,j=0,k=0,sz=0char c=0

int len = strlen(fmt)int bad=1

#ifdef WIN32

int col=1

#else

int col=0

#endif

while(fmt[i]) {

c = fmt[i++]

if(c != '%') continue

c = fmt[i++]

var = va_arg(ap, void *)

if(c == 'd') {

#ifdef WIN32

SQLBindCol(hStatement, col, SQL_C_SLONG, var, 4,NULL)

#else

hStatement->row[col] = var

hStatement->size[col] = sizeof(long)

#endif

col++

continue

}//end if

if(c == 'f') {

#ifdef WIN32

SQLBindCol(hStatement, col, SQL_C_FLOAT, var, 4,NULL)

#else

hStatement->row[col] = var

hStatement->size[col] = sizeof(float)

#endif

col++

continue

}//end if

memset(buf, 0, 32)bad=1

for(j=i-1j<lenj++) {

c = fmt[j]

if(c>='0' &&c<='9') buf[j-i+1]=c

if(c=='s') {bad=0k=j+1break}

}//next j

if(bad) return NULL

sscanf(buf, "%d", &sz)

#ifdef WIN32

SQLBindCol(hStatement, col, SQL_C_CHAR, var, sz, NULL)

#else

hStatement->row[col] = var

hStatement->size[col] = sz

#endif

col++

i = k

}//end while

va_end(ap)

return hStatement

}//end DB_Rec

#include <icrsint.h>

#include<iostream>

#include<iomanip>

#include <string>

using namespace std

#import "c:\program files\common files\system\ado\msado15.dll" no_namespace rename("EOF", "adoEOF")

void main()

{

CoInitialize(NULL)

_ConnectionPtr sqlSp

HRESULT hr=sqlSp.CreateInstance(_uuidof(Connection))

if(FAILED(hr))

{

cout<<"_ConnectionPtr对象指针实例化失败！！！"<<endl

return

}

else {

try {

_bstr_t strConnect="Driver={sql server}server=127.0.0.1,1433uid=sapwd=1234567890database=test"

sqlSp->Open(strConnect,"","",adModeUnknown)

}

catch(_com_error &e) {

cout<<e.Description()<<endl

}

_RecordsetPtr m_pRecordset

if(FAILED(m_pRecordset.CreateInstance( _uuidof( Recordset ))))

{

cout<<"记录集对象指针实例化失败！"<<endl

return

}

try {

m_pRecordset->Open("select * from T_Test",(IDispatch*)sqlSp,adOpenDynamic,adLockOptimistic, adCmdText)

}

catch (_com_error &e)

{

cout <<e.Description()<<endl

}

try {

m_pRecordset->MoveFirst()

while(!m_pRecordset->adoEOF)

{

string insertTime=(char*)(_bstr_t)(m_pRecordset->Fields->GetItem(_variant_t("InsertTime"))->Value)

cout<<insertTime<<endl

m_pRecordset->MoveNext()

}

}

catch (_com_error &e)

{

cout <<e.Description()<<endl

}

}

system("pause")

}

c语言是计算机编程的基础语言.

数据库是用做项目时存放数据的一个系统.如网站有它的数据库.游戏也有它的数据库.软件就是从数据库里调用数据.因此很重要.

数据结构就是一些算法思想的东西.有很强的逻辑性.用好能在很大程度上提高软件或系统的性能.不过非常的抽象.数据结构可以用多种语言来表示.C,或C++.

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