在C語言中，要連接MySQL數(shù)據(jù)庫可以使用ODBC（Open Database Connectivity）技術(shù)。ODBC是一種將應(yīng)用程序與數(shù)據(jù)存儲在不同廠商的數(shù)據(jù)庫中進行交互的標準。以下是使用ODBC庫在C語言中連接MySQL服務(wù)器的示例代碼：

#include#include#include#define SQL_RESULT_LEN 240
#define SQL_RETURN_CODE_LEN 1000
int main() {
SQLHANDLE sqlenvhandle;
SQLHANDLE sqlconnectionhandle;
SQLHANDLE sqlstatementhandle;
SQLRETURN retcode;
char sqlquery[SQL_RETURN_CODE_LEN] = "SELECT * FROM table_name";
SQLCHAR retconstring[SQL_RETURN_CODE_LEN];
SQLCHAR sqlversion[] = "SQL Server Native Client 11.0";
retcode = SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE, &sqlenvhandle);
if (retcode != SQL_SUCCESS && retcode != SQL_SUCCESS_WITH_INFO) {
printf("Error allocating environment handle\n");
return 0;
}
retcode = SQLSetEnvAttr(sqlenvhandle, SQL_ATTR_ODBC_VERSION, (SQLPOINTER)SQL_OV_ODBC3, 0);
if (retcode != SQL_SUCCESS && retcode != SQL_SUCCESS_WITH_INFO) {
printf("Error setting environment attribute\n");
return 0;
}
retcode = SQLAllocHandle(SQL_HANDLE_DBC, sqlenvhandle, &sqlconnectionhandle);
if (retcode != SQL_SUCCESS && retcode != SQL_SUCCESS_WITH_INFO) {
printf("Error allocating connection handle\n");
return 0;
}
//連接參數(shù)
SQLCHAR connection_string[] = "DRIVER={MySQL ODBC 5.3 Driver};SERVER=localhost;DATABASE=test;UID=root;PWD=123456;";
retcode = SQLDriverConnect(sqlconnectionhandle, NULL, (SQLCHAR*)connection_string, SQL_NTS, retconstring, SQL_RETURN_CODE_LEN, NULL, SQL_DRIVER_COMPLETE);
if (retcode != SQL_SUCCESS && retcode != SQL_SUCCESS_WITH_INFO) {
printf("Error connecting to database\n");
return 0;
}
retcode = SQLAllocHandle(SQL_HANDLE_STMT, sqlconnectionhandle, &sqlstatementhandle);
if (retcode != SQL_SUCCESS && retcode != SQL_SUCCESS_WITH_INFO) {
printf("Error allocating statement handle\n");
return 0;
}
retcode = SQLExecDirect(sqlstatementhandle, (SQLCHAR*)sqlquery, SQL_NTS);
if (retcode != SQL_SUCCESS && retcode != SQL_SUCCESS_WITH_INFO) {
printf("Error executing query\n");
return 0;
}
SQLCHAR name[SQL_RESULT_LEN];
while (SQLFetch(sqlstatementhandle) == SQL_SUCCESS) {
SQLGetData(sqlstatementhandle, 1, SQL_C_CHAR, name, SQL_RESULT_LEN, NULL);
printf("%s", name);
}
SQLFreeHandle(SQL_HANDLE_STMT, sqlstatementhandle);
SQLDisconnect(sqlconnectionhandle);
SQLFreeHandle(SQL_HANDLE_DBC, sqlconnectionhandle);
SQLFreeHandle(SQL_HANDLE_ENV, sqlenvhandle);
return 0;
}

在上述代碼中，首先通過SQLAllocHandle函數(shù)分配環(huán)境句柄、連接句柄和語句句柄。然后通過SQLSetEnvAttr函數(shù)設(shè)置ODBC版本。接著通過SQLDriverConnect函數(shù)連接數(shù)據(jù)庫，并將連接字符串傳遞給函數(shù)。最后通過SQLExecDirect函數(shù)執(zhí)行查詢，并通過SQLFetch和SQLGetData函數(shù)獲取查詢結(jié)果。