ADO如何通过预编译提高性能,用C++写出一个例子
时间: 2023-04-10 19:01:50 浏览: 76
对于这个问题,我可以回答。ADO可以通过预编译SQL语句来提高性能。下面是一个用C语言编写的例子:
```
#include <stdio.h>
#include <stdlib.h>
#include <windows.h>
#include <sql.h>
#include <sqlext.h>
int main()
{
SQLHENV env;
SQLHDBC dbc;
SQLHSTMT stmt;
SQLRETURN ret;
SQLCHAR *sql = (SQLCHAR *)"SELECT * FROM table WHERE id = ?";
SQLINTEGER id = 1;
// Allocate environment handle
ret = SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE, &env);
if (ret != SQL_SUCCESS && ret != SQL_SUCCESS_WITH_INFO) {
printf("Failed to allocate environment handle\n");
return 1;
}
// Set the ODBC version
ret = SQLSetEnvAttr(env, SQL_ATTR_ODBC_VERSION, (SQLPOINTER)SQL_OV_ODBC3, 0);
if (ret != SQL_SUCCESS && ret != SQL_SUCCESS_WITH_INFO) {
printf("Failed to set ODBC version\n");
SQLFreeHandle(SQL_HANDLE_ENV, env);
return 1;
}
// Allocate connection handle
ret = SQLAllocHandle(SQL_HANDLE_DBC, env, &dbc);
if (ret != SQL_SUCCESS && ret != SQL_SUCCESS_WITH_INFO) {
printf("Failed to allocate connection handle\n");
SQLFreeHandle(SQL_HANDLE_ENV, env);
return 1;
}
// Connect to the database
ret = SQLConnect(dbc, (SQLCHAR *)"dsn", SQL_NTS, (SQLCHAR *)"username", SQL_NTS, (SQLCHAR *)"password", SQL_NTS);
if (ret != SQL_SUCCESS && ret != SQL_SUCCESS_WITH_INFO) {
printf("Failed to connect to database\n");
SQLFreeHandle(SQL_HANDLE_DBC, dbc);
SQLFreeHandle(SQL_HANDLE_ENV, env);
return 1;
}
// Allocate statement handle
ret = SQLAllocHandle(SQL_HANDLE_STMT, dbc, &stmt);
if (ret != SQL_SUCCESS && ret != SQL_SUCCESS_WITH_INFO) {
printf("Failed to allocate statement handle\n");
SQLDisconnect(dbc);
SQLFreeHandle(SQL_HANDLE_DBC, dbc);
SQLFreeHandle(SQL_HANDLE_ENV, env);
return 1;
}
// Prepare the SQL statement
ret = SQLPrepare(stmt, sql, SQL_NTS);
if (ret != SQL_SUCCESS && ret != SQL_SUCCESS_WITH_INFO) {
printf("Failed to prepare SQL statement\n");
SQLFreeHandle(SQL_HANDLE_STMT, stmt);
SQLDisconnect(dbc);
SQLFreeHandle(SQL_HANDLE_DBC, dbc);
SQLFreeHandle(SQL_HANDLE_ENV, env);
return 1;
}
// Bind the parameter
ret = SQLBindParameter(stmt, 1, SQL_PARAM_INPUT, SQL_C_LONG, SQL_INTEGER, 0, 0, &id, 0, NULL);
if (ret != SQL_SUCCESS && ret != SQL_SUCCESS_WITH_INFO) {
printf("Failed to bind parameter\n");
SQLFreeHandle(SQL_HANDLE_STMT, stmt);
SQLDisconnect(dbc);
SQLFreeHandle(SQL_HANDLE_DBC, dbc);
SQLFreeHandle(SQL_HANDLE_ENV, env);
return 1;
}
// Execute the SQL statement
ret = SQLExecute(stmt);
if (ret != SQL_SUCCESS && ret != SQL_SUCCESS_WITH_INFO) {
printf("Failed to execute SQL statement\n");
SQLFreeHandle(SQL_HANDLE_STMT, stmt);
SQLDisconnect(dbc);
SQLFreeHandle(SQL_HANDLE_DBC, dbc);
SQLFreeHandle(SQL_HANDLE_ENV, env);
return 1;
}
// Fetch the results
while (SQLFetch(stmt) == SQL_SUCCESS) {
// Process the results
}
// Free the statement handle
SQLFreeHandle(SQL_HANDLE_STMT, stmt);
// Disconnect from the database
SQLDisconnect(dbc);
// Free the connection handle
SQLFreeHandle(SQL_HANDLE_DBC, dbc);
// Free the environment handle
SQLFreeHandle(SQL_HANDLE_ENV, env);
return 0;
}
```