C ++ SQL数据库程序
时间：2020-03-06 14:55:33 来源:igfitidea点击:
我有以下编写的代码，但SQLBindCol似乎无法正常工作(当然，我也可能搞砸了整个程序！它们在SQL企业管理器中看起来都很不错。因此，在注释"第3部分和第4部分：基于条件的搜索"之后，我需要帮助。也许我应该完成完全不同的任务，或者这是可以接受的方法？
#include <iostream>
#include <cstdio>
#include <string>
#include <windows.h>
#include <sql.h>
#include <sqlext.h>
#include <sqltypes.h>
using namespace std; // to save us having to type std::
const int MAX_CHAR = 1024;
int main ( )
{
SQLCHAR SQLStmt[MAX_CHAR];
char strSQL[MAX_CHAR];
char chrTemp;
SQLVARCHAR rtnFirstName[50];
SQLVARCHAR rtnLastName[50];
SQLVARCHAR rtnAddress[30];
SQLVARCHAR rtnCity[30];
SQLVARCHAR rtnState[3];
SQLDOUBLE rtnSalary;
SQLVARCHAR rtnGender[1];
SQLINTEGER rtnAge;
// Get a handle to the database
SQLHENV EnvironmentHandle;
RETCODE retcode = SQLAllocHandle( SQL_HANDLE_ENV, SQL_NULL_HANDLE, &EnvironmentHandle );
// Set the SQL environment flags
retcode = SQLSetEnvAttr( EnvironmentHandle, SQL_ATTR_ODBC_VERSION, (SQLPOINTER) SQL_OV_ODBC3, SQL_IS_INTEGER );
// create handle to the SQL database
SQLHDBC ConnHandle;
retcode = SQLAllocHandle( SQL_HANDLE_DBC, EnvironmentHandle, &ConnHandle );
// Open the database using a System DSN
retcode = SQLDriverConnect(ConnHandle,
NULL,
(SQLCHAR*)"DSN=PRG411;UID=myUser;PWD=myPass;",
SQL_NTS,
NULL,
SQL_NTS,
NULL,
SQL_DRIVER_NOPROMPT);
if (!retcode)
{
cout << "SQLConnect() Failed";
}
else
{
// create a SQL Statement variable
SQLHSTMT StatementHandle;
retcode = SQLAllocHandle(SQL_HANDLE_STMT, ConnHandle, &StatementHandle);
// Part 1: Create the Employee table (Database)
do
{
cout << "Create the new table? ";
cin >> chrTemp;
} while (cin.fail());
if (chrTemp == 'y' || chrTemp == 'Y')
{
strcpy((char *) SQLStmt, "CREATE TABLE [dbo].[Employee]([pkEmployeeID] [int] IDENTITY(1,1) NOT NULL,[FirstName] [varchar](50) NOT NULL,[LastName] [varchar](50) NOT NULL,[Address] [varchar](30) NOT NULL,[City] [varchar](30) NOT NULL,[State] [varchar](3) NOT NULL, [Salary] [double] NOT NULL,[Gender] [varchar](1) NOT NULL, [Age] [int] NOT NULL, CONSTRAINT [PK_Employee] PRIMARY KEY CLUSTERED ([pkEmployeeID] ASC)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]) ON [PRIMARY]");
retcode = SQLExecDirect(StatementHandle, SQLStmt, SQL_NTS);
}
// Part 2: Hardcode records into the table
do
{
cout << "Add records to the table? ";
cin >> chrTemp;
} while (cin.fail());
if (chrTemp == 'y' || chrTemp == 'Y')
{
strcpy((char *) SQLStmt, "INSERT INTO employee([FirstName], [LastName], [Address], [City], [State], [Salary], [Gender],[Age]) VALUES ('Mike','Slentz','123 Torrey Dr.','North Clairmont','CA', 48000.00 ,'M',34)");
retcode = SQLExecDirect(StatementHandle, SQLStmt, SQL_NTS);
strcpy((char *) SQLStmt, "INSERT INTO employee([FirstName], [LastName], [Address], [City], [State], [Salary], [Gender],[Age]) VALUES ('Sue','Vander Hayden','46 East West St.','San Diego','CA', 36000.00 ,'F',28)");
retcode = SQLExecDirect(StatementHandle, SQLStmt, SQL_NTS);
strcpy((char *) SQLStmt, "INSERT INTO employee([FirstName], [LastName], [Address], [City], [State], [Salary], [Gender],[Age]) VALUES ('Sharon','Stonewall','756 West Olive Garden Way','Plymouth','MA', 56000.00 ,'F',58)");
retcode = SQLExecDirect(StatementHandle, SQLStmt, SQL_NTS);
strcpy((char *) SQLStmt, "INSERT INTO employee([FirstName], [LastName], [Address], [City], [State], [Salary], [Gender],[Age]) VALUES ('James','Bartholemew','777 Praying Way','Falls Church','VA', 51000.00 ,'M',45)");
retcode = SQLExecDirect(StatementHandle, SQLStmt, SQL_NTS);
strcpy((char *) SQLStmt, "INSERT INTO employee([FirstName], [LastName], [Address], [City], [State], [Salary], [Gender],[Age]) VALUES ('Joe','Smith','111 North 43rd Ave','Peoria','AZ', 44000.00 ,'M', 40)");
retcode = SQLExecDirect(StatementHandle, SQLStmt, SQL_NTS);
strcpy((char *) SQLStmt, "INSERT INTO employee([FirstName], [LastName], [Address], [City], [State], [Salary], [Gender],[Age]) VALUES ('Michael','Smith','20344 North Swan Park','Phoenix','AZ', 24000.00 ,'M', 40)");
retcode = SQLExecDirect(StatementHandle, SQLStmt, SQL_NTS);
strcpy((char *) SQLStmt, "INSERT INTO employee([FirstName], [LastName], [Address], [City], [State], [Salary], [Gender],[Age]) VALUES ('Jennifer','Jones','123 West North Ave','Flagstaff','AZ', 40000.00 ,'F', 40)");
retcode = SQLExecDirect(StatementHandle, SQLStmt, SQL_NTS);
strcpy((char *) SQLStmt, "INSERT INTO employee([FirstName], [LastName], [Address], [City], [State], [Salary], [Gender],[Age]) VALUES ('Cora','York','33rd Park Way Drive','Mayville','MI', 30000.00 ,'F', 61)");
retcode = SQLExecDirect(StatementHandle, SQLStmt, SQL_NTS);
strcpy((char *) SQLStmt, "INSERT INTO employee([FirstName], [LastName], [Address], [City], [State], [Salary], [Gender],[Age]) VALUES ('Tom','Jefferson','234 Friendship Way','Battle Creek','MI', 41000.00 ,'M', 31)");
retcode = SQLExecDirect(StatementHandle, SQLStmt, SQL_NTS);
}
// Part 3 & 4: Searchs based on criteria
do
{
cout << "1. Display all records in the database" << endl;
cout << "2. Display all records with age greater than 40" << endl;
cout << "3. Display all records with salary over K" << endl;
cout << "4. Exit" << endl << endl;
do
{
cout << "Please enter a selection: ";
cin >> chrTemp;
} while (cin.fail());
if (chrTemp == '1')
{
strcpy((char *) SQLStmt, "SELECT [FirstName], [LastName], [Address], [City], [State], [Salary], [Gender],[Age] FROM EMPLOYEE");
}
else if (chrTemp == '2')
{
strcpy((char *) SQLStmt, "SELECT [FirstName], [LastName], [Address], [City], [State], [Salary], [Gender],[Age] FROM EMPLOYEE WHERE [AGE] > 40");
}
else if (chrTemp == '3')
{
strcpy((char *) SQLStmt, "SELECT [FirstName], [LastName], [Address], [City], [State], [Salary], [Gender],[Age] FROM EMPLOYEE WHERE [Salary] > 30000");
}
if (chrTemp == '1' || chrTemp == '2' || chrTemp == '3')
{
retcode = SQLExecDirect(StatementHandle, SQLStmt, SQL_NTS);
SQLBindCol(StatementHandle, 1, SQL_C_CHAR, &rtnFirstName, sizeof(rtnFirstName), NULL );
SQLBindCol(StatementHandle, 2, SQL_C_CHAR, &rtnLastName, sizeof(rtnLastName), NULL );
SQLBindCol(StatementHandle, 3, SQL_C_CHAR, &rtnAddress, sizeof(rtnAddress), NULL );
SQLBindCol(StatementHandle, 4, SQL_C_CHAR, &rtnCity, sizeof(rtnCity), NULL );
SQLBindCol(StatementHandle, 5, SQL_C_CHAR, &rtnState, sizeof(rtnState), NULL );
SQLBindCol(StatementHandle, 6, SQL_C_DOUBLE, &rtnSalary, sizeof(rtnSalary), NULL );
SQLBindCol(StatementHandle, 7, SQL_C_CHAR, &rtnGender, sizeof(rtnGender), NULL );
SQLBindCol(StatementHandle, 8, SQL_C_NUMERIC, &rtnAge, sizeof(rtnAge), NULL );
for(;;)
{
retcode = SQLFetch(StatementHandle);
if (retcode == SQL_NO_DATA_FOUND) break;
cout << rtnFirstName << " " << rtnLastName << " " << rtnAddress << " " << rtnCity << " " << rtnState << " " << rtnSalary << " " << rtnGender << "" << rtnAge << endl;
}
}
} while (chrTemp != '4');
SQLFreeStmt(StatementHandle, SQL_CLOSE );
SQLFreeConnect(ConnHandle);
SQLFreeEnv(EnvironmentHandle);
printf( "Done.\n" );
}
return 0;
}
解决方案
我们可以从SQL中获得足够的诊断，从而可以隔离和解决问题。
当SQLExecDirect返回" SQL_SUCCESS"或者" SQL_SUCCESS_WITH_INFO"以外的其他值时，可以调用该语句句柄来告诉我们它出了什么问题。
SQLGetDiagRec(SQL_HANDLE_STMT，StatementHandle，req，state，＆error，(SQLCHAR *)缓冲区，(SQLINTEGER)MAX_CHAR，(SQLSMALLINT *)＆output_length);`
当然，我们必须分配我们在此处看到的变量……我建议我们在SQLGetDiagRec调用之后放置一条废线，并为其分配一个断点。当它中断时，我们可以查看state的值：它将与此处的"诊断"部分保持一致：
http://msdn.microsoft.com/zh-CN/library/ms713611(VS.85).aspx
好的，这是现在可以使用的代码...
using namespace std; // to save us having to type std::
const int MAX_CHAR = 1024;
int main ( )
{
SQLSMALLINT RecNumber;
SQLCHAR * SQLState;
SQLINTEGER * NativeErrorPtr;
SQLCHAR * MessageText;
SQLSMALLINT BufferLength;
SQLSMALLINT * TextLengthPtr;
SQLCHAR SQLStmt[MAX_CHAR];
char strSQL[MAX_CHAR];
char chrTemp;
SQLVARCHAR rtnFirstName[50];
SQLVARCHAR rtnLastName[50];
SQLVARCHAR rtnAddress[30];
SQLVARCHAR rtnCity[30];
SQLVARCHAR rtnState[3];
SQLDOUBLE rtnSalary;
SQLVARCHAR rtnGender[2];
SQLINTEGER rtnAge;
// Get a handle to the database
SQLHENV EnvironmentHandle;
RETCODE retcode = SQLAllocHandle( SQL_HANDLE_ENV, SQL_NULL_HANDLE, &EnvironmentHandle );
// Set the SQL environment flags
retcode = SQLSetEnvAttr( EnvironmentHandle, SQL_ATTR_ODBC_VERSION, (SQLPOINTER) SQL_OV_ODBC3, SQL_IS_INTEGER );
// create handle to the SQL database
SQLHDBC ConnHandle;
retcode = SQLAllocHandle( SQL_HANDLE_DBC, EnvironmentHandle, &ConnHandle );
// Open the database using a System DSN
retcode = SQLDriverConnect(ConnHandle,
NULL,
(SQLCHAR*)"DSN=PRG411;UID=myUser;PWD=myPass;",
SQL_NTS,
NULL,
SQL_NTS,
NULL,
SQL_DRIVER_NOPROMPT);
if (!retcode)
{
cout << "SQLConnect() Failed";
}
else
{
// create a SQL Statement variable
SQLHSTMT StatementHandle;
retcode = SQLAllocHandle(SQL_HANDLE_STMT, ConnHandle, &StatementHandle);
// Part 1: Create the Employee table (Database)
do
{
cout << "Create the new table? ";
cin >> chrTemp;
} while (cin.fail());
if (chrTemp == 'y' || chrTemp == 'Y')
{
strcpy((char *) SQLStmt, "CREATE TABLE [dbo].[Employee]([pkEmployeeID] [int] IDENTITY(1,1) NOT NULL,[FirstName] [varchar](50) NOT NULL,[LastName] [varchar](50) NOT NULL,[Address] [varchar](30) NOT NULL,[City] [varchar](30) NOT NULL,[State] [varchar](3) NOT NULL, [Salary] [decimal] NOT NULL,[Gender] [varchar](1) NOT NULL, [Age] [int] NOT NULL, CONSTRAINT [PK_Employee] PRIMARY KEY CLUSTERED ([pkEmployeeID] ASC)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]) ON [PRIMARY]");
retcode = SQLExecDirect(StatementHandle, SQLStmt, SQL_NTS);
}
// Part 2: Hardcode records into the table
do
{
cout << "Add records to the table? ";
cin >> chrTemp;
} while (cin.fail());
if (chrTemp == 'y' || chrTemp == 'Y')
{
strcpy((char *) SQLStmt, "INSERT INTO employee([FirstName], [LastName], [Address], [City], [State], [Salary], [Gender],[Age]) VALUES ('Mike','Slentz','123 Torrey Dr.','North Clairmont','CA', 48000.00 ,'M',34)");
retcode = SQLExecDirect(StatementHandle, SQLStmt, SQL_NTS);
strcpy((char *) SQLStmt, "INSERT INTO employee([FirstName], [LastName], [Address], [City], [State], [Salary], [Gender],[Age]) VALUES ('Sue','Vander Hayden','46 East West St.','San Diego','CA', 36000.00 ,'F',28)");
retcode = SQLExecDirect(StatementHandle, SQLStmt, SQL_NTS);
strcpy((char *) SQLStmt, "INSERT INTO employee([FirstName], [LastName], [Address], [City], [State], [Salary], [Gender],[Age]) VALUES ('Sharon','Stonewall','756 West Olive Garden Way','Plymouth','MA', 56000.00 ,'F',58)");
retcode = SQLExecDirect(StatementHandle, SQLStmt, SQL_NTS);
strcpy((char *) SQLStmt, "INSERT INTO employee([FirstName], [LastName], [Address], [City], [State], [Salary], [Gender],[Age]) VALUES ('James','Bartholemew','777 Praying Way','Falls Church','VA', 51000.00 ,'M',45)");
retcode = SQLExecDirect(StatementHandle, SQLStmt, SQL_NTS);
strcpy((char *) SQLStmt, "INSERT INTO employee([FirstName], [LastName], [Address], [City], [State], [Salary], [Gender],[Age]) VALUES ('Joe','Smith','111 North 43rd Ave','Peoria','AZ', 44000.00 ,'M', 40)");
retcode = SQLExecDirect(StatementHandle, SQLStmt, SQL_NTS);
strcpy((char *) SQLStmt, "INSERT INTO employee([FirstName], [LastName], [Address], [City], [State], [Salary], [Gender],[Age]) VALUES ('Michael','Smith','20344 North Swan Park','Phoenix','AZ', 24000.00 ,'M', 40)");
retcode = SQLExecDirect(StatementHandle, SQLStmt, SQL_NTS);
strcpy((char *) SQLStmt, "INSERT INTO employee([FirstName], [LastName], [Address], [City], [State], [Salary], [Gender],[Age]) VALUES ('Jennifer','Jones','123 West North Ave','Flagstaff','AZ', 40000.00 ,'F', 40)");
retcode = SQLExecDirect(StatementHandle, SQLStmt, SQL_NTS);
strcpy((char *) SQLStmt, "INSERT INTO employee([FirstName], [LastName], [Address], [City], [State], [Salary], [Gender],[Age]) VALUES ('Cora','York','33rd Park Way Drive','Mayville','MI', 30000.00 ,'F', 61)");
retcode = SQLExecDirect(StatementHandle, SQLStmt, SQL_NTS);
strcpy((char *) SQLStmt, "INSERT INTO employee([FirstName], [LastName], [Address], [City], [State], [Salary], [Gender],[Age]) VALUES ('Tom','Jefferson','234 Friendship Way','Battle Creek','MI', 41000.00 ,'M', 31)");
retcode = SQLExecDirect(StatementHandle, SQLStmt, SQL_NTS);
}
// Part 3 & 4: Searchs based on criteria
do
{
cout << "1. Display all records in the database" << endl;
cout << "2. Display all records with age 40 or over" << endl;
cout << "3. Display all records with salary K or over" << endl;
cout << "4. Exit" << endl << endl;
do
{
cout << "Please enter a selection: ";
cin >> chrTemp;
} while (cin.fail());
if (chrTemp == '1')
{
strcpy((char *) SQLStmt, "SELECT [FirstName], [LastName], [Address], [City], [State], [Salary], [Gender],[Age] FROM EMPLOYEE");
}
else if (chrTemp == '2')
{
strcpy((char *) SQLStmt, "SELECT [FirstName], [LastName], [Address], [City], [State], [Salary], [Gender],[Age] FROM EMPLOYEE WHERE [AGE] >= 40");
}
else if (chrTemp == '3')
{
strcpy((char *) SQLStmt, "SELECT [FirstName], [LastName], [Address], [City], [State], [Salary], [Gender],[Age] FROM EMPLOYEE WHERE [Salary] >= 30000");
}
if (chrTemp == '1' || chrTemp == '2' || chrTemp == '3')
{
retcode = SQLExecDirect(StatementHandle, SQLStmt, SQL_NTS);
//SQLGetDiagRec(SQL_HANDLE_STMT, StatementHandle, RecNumber, SQLState, NativeErrorPtr, (SQLCHAR*) MessageText, (SQLINTEGER) BufferLength, (SQLSMALLINT*) &TextLengthPtr);
SQLBindCol(StatementHandle, 1, SQL_C_CHAR, &rtnFirstName, sizeof(rtnFirstName), NULL );
SQLBindCol(StatementHandle, 2, SQL_C_CHAR, &rtnLastName, sizeof(rtnLastName), NULL );
SQLBindCol(StatementHandle, 3, SQL_C_CHAR, &rtnAddress, sizeof(rtnAddress), NULL );
SQLBindCol(StatementHandle, 4, SQL_C_CHAR, &rtnCity, sizeof(rtnCity), NULL );
SQLBindCol(StatementHandle, 5, SQL_C_CHAR, &rtnState, sizeof(rtnState), NULL );
SQLBindCol(StatementHandle, 6, SQL_C_DOUBLE, &rtnSalary, sizeof(rtnSalary), NULL );
SQLBindCol(StatementHandle, 7, SQL_C_CHAR, &rtnGender, sizeof(rtnGender), NULL );
SQLBindCol(StatementHandle, 8, SQL_C_LONG, &rtnAge, sizeof(rtnAge), NULL );
for(;;)
{
retcode = SQLFetch(StatementHandle);
if (retcode == SQL_NO_DATA_FOUND) break;
cout << rtnFirstName << " " << rtnLastName << " " << rtnAddress << " " << rtnCity << " " << rtnState << " " << rtnSalary << " " << rtnGender << " " << rtnAge << endl;
}
SQLFreeStmt(StatementHandle, SQL_CLOSE);
}
} while (chrTemp != '4');
SQLFreeStmt(StatementHandle, SQL_CLOSE );
SQLFreeHandle(SQL_HANDLE_STMT, StatementHandle);
SQLDisconnect(ConnHandle);
SQLFreeHandle(SQL_HANDLE_DBC, ConnHandle);
SQLFreeHandle(SQL_HANDLE_ENV, EnvironmentHandle);
printf( "Done.\n" );
}
return 0;
}
我们说我们在以下方面遇到错误：
string sqlString ="选择*来自客户，其中Customers.Employee ='" + id +"'";
很明显，对不起，大声笑。 ID是整数，确定。但是，当我们评估字符串时，它像这样出现：
string sqlString ="选择*从客户中，如果Customers.Employee ='100'"；
注意到出什么事了吗？我们周围有单引号。因此，无论使用哪种数据类型，单引号都会使SQL将其视为字符串。因此，像这样将它们取出：
string sqlString ="选择来自客户，其中Customer.Employee =" + id +"";
。 。 。 。 。 。 。或者，
字符串sqlString ="从客户那里选择Wheres.Customers.Employee =" + id;
我的问题是...我们能解释一下C ++中记录的循环工作原理吗？例如，用户向strUName输入用户名，并且我们想查看该用户名是否在数据库表Users中。 SQL很容易(从[UName] ='" + strUName +"'的用户中选择*；但是如何在C ++中实际执行它并弄清楚呢？
我看到了SQLStmt，看到它正在使用Direct执行。然后，我看到一些SQLBindCol垃圾，然后是一个无限循环，直到破坏evals。但是我不太了解正在发生的事情(这对我来说对于任何其他语言来说都很容易，但是我对C ++还是陌生的。
