Summary

Reference official website:https://docs.microsoft.com/zh-cn/sql/odbc/reference/syntax/sqlallochandle-function?view=sql-server-ver15
Useful blog 1:
Useful blog 2:

ODBC access to sql server database is more troublesome. It is not as convenient as using occi to access the oracle database. Bulk operations are not good. For example, to obtain data, after executing sql, you need to cycle to get the data one by one, which is very troublesome, and you need to enter the type of data to be obtained.
Later, it was directly obtained by using the character array type. as follows:

int selectData(const string& sql)
{
    CHAR csql[SQL_MAX_OPTION_STRING_LENGTH] = { 0 };
    strcpy_s(csql, sql.c_str());
    RETCODE ret = SQLExecDirect(hstmt1, (SQLCHAR*)csql, strlen(csql));
    if (ret != SQL_SUCCESS && ret != SQL_SUCCESS_WITH_INFO)
    {
        LLogError("select data error,error code:"<<ret);
        return ret;
    }
    SQLCHAR midData[MAXCHAR] = { 0 };
    SQLLEN midDataLength = 0;
    SQLSMALLINT columnCount = 0;
    SQLNumResultCols(hstmt1,&columnCount);
    int line = 0;
    while (SQLFetch(hstmt1) != SQL_NO_DATA_FOUND)
    {
        // Parameter 1 is the handle of the executed statement,
        // Parameter 2 is the number of columns (in the SQL statement) where the data to be obtained is located,
        // Parameter 3 is the data type, this is more, you need to look at MSDN
        // Parameter 4 is the saved location (address),
        // Parameter 5 is the available position of parameter 4. Since parameter 3 has been set as a long integer, 0 can be used here
        // Parameter 6 is the actual length returned
        stringstream ss;
        ++line;
        ss << line;
        for (int col = 1; col <= columnCount; ++col)
        {
            ret = SQLGetData(hstmt1, col, SQL_C_CHAR, midData, MAXCHAR, &midDataLength);
            if (ret == SQL_SUCCESS || ret == SQL_SUCCESS_WITH_INFO)
            {
                ss << "," << midData;
            }
        }
        //LLogInfo(ss.str());
    }

}

An example of modifying others

This is only for testing and verification. In practice, I encapsulated the class. Otherwise it will be too messy.

#include <windows.h>
#include <sql.h>
#include <sqlext.h>
#include <sqltypes.h>
#include <odbcss.h>
SQLHENV henv = SQL_NULL_HENV;
SQLHDBC hdbc1 = SQL_NULL_HDBC;
SQLHSTMT hstmt1 = SQL_NULL_HSTMT;

/*
    Cpp file function description:
         1. The addition, modification, and deletion in database operations are mainly reflected in SQL statements
         2. Adopt two kinds of direct execution mode and parameter pre-compilation execution mode
*/
int main() {
    return 0;
    RETCODE retcode;
    UCHAR   szDSN[SQL_MAX_DSN_LENGTH + 1] = "dataservice", //odbc database source name, set in odbc data source. After installing sql server manager in windows, the corresponding odbc should also be installed. If not, install one. Then configure an odbc data source (address, account, password, etc.), here is to select which data source to connect to by this data source name.
        szUID[MAXNAME] = "sa",
        szAuthStr[MAXNAME] = "11";
    //SQL statement  
        //Direct SQL statement  
    UCHAR   sql[74] = "SELECT * FROM[DataService].[dbo].[DailyFacts] where stockId = '600036.sh'";// "insert into test values('aaa','100')";
    //Pre-compiled SQL statement  
    UCHAR   pre_sql[29] = "insert into test values(?,?)";
    //1. Connect to the data source  
        //1. Environment handle  
    retcode = SQLAllocHandle(SQL_HANDLE_ENV, NULL, &henv);
    retcode = SQLSetEnvAttr(henv, SQL_ATTR_ODBC_VERSION,
        (SQLPOINTER)SQL_OV_ODBC3,
        SQL_IS_INTEGER);
    //2. Connection handle    
    retcode = SQLAllocHandle(SQL_HANDLE_DBC, henv, &hdbc1);
    retcode = SQLConnect(hdbc1, szDSN, 12, szUID, 2, szAuthStr, 2);
    UCHAR   conInfo[125] = "Provider=SQLOLEDB.1;Persist Security Info=False;User ID=sa;Password=sa;Initial Catalog=DataService;Data Source=10.101.223.13";
    SQLCHAR* pwszConnStr=NULL;
    //retcode = SQLDriverConnect(hdbc1,
    //    GetDesktopWindow(),
    //    pwszConnStr,
    //    SQL_NTS,
    //    NULL,
    //    0,
    //    NULL,
    //    SQL_DRIVER_COMPLETE);


    //Determine whether the connection is successful  
    if ((retcode != SQL_SUCCESS) && (retcode != SQL_SUCCESS_WITH_INFO)) {
        printf("Connection failed!\n");
    }
    else {
        //2. Create and execute one or more SQL statements  
        /*
                 1. Allocate a statement handle
                 2. Create SQL statements
                 3. Execute the statement
                 4. Destroy the statement
        */
        retcode = SQLAllocHandle(SQL_HANDLE_STMT, hdbc1, &hstmt1);
        //The first way  
        //Direct execution  
        //Add operation  
        retcode=SQLExecDirect (hstmt1,sql,74);
        if (retcode != SQL_SUCCESS && retcode != SQL_SUCCESS_WITH_INFO)
        {
            return 0;
        }
        SQLCHAR sqlnID[MAXCHAR] = {0};
        SQLLEN sqlnIDLength = 0;
        SQLCHAR columnName[MAXCHAR] = { 0 };
        SQLSMALLINT DataType= 0;
        SQLSMALLINT NameLength = 0;
        SQLULEN columnsize = 0;
        SQLSMALLINT dd = 0;
        SQLSMALLINT na = 0;
        SQLSMALLINT ddd = 0;
        ///* SQL data type codes */
        //#define SQL_UNKNOWN_TYPE    0
        //#define SQL_CHAR            1
        //#define SQL_NUMERIC         2
        //#define SQL_DECIMAL         3
        //#define SQL_INTEGER         4
        //#define SQL_SMALLINT        5
        //#define SQL_FLOAT           6
        //#define SQL_REAL            7
        //#define SQL_DOUBLE          8
        //#if (ODBCVER >= 0x0300)
        //#define SQL_DATETIME        9
        //#endif
        //#define SQL_VARCHAR         12
        //#if (ODBCVER >= 0x0300)
        //#define SQL_TYPE_DATE       91
        //#define SQL_TYPE_TIME       92
        //#define SQL_TYPE_TIMESTAMP  93
        //#endif
        TIMESTAMP_STRUCT datetime;
        while (SQLFetch(hstmt1) != SQL_NO_DATA_FOUND)
        {
            /* get data */
            SQLGetData(hstmt1, 1, SQL_C_CHAR, sqlnID, MAXCHAR, &sqlnIDLength);
            SQLDescribeCol(hstmt1, 3, columnName, 128, &NameLength, &DataType, &columnsize, &dd, &na);
            SQLGetData(hstmt1, 5, SQL_C_SHORT, &ddd, sizeof(ddd), &sqlnIDLength);
            SQLGetData(hstmt1, 3, SQL_C_TIMESTAMP, &datetime, sizeof(datetime), &sqlnIDLength);
            // Parameter 1 is the handle of the executed statement,
            // Parameter 2 is the number of columns (in the SQL statement) where the data to be obtained is located,
            // Parameter 3 is the data type, this is more, you need to look at MSDN
            // Parameter 4 is the saved location (address),
            // Parameter 5 is the available position of parameter 4. Since parameter 3 has been set as a long integer, 0 can be used here
            // Parameter 6 is the actual length returned
        }

        //The second way  
        //Binding parameters  
        char a[200] = "bbb";
        char b[200] = "200";
        INT64   p = SQL_NTS;
        //1 pre-compiled  
        //SQLPrepare(hstmt1, pre_sql, 29); //The third parameter is the same size as the array, not the database column  
        ////2Bind parameter value  
        //SQLBindParameter(hstmt1, 1, SQL_PARAM_INPUT, SQL_C_CHAR, SQL_CHAR, 200, 0, &a, 0, &p);
        //SQLBindParameter(hstmt1, 2, SQL_PARAM_INPUT, SQL_C_CHAR, SQL_CHAR, 200, 0, &b, 0, &p);
        ////3 execute  
        //SQLExecute(hstmt1);

        printf("Successful operation!");
        //Release the statement handle  
        SQLCloseCursor(hstmt1);
        SQLFreeHandle(SQL_HANDLE_STMT, hstmt1);

    }
    //3. Disconnect the data source  
    /*
           1. Disconnect from the data source.
           2.Release the connection handle.
           3. Release the environment handle (if you no longer need to make more connections in this environment)
    */
    SQLDisconnect(hdbc1);
    SQLFreeHandle(SQL_HANDLE_DBC, hdbc1);
    SQLFreeHandle(SQL_HANDLE_ENV, henv);
    return(0);
}