经过不断摸索，我发现直接调用mysql C API更好，出了错也容易把握。以下是部分代码，贴出来给大家参考参考

本文介绍了一种通过MySQL C API直接连接和查询数据库的方法，展示了如何设置连接参数，处理字符集，并根据条件构造SQL语句。示例代码中包含从不同数据源获取股票历史记录的实现，涉及字符串编码转换和数据解析。
摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >
-(NSInteger)getHistoryRecordwithStockID:(NSString*)stockID LeaderName:(NSString*)leaderName dataSource:(NSInteger)dataSource{
    
    ////////////using MySQL C API 
    MYSQL *conn;
    MYSQL_RES *res;
    MYSQL_ROW row;
    
    char *server = "localhost";
    char *user = "root";
    char *password = "123456"; 
    char *database = "stockinfo";
    
    conn = mysql_init(NULL);

    
    if (!mysql_real_connect(conn, server,
                            user, password, database, 0, NULL, 0)) {
        fprintf(stderr, "%s\n", mysql_error(conn));
        exit(1);
    }
    if (!mysql_set_character_set(conn, "gbk")) 
    {
        printf("New client character set: %s\\n", mysql_character_set_name(conn));        
    }

    if (dataSourceType==ShangeHaiMainBoard) {
        tableName=@"shzb";
    }else if (dataSourceType==ShenzhenMainBoard) {
        tableName=@"szzb";
    }else if (dataSourceType==ShenzhenSmallBoard) {
        tableName=@"szzxb";
    }else if (dataSourceType==HongKongMainBoard) {
        tableName=@"hkzb";
    }

    NSString  *queryString=[NSString stringWithFormat: @"SELECT * FROM %@ ",tableName];
    NSString  *newQueryString=NULL;

    
    if (!(stockID==nil||[stockID isEqualToString:@""])&& ([leaderName  isEqualToString: @""]||leaderName==nil)) {
        newQueryString=[queryString stringByAppendingFormat:@"WHERE companyID like '%@'",stockID];
    }
    else if ( (stockID==nil||[stockID isEqualToString:@""])&& !([leaderName  isEqualToString: @""]||leaderName==nil)){
        newQueryString=[queryString stringByAppendingFormat:@"WHERE holdingChangerName like '%@'",leaderName];
    }else if  ( !(stockID==nil) && !(leaderName==nil)){
        newQueryString=[queryString stringByAppendingFormat:@"WHERE holdingChangerName like '%@' AND companyID like '%@'",leaderName,stockID];
    }

    NSStringEncoding  enc=CFStringConvertEncodingToNSStringEncoding(kCFStringEncodingGB_18030_2000 );   //转换编码，包括中文                            

    if (mysql_query(conn, (char*)[newQueryString cStringUsingEncoding:enc])) {
        fprintf(stderr, "%s\n", mysql_error(conn));
        exit(1);
    }
    res = mysql_store_result(conn);
    
    [historyRecords removeAllObjects];
    int rowCount = mysql_num_rows(res);
    NSLog(@"rowCount:%d",rowCount);

    for(int i = 0; i < rowCount; i++)
    {
        StockInfo  *stockinfo= [[StockInfo alloc]init];
        if(row = mysql_fetch_row(res))
        {    
            if ([dataSource isEqualToString: @"shzb"]) {
                stockinfo.companyID=[NSString stringWithUTF8String:row[0]];
                stockinfo.companyName=[NSString stringWithCString:row[1]encoding:enc ];
                stockinfo.leaderName=[NSString stringWithCString:row[2]encoding:enc ];
                stockinfo.holdingChangerName=[NSString stringWithCString:row[3]encoding:enc ];   //股份变更者与董监高为同一人
                stockinfo.job=[NSString stringWithUTF8String:row[4]];
                stockinfo.stockType=[NSString stringWithUTF8String:row[5]];
                stockinfo.currencyType=[NSString stringWithUTF8String:row[6]];
                stockinfo.numberOfSharesBeforeChange=[[[NSString stringWithUTF8String:row[7]]stringByReplacingOccurrencesOfString:@"," withString:@""]floatValue];
                stockinfo.numberOfSharesChanged=[[[NSString stringWithUTF8String:row[8]]stringByReplacingOccurrencesOfString:@"," withString:@""]floatValue];
                stockinfo.averagePrice=[[NSString stringWithUTF8String:row[9]]floatValue];
                stockinfo.numberOfSharesAfterChange=[[[NSString stringWithUTF8String:row[10]]stringByReplacingOccurrencesOfString:@"," withString:@""]floatValue];
                stockinfo.changeReason=[NSString stringWithUTF8String:row[11]];
                stockinfo.changeDate=[StockInfo dateFromString:[NSString stringWithUTF8String:row[12]] withFormat:@"yyyy-MM-dd"];
                stockinfo.reportedDate=[StockInfo dateFromString:[NSString stringWithUTF8String:row[13]] withFormat:@"yyyy-MM-dd"];                
            }
            else if([dataSource isEqualToString:@"szzb"]||[dataSource isEqualToString:@"szzxb"]){
                stockinfo.companyID=[NSString stringWithUTF8String:row[0]];
                stockinfo.companyName=[NSString stringWithCString:row[1]encoding:enc ];
                stockinfo.holdingChangerName=[NSString stringWithCString:row[2]encoding:enc ];
                stockinfo.changeDate=[StockInfo dateFromString:[NSString stringWithUTF8String:row[3]] withFormat:@"yyyy-MM-dd"];
                stockinfo.numberOfSharesChanged=[[[NSString stringWithUTF8String:row[4]]stringByReplacingOccurrencesOfString:@"," withString:@""] floatValue];
                stockinfo.averagePrice=[[NSString stringWithUTF8String:row[5]]floatValue];
                stockinfo.changeReason=[NSString stringWithUTF8String:row[6]];
                stockinfo.holdingRateChanged=[[NSString stringWithUTF8String:row[7] ]floatValue];
                stockinfo.numberOfSharesAfterChange=[[[NSString stringWithUTF8String:row[8]]stringByReplacingOccurrencesOfString:@"," withString:@""]floatValue];
                stockinfo.leaderName=[NSString stringWithCString:row[9]encoding:enc];
                stockinfo.job=[NSString stringWithUTF8String:row[10]];
                
            }else if ([dataSource isEqualToString:@"hkzb"]||[dataSource isEqualToString:@"hkcyb"]) {
                stockinfo.companyID=[NSString stringWithUTF8String:row[0]];
                stockinfo.companyName=[NSString stringWithCString:row[1]encoding:enc ];
                stockinfo.holdingChangerName=[NSString stringWithCString:row[2]encoding:enc ];
                stockinfo.numberOfSharesChanged=[[[NSString stringWithUTF8String:row[3]]stringByReplacingOccurrencesOfString:@"," withString:@""] floatValue];
                stockinfo.numberOfSharesAfterChange=[[[NSString stringWithUTF8String:row[4]]stringByReplacingOccurrencesOfString:@"," withString:@""]floatValue];
                stockinfo.holdingRateAfterChange=[[NSString stringWithUTF8String:row[5]]floatValue];
                NSLog(@"changedate:%@",[NSString stringWithCString:row[6]encoding:enc] );
                stockinfo.changeDate=[StockInfo dateFromString:[NSString stringWithCString:row[6]encoding:enc ] withFormat:@"yyyy-MM-dd"];                
            }
            
        }
        row = NULL;
        
        [historyRecords addObject:stockinfo];
        [stockinfo release];
    }    
    
    
    
    mysql_free_result(res);
    mysql_close(conn);
    
    [self.table reloadData];
    return rowCount;
}