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AWS SimpleDB 的默认结果限制为 100，我正在尝试从我的数据库中获取最后 20 条记录。他们的在线帮助指出：“count(*) 和 select 返回的下一个标记是可以互换的，只要 where 和 order by 子句匹配即可。例如，如果您想返回前 10,000 项之后的 200 项（类似于偏移量） )，您可以使用 10,000 的限制子句执行计数，并使用下一个标记通过 select 返回接下来的 200 个项目。”

所以我试图弄清楚如何执行这两个操作。我首先计算记录数（在我的示例中约为 160），然后从中减去 20 以创建偏移量。但 AWS 仍在返回前 100 条记录。我认为“//++”之间的代码在创建偏移量时不正确。 

            //++ AWS has display limit of 100 so create offset by starting from count - 20 
        NSString *sdbAppOffset = [NSString stringWithFormat:@"select count(*) from %@ limit %i",sdbAppUse,iDbaseRecordCountOffset];

        SimpleDBSelectRequest *selectOffsetRequest = [[SimpleDBSelectRequest alloc] initWithSelectExpression:sdbAppOffset];
        selectOffsetRequest.consistentRead = YES;

        SimpleDBSelectResponse *selectOffSetResponse = [sdbClient select:selectOffsetRequest];
        //NSLog(@"sdbAppUse count %i",[selectOffSetResponse.items count]);

        //++ 

        NSString *sdbAppUseString = [NSString stringWithFormat:@"select * from %@",sdbAppUse];

        SimpleDBSelectRequest *selectRequest = [[SimpleDBSelectRequest alloc] initWithSelectExpression:sdbAppUseString];
        selectRequest.consistentRead = YES;

        SimpleDBSelectResponse *selectResponse = [sdbClient select:selectRequest];
        NSLog(@"sdbAppUse count %i",[selectResponse.items count]);

        for (int x = 0; x < [selectResponse.items count]; x++) { 

            SimpleDBItem *registerUser = [selectResponse.items objectAtIndex:x];

            for (SimpleDBAttribute *attribute in registerUser.attributes) {
                NSLog(@"trackUsage registerUser |%@|, name |%@|, value |%@|",registerUser.name, attribute.name, attribute.value);

            }
        }
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