不用讨论，手册上写得很清楚。 mysql_use_result() initiates a result set retrieval but does not actually read the result set into the client like mysql_store_result() does. Instead, each row must be retrieved individually by making calls to mysql_fetch_row(). This reads the result of a query directly from the server without storing it in a temporary table or local buffer, which is somewhat faster and uses much less memory than mysql_store_result(). The client allocates memory only for the current row and a communication buffer that may grow up to max_allowed_packet bytes. On the other hand, you shouldn't use mysql_use_result() if you are doing a lot of processing for each row on the client side, or if the output is sent to a screen on which the user may type a ^S (stop scroll). This ties up the server and prevent other threads from updating any tables from which the data is being fetched. When using mysql_use_result(), you must execute mysql_fetch_row() until a NULL value is returned, otherwise, the unfetched rows are returned as part of the result set for your next query. The C API gives the error Commands out of sync; you can't run this command now if you forget to do this!
调用端的内存指的是mysql服务器的内存吗？但是我做实验测试了一下，返回一个大约64M的结果集，mysql内存只涨了几兆。这是为什么呢？
汗！大哥，去吧mysql手册看清楚，msyql_stroe_reslut才是返回到调用端的内存。
mysql_use_result() initiates a result set retrieval but does not actually read the result set into the client like mysql_store_result() does. Instead, each row must be retrieved individually by making calls to mysql_fetch_row(). This reads the result of a query directly from the server without storing it in a temporary table or local buffer, which is somewhat faster and uses much less memory than mysql_store_result(). The client allocates memory only for the current row and a communication buffer that may grow up to max_allowed_packet bytes. On the other hand, you shouldn't use mysql_use_result() if you are doing a lot of processing for each row on the client side, or if the output is sent to a screen on which the user may type a ^S (stop scroll). This ties up the server and prevent other threads from updating any tables from which the data is being fetched. When using mysql_use_result(), you must execute mysql_fetch_row() until a NULL value is returned, otherwise, the unfetched rows are returned as part of the result set for your next query. The C API gives the error Commands out of sync; you can't run this command now if you forget to do this!
毫无疑问，他们最终都是把结果放到客户端内存的
只不过mysql_use_reslut是通过mysql_fetch_row，把记录一条一条读过来的，消耗的内存较少。
手册上面只是说了客户端的情况，我现在想知道，在mysql_use_result()查询语句返回结果集时，整个结果集在mysql端做了什么？我做了一个测试，大致如下：
线程1做查询：select * from tab;
在mysql_use_result()返回结果集后， mysql_fetch_row之前，另外开一个线程2，对tab表进行更新：update tab set col1 = 'new' where col1 = 'old';更新后，表的数据变化了
此时线程1执行 mysql_fetch_row，发现返回的结果是更新前的内容，即：col1 = 'old'
实验表名，mysql_use_result()的整个结果集被缓存。我想问的是：此结果集缓存在哪了？是mysql内存吗？但是mysql服务器并没有增涨那么多的内存啊？