select

问题 I have a problem in Oracle SQL that I'm trying to get my head around. I'll illustrate with an example. I have three tables that I am querying: Employees __________________________________________ | EmployeeID | Name | | 1 | John Smith | | 2 | Douglas Hoppalot | | 3 | Harry Holiday | ... InternalCosts ________________________________ | IntID | Amount | EmployeeID | | 1 | 10 | 1 | | 2 | 20 | 2 | | 3 | 30 | 1 | ... ExternalCosts ________________________________ | ExtID | Amount | EmployeeID | |

问题 I was only able to set maximum of 20 seconds as the timeout parameter in select () API. Whatever value i gave above 20, select() is returning after 20 seconds itself... So i was trying to write a loop for the timeout of 1 minute like this int timeoutcount = 0; do { FD_ZERO(&fd); FD_SET(sock,&fd); timeout.tv_sec = 20; timeout.tv_usec = 0; rc = select (sock+1,&fd,null,null,&timeout); if(rc ==0) timeoutcount += 20; } while(rc ==0 && timeoutcount <60) please help me out...am i going in the

问题 I was only able to set maximum of 20 seconds as the timeout parameter in select () API. Whatever value i gave above 20, select() is returning after 20 seconds itself... So i was trying to write a loop for the timeout of 1 minute like this int timeoutcount = 0; do { FD_ZERO(&fd); FD_SET(sock,&fd); timeout.tv_sec = 20; timeout.tv_usec = 0; rc = select (sock+1,&fd,null,null,&timeout); if(rc ==0) timeoutcount += 20; } while(rc ==0 && timeoutcount <60) please help me out...am i going in the

问题 I was only able to set maximum of 20 seconds as the timeout parameter in select () API. Whatever value i gave above 20, select() is returning after 20 seconds itself... So i was trying to write a loop for the timeout of 1 minute like this int timeoutcount = 0; do { FD_ZERO(&fd); FD_SET(sock,&fd); timeout.tv_sec = 20; timeout.tv_usec = 0; rc = select (sock+1,&fd,null,null,&timeout); if(rc ==0) timeoutcount += 20; } while(rc ==0 && timeoutcount <60) please help me out...am i going in the

问题 I was only able to set maximum of 20 seconds as the timeout parameter in select () API. Whatever value i gave above 20, select() is returning after 20 seconds itself... So i was trying to write a loop for the timeout of 1 minute like this int timeoutcount = 0; do { FD_ZERO(&fd); FD_SET(sock,&fd); timeout.tv_sec = 20; timeout.tv_usec = 0; rc = select (sock+1,&fd,null,null,&timeout); if(rc ==0) timeoutcount += 20; } while(rc ==0 && timeoutcount <60) please help me out...am i going in the

问题 i am start using this 2 hibernate annotations in my APP. @DynamicUpdate(value=true) @SelectBeforeUpdate(value=true) first i will try to explain what i understand about it to know if i am right about it. @DynamicUpdate(value=true) updates only the modified values in the entity Hibernate needs to track those changes @SelectBeforeUpdate(value=true) creates a select before update to know which properties has been changed this is useful when the entity has been loaded and updated on different

问题 I would like to select one element from a list using python following the normal distribution. I have a list, e.g., alist = ['an', 'am', 'apple', 'cool', 'why'] For example, according to the probability density function (PDF) of normal distribution, the 3rd element in the given list should have the largest probability to be chosen.Any suggestions? 回答1: from random import normalvariate def normal_choice(lst, mean=None, stddev=None): if mean is None: # if mean is not specified, use center of

问题 I'm having a little trouble with sockets, when looping I'm not receiving data except for the first loop, it's timing out each time. If I close and reopen the socket each loop though I seem to be getting the data correctly. Any ideas as to why? Example of looping without closing: int socketHandle = socket(AF_INET,SOCK_DGRAM,0); sockaddr_in serverAddr; serverAddr.sin_family = AF_INET; serverAddr.sin_addr.s_addr = inet_addr(/*UDP IP ADDRESS*/); serverAddr.sin_port = htons(/*UDP PORT*/); struct

问题 I'm having a little trouble with sockets, when looping I'm not receiving data except for the first loop, it's timing out each time. If I close and reopen the socket each loop though I seem to be getting the data correctly. Any ideas as to why? Example of looping without closing: int socketHandle = socket(AF_INET,SOCK_DGRAM,0); sockaddr_in serverAddr; serverAddr.sin_family = AF_INET; serverAddr.sin_addr.s_addr = inet_addr(/*UDP IP ADDRESS*/); serverAddr.sin_port = htons(/*UDP PORT*/); struct

问题 Is it right to expect that, for the typical modern RDBMS, querying by one specific primary key is as fast as querying a hashtable by key? Or is there "actual work" done to traverse the table and track down the primary key value? That seems unthinkably wasteful, even if there are automatic indexes for primary keys. 回答1: Database operation involves access of secondary memory unit (Disk). And to achieve efficiency important is to reduce block access time(not operations). Complexity of Select