exists

笔者前面介绍了quartz 基于内存的环境搭建, 接下来在前面的基础上, 将项目修改为基于jdbc存储的quartz环境. quartz 2.x 共有11张表, 需要事先导入数据库中. quartz 针对常见的数据库均提供了初始化脚本, 位于docs/dbTables目录中. 1. quartz 相关表 quartz 默认表前缀为QRTZ_, quartz 支持修改表前缀. 但是由于quartz默认表名比较长, 因此修改后可能会导致标识符过长的问题. 通常情况下, 我们并不用关注quartz表数据, 更不需要私自操作quartz 表数据. 笔者这里也只介绍几张核心表: QRTZ_TRIGGERS: 存储所有定时任务的信息 QRTZ_SIMPLE_TRIGGERS: 存储SimpleTrigger 触发器的信息 QRTZ_CRON_TRIGGERS: 存储CronTrigger 触发器的信息 QRTZ_JOB_DETAILS: 存储定时任务的相关信息 QRTZ_FIRED_TRIGGERS: 存储已触发的触发器信息 QRTZ_PAUSED_TRIGGER_GRPS: 存储暂停的触发器组信息 QRTZ_BLOB_TRIGGERS: 存储二进制触发器信息 2. 修改项目 2.1 添加数据库驱动依赖 <!-- 数据库驱动 --> < dependency > < groupId >

I've got a fstream my_file("test.txt"), but I don't know if test.txt exists. In case it exists, I would like to know if I can read it, too. How to do that? I use Linux. I would probably go with: ifstream my_file("test.txt"); if (my_file.good()) { // read away } The good method checks if the stream is ready to be read from. You might use Boost.Filesystem . It has a boost::filesystem::exist function. I don't know how about checking read access rights. You could look in Boost.Filesystem too. However likely there will be no other (portable) way than try to actually read the file. What Operating

I have a function defined as myFun <- function(x, y, ...) { # using exists if (exists("z")) { print("exists z!") } # using missing try(if (!missing("z")) { print("z is not missing!") }, silent = TRUE) # using get try(if (get("z")) { print("get z!") }, silent = TRUE) # anotherFun(...) } In this function, I want to check whether user input "z" in the argument list. How can I do that? I tried exists("z") , missing("z") , and get("z") and none of them works. @Sacha Epskamp has a pretty good solution, but it doesn't always work. The case where it fails is if the "z" argument is passed in as NULL...

在C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727下找到生成ASPState的sql:InstallSqlState.sql 放到查询分析器里执行就可以生成了。 具体代码如下： /********************************************************************* InstallSqlState.SQL Installs the tables, and stored procedures necessary for supporting ASP.NET session state. Copyright Microsoft, Inc. All Rights Reserved. *********************************************************************/ SET QUOTED_IDENTIFIER OFF GO SET ANSI_NULLS ON GO PRINT '' PRINT '-----------------------------------------' PRINT 'Starting execution of InstallSqlState.SQL' PRINT '------------------------

touch 判断坐标位置 如touch((500, 600), duration=1) swipe 滑动位置 wait 等待画面出现 exists 判断画面中是否存在某个图片 test 调用输入法，输入一段文字 assert——exists 断言图片存在于当前画面上 assert——exists 断言图签不存在 refresh刷新显示当前启动的apk 输入text内容并点击 input ，可以在手机上输入该内容。 IME Manger切换输入法，默认为yosemite Quick Button 提供unlock解锁 power电源键操作 snapshot 截图操作 snapshot 截图操作 mute静音， volumn_down``音量降低、 `` volumn_up``音量升高 的快捷操作。 来源： https://www.cnblogs.com/cheng10/p/11414069.html

MongoDB 是由C++语言编写的，是一个基于分布式文件存储的开源数据库系统。 在高负载的情况下，添加更多的节点，可以保证服务器性能。 MongoDB 旨在为WEB应用提供可扩展的高性能数据存储解决方案。 MongoDB 将数据存储为一个文档，数据结构由键值(key=>value)对组成。MongoDB 文档类似于 JSON 对象。字段值可以包含其他文档，数组及文档数组。 1.创建连接 import pymongo client = pymongo.MongoClient('mongodb://localhost:27017') #或 #client = pymongo.MongoClient('localhost'，'27017')## 如果设置了权限,注意xxx用户权限要可以cover到后面使用到的数据库# client = pymongo.MongoClient('10.134.80.119', 20000, username='xxx', password='xxx') 2.连接数据库 #操作test数据库db_name = 'test' db = client[db_name] 3.选择要操作的集合(表) collection_set01 = db['set01'] 下面就可以使用collection_set01进行增删改查操作了. 4.增删改查操作 增 ''' ###

I want to test if a variable exists and if it doesn't, create it. Murray The open() & varnum() functions can be used. Non-zero output from varnum() indicates the variable exists. data try; input var1 var2 var3; datalines; 7 2 2 5 5 3 7 2 7 ; data try2; set try; if _n_ = 1 then do; dsid=open('try'); if varnum(dsid,'var4') = 0 then var4 = .; rc=close(dsid); end; drop rc dsid; run; marq data try2; set try; var4 = coalesce(var4,.); run; (assuming var4 is numeric) AndyBeans Assign var4 to itself. The assignment will create the variable if it doesn't exist and leave the contents in place if it does.

I'm using the jquery library to load the content of an html file. Something like this: $("#Main").load("login.html") If the file (in this case 'login.html') does not exist, I would like to detect it so that I can redirect the user to an error page for example. Any ideas how I can detect if the file to load exists or not? redsquare You can use the ajaxComplete event, whis gives you access to the xhr object which you can query the status of the request e.g a status of 404 will mean the file does not exist. More Info in the docs http://docs.jquery.com/Ajax/ajaxComplete#callback Test here http:/

I have two tables that store value as VARCHAR . I'm populating table and I want just insert values in one of tables if they are not exist in other table. Something like: INSERT IF IS EMPTY(SELECT * FROM t1 where v='test') INTO t2 (v) VALUES ('test') How Can I do that? You need to use some type of INSERT...SELECT query. Update (after clarification): For example, here is how to insert a row in t2 if a corresponding row do not already exist in t1 : INSERT INTO t2 (v) SELECT temp.candidate FROM (SELECT 'test' AS candidate) temp LEFT JOIN t1 ON t1.v = temp.candidate WHERE t1.v IS NULL To insert

转自： http://blog.sina.com.cn/s/blog_65dbc6df0100mvfx.html 1.EXISTS基本意思 英语解释就是存在，不过他的意思也差不多，相当于存在量词 'З'。他不返回数据的，当后带带的查询为空值是，返回 “FALSE”，非空则返回 “TRUE”。 就因为 EXISTS 返回的是真值或假值，所以他所带的子查询一般直接用 'select *' 因为给出列名也没多少意义。 其实， EXISTS属于相关子查询，也就是说子查询的条件依赖于外层父查询的查个属性值。比如： select Sname from Student where exists ( select * from SC where Sno=Student.Sno and Cno ='1'); 所说的依赖也就是这一句 “ Sno=Student.Sno”。这里要说明一下，这个查询过程不是一般的自下而上执行，他与外查询依赖，执行的时候是先从父查询中取一个元组，然后根据条件 Sno=Student.Sno 处理内查询，得到结果再进行父查询中取第二个元组，如果反复。 可与 NOT 连用，反意思反过来理解，如： select Sname from Student where not esists ( select * from SC where Sno=Student.Sno and Cno