if not null

In some cases, the SQL statement where condition requires some security judgments, such as if the incoming parameter is empty when the query is in a certain condition, the result of the query is likely to be empty, and maybe we need to find out all

We usually use a strong reference to the object, and if a strong reference exists, the GC does not reclaim the object. Can we keep a reference to the object at the same time and let the GC recycle the object when it's needed? NET provides the

Concurrenthashmap Concurrent ContainerConcurrenthashmap can read data without locking, and its internal structure allows it in the write operation can keep the size of the lock as small as possible, do not have to lock the entire concurrenthashmap.

The data caching system should first be introduced by jQuery1.2, when its event system completes copying de great God's addevent.js, and Addevent has a flaw in implementation, it puts the callback of the event on Eventtarget, which triggers a

Original (C # multithreading and Events): http://www.codeproject.com/Articles/886223/Csharp-Multithreading-and-Events The ' s ' start off with there are no perfectly safe multithreaded event handling as there are caveats/conditions that Mu St be

uilocalnotification There are times when we need to deal with some local push and small details. //judged that he was not active in the foreground before sending the push if ([UIApplication sharedapplication].applicationstate,!=

HashMap is one of the most commonly used data structures to find and delete elements with an O (1) time complexity.This article will use a simple example to explain how the hashmap inside the Scala language works, and look at how get and put work.

Keywords: Oracle numeric function-type date conversion To_char automatic type conversion Date type numeric converter other function numeric functionABS: Find the absolute value function, such as: ABS (−5) 5SQRT: square root function, such as: sqrt (2

From http://blog.sina.com.cn/s/blog_4a5ca024010008tj.html below is the text Xiao Cui's translation of Virgo "Equals method and Hashcode method" (2007-06-22-21:04:42 Cui (folk also called Tri, namely CY, see chat Record series), Hunan people, more

1. HashMap Overview HashMap is an asynchronous implementation of the map interface based on a hash table (Hashtable is similar to HashMap, the only difference being that the method in Hashtalbe is thread-safe, that is, synchronous). This

CREATE tablespace shopping datafile ' D:\oracle\mypc\oradata\orcl\shopping.dbf ' SIZE 20M autoextend on; Create user shopping--creating username identified by shopping-password password character default tablespace shopping--default table space

The CAS algorithm is mentioned several times in this paper, and a simple description of CAs (non-blocking algorithm) is first described. CAS has 3 operands, memory value V, old expected value A, new value B to modify. If and only if the expected

Os.chdir ("dirname") changes the current scripting working directory; the equivalent of a shell CD Os.curdir returns the current directory: ('. ') Os.pardir Gets the parent directory string name of the current directory: ('.. ') Os.makedirs ('

1.IFNULL statement: Ifnull (EXP1, EXP2), return EXP2 if EXP1 is null, return EXP1 if not null The code is as follows Copy Code mysql> SELECT ifnull (null, 100);+-------------------+| Ifnull (NULL, 100) |+---------------

Definitions and usageThe strtotime () function resolves the date-time description of any English text to a Unix timestamp. GrammarStrtotime (time,now) parameter descriptionTime to specify the string to parse.Now is the time stamp used to calculate

The following is my view of some of the procedures in the Pixy record, mainly in order to be able to quickly understand the process of thinking, record down, otherwise so many things light on the brain how to line. There may be flaws in some places,

Recently because of a project, module switching to AJAX request data, when the session failed, after the AJAX request no return value, only the response of the HTML: Now that Ajax is widely used in Web projects, almost everywhere,

Part I Preface Now the most popular web site attack means, to count on the SQL injection, although the SI technology easy to learn to use, and easy to obtain greater access, but because its thunder is too big, now generally a little bit of security

If the users of the MSSQL information is interested, may find master.dbo.sysxlogins inside the user's password, but, password field if not NULL is a bunch of binary can not understand, this password is how to encrypt it? In fact, as long as a

Objective Like C + +, how many bytes are required to define the int type, and how many bytes are required to define the double type, MySQL also controls the data in each column of the table tightly, which is key to the success of the data-driven