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  <=> operator in MySQL


Have you ever seen "<=>" in a SQL query while using MySQL? Does it mean less and equals to and greater than? Actually if you consider it as the union of <= and =>, great, you are close to it. This is one form of equal operator in MySQL, it has the similar meaning to the = operator with some subtle difference. According to MySQL documentation, <=> is NULL-safe equal. This operator performs an equality comparison like the = operator, but returns 1 rather than NULL if both operand...

   MySQL,NULL safe,<=>     2014-03-24 06:23:22


  Why should we keep column as NOT NULL instead of NULL in MySQL?


Keep table column as NOT NULL instead of NULL except in some special cases. This statement is cited by many articles of MySQL optimization, but they don't say why we should do this. Here we discuss about this. First why are there many people using NULL when defining table? The reasons may be: NULL the the default when defining table, the rookies or people who don't want to have much troubles will keep this default setting Many people think NOT NULL will require more space Many people don't want...

   MySQL,NULL,reason     2012-10-27 03:21:27


  A trick of building multithreaded application on Solaris


Firstly, Let’s see a simple multithreaded application: #include <stdio.h> #include <pthread.h> #include <errno.h> void *thread1_func(void *p_arg) { errno = 0; sleep(3); errno = 1; printf("%s exit, errno is %d\n", (char*)p_arg, errno); } void *thread2_func(void *p_arg) { errno = 0; sleep(5); printf("%s exit, errno is %d\n", (char*)p_arg, errno); } int main(void) { pthread_t t1, t2; ...

   C, Solaris     2014-10-14 02:59:40


  Difference between ConcurrentHashMap and Hashtable


Both ConcurrentHashMap and Hashtable are Collection classes for storing key value pairs and they both provide fast element search with a supplied key. They have much in common. However, we will not discuss the similarities between them here, instead we will focus on the differences between them. ConcurrentHashMap and Hashtable are both thread safe. But the mechanism for thread safe is different between them. Hashtable is synchronized, it utilizes the synchronization mechanism; while ConcurrentHa...

   ConcurrentHashMap,Hashtable     2013-11-18 08:06:54


  Undefined property or variable in JavaScript


JavaScript is a weak type language, and also you can use a variable or property where it's undefined. If we don't have correct ways to check whether a property or variable is defined, we may get unexpected results when we try to access the,. How can we check whether a property or variable is undefined? This is actually a somewhat tricky question. Let's start off with some facts about undefined and then see what kind of function is consistent with the ones we care about. JavaScript attaches type...

   Property,Undefined,Array,JavaScript     2014-07-24 06:56:07


  Huawei is open to acquire Nokia


Last night Huawei unveiled a new flagship smartphone Ascend P6 in London. It may be the thinnest smartphone in the world and its potential competitor is Samsung Galaxy S4. Before the press event, an article from FT said that Huawei was open to buy Nokia. "We are considering these sorts of acquisitions,maybe the combination has some synerges but depends on the willingness of Nokia. We are open-minded." remarked by Huawei's Richard Yu. After this news, Nokia's share price surges 11% to $4.10 per ...

   Huawei,Nokia     2013-06-19 00:43:38


  Algorithm : Delete middle node from singly linked list


Questions about singly linked list are frequently asked during technical interviews. Today we will share with you one algorithm question about singly linked list. Here is the problem description. Assuming the only information you are giving is there is a pointer to a middle node of a singly linked list, no other information about the linked list is given. Please delete this node and don't affect the structure of the linked list. Initially you may think this question is easy if you know the hea...

   ALGORITHM,C,LINKED LIST     2015-10-30 05:21:25


  Tips and tricks about JavaScript from Google


JavaScript is now a very popular client side language. It's flexible, powerful but easy to make mistakes. So good programming style is better for you to write efficient and readable JavaScript codes. Here are some tips and tricks about JavaScript from Google. True and False Boolean Expressions The following are all false in boolean expressions: null undefined '' the empty string 0 the number But be careful, because these are all true: '0' the string [] the empty array {}&n...

   JavaScript, Google, Coding standard     2013-02-26 23:11:03


  List of Web Safe Fonts


Here is the list of websafe fonts that I use in my own personal web development. Websafe (or "web safe", "safe for the web") fonts are supposedly fonts that are common among all versions of Windows, Mac, Linux, etc. Fonts that you expect everyone viewing your webpage to have. Please contact me if you know of any other web-safe fonts that should be added to this list. These font names are in typical font-family CSS format, in other words (first choice font), (second choice fon...

   Web,Font,Safe font,Font list,CSS,Font fa     2011-10-01 04:48:03


  Binary tree iterator algorithm


Binary tree pre-order,in-order and post-order traversal are basics in algorithm and data structure.And the recursive binary tree traversal is a classical application of recursion. We define a binary tree node as : // C++ struct Node { int value; Node *left; Node *right; } In order binary tree traversal can be: // C++ void inorder_traverse(Node *node) { if (NULL != node->left) { inorder_traverse(node->left); } do_something(node); if (NULL != node->righ...

   Binary tree,Iterator,Traversal     2013-07-14 21:51:09