count function

Statistical functions ØAVG (expression) function ---- calculate the average value by Column ØSum (expression) function ---- calculate the sum of values by Column Example: average score and total score of students whose student ID is S1 Select AVG

I2C subsystem framework, i2c Subsystem 1 I2C subsystem framework The Linux I2C subsystem consists of the I2C core layer, I2C bus driver, and I2C device driver.   (1) I2C core layer The I2C core provides the registration and cancellation methods for

Replace and regexp usage0 Comments | This entry was posted on Apr 08 2010. Mysql replace usage 1. replace Replace into table (id, name) values ('1', 'A'), ('2', 'bb ') This statement inserts two records into the table. If the primary key id is 1 or 2

First, create a table to describe the problem. Copy codeThe Code is as follows: create table 'result '( 'Name' varchar (20) default NULL, 'Subobject' varchar (20) default NULL, 'Score 'tinyint (4) default NULL ) ENGINE = MyISAM default charset = utf8

+ ------------------------------------------------------------------------------- + | = Read this article for Haohappy | = Notes in the Classes and Objects chapter | = Translation-oriented + personal experiences | = Do not repost it to avoid

Capture warning information and exception information in Perl and write logs This article describes how to capture warning information, exception information, and write logs in Perl, this article provides practical examples of capturing warnings-not

The call, apply, and bind methods in Javascript are described and summarized in detail, applybind The following content is divided into the following sections: 1. Source of the call/apply/bind method 2. Function. prototype. call () 3. Function.

Linux Kernel -- load executable binary files 1. copy_strings, notepad binary copy The last core module exec is analyzed from now on. c. After analyzing this file, it will form a loop with all the previous analyses, from Process Creation, process

2. Introduction to map Map is an associated container. It features that adding or deleting nodes has little impact on the iterator, except that the Operation node has no impact on other nodes. For the iterator, you can modify the real value instead

Close (close the file) Related functions Open, fcntl, shutdown, unlink, fclose Header file # Include Define functions Int close (int fd ); Function Description If the file is no longer needed after

Http://blog.chinaunix.net/u2/82646/showart_1359552.html Open (open a file) Related functions: read, write, fcntl, close, Link, stat, umask, unlink, and fopenHeader file # include # Include # Include Define the int open (const char * pathname, int

the data tables have been created. If we have inserted a lot of data, we can search and display the information in the data table in our favorite way, for example: the entire data table content can be displayed as follows select * from President;

In-depth understanding of the implementation of PHP kernel (6) hash tables and PHP hash tables. In-depth understanding of the implementation of the PHP kernel (6) hash table and the PHP hash table, and in-depth understanding of the original article:

From: http://www.yuanma.org/data/2009/1016/article_3969.htm # Include "stdio. H"# Include "stdlib. H"# Include # Include # Include # Include # Include # Include Using namespace STD; Void main (){Map test; /// It is automatically sorted by the

1. open the file # Include Define the int open (const char * pathname, int flags) function );Int open (const char * pathname, int flags, mode_t mode );Function Description: The pathname parameter points to the file path string to be opened. The

1. Map constructorMap Maphai;Map Maphai;Map mapstring;Map mapstring;mapmapint;mapmapchar;2. Insertion of dataAfter constructing the map container, we can insert data into it. Here are three ways to insert data:First: Insert the pair data with the

Linux Read/write Fread/fwrite The difference between the twoThe 1,fread is buffered and read without buffering.2,fopen is defined in standard C, and open is defined in POSIX.3,fread can read a structure. Read in Linux/unix There is no difference

Basic functions of array manipulationThe key name and value of the arrayArray_values ($arr); Get the value of an arrayArray_keys ($arr); Gets the key name of the arrayArray_flip ($arr); the values in the array are exchanged with the key names (if

Turn from: http://www.cnblogs.com/skynet/archive/2010/12/12/1903949.html has been censored1, how to communicate between processes in the network?The local interprocess communication (IPC) is available in a number of ways, but can be summarized in

Oracle: You can use the NVL (P1,P2) function to replace P1 with P2,However, please note: P1,P2 must be of the same type, can be numeric number, char, date such as Cannot NVL (' Jack ', 5) So, one is char one isSimple and straightforward: NVL (null,0)