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Mysql database sql statement commonly used optimization methods

MySQL database sql statement commonly used optimization methods 1. Query optimization, should try to avoid full table scan, should first consider where and order by the columns involved in the establishment of the index. 2. Should be avoided in the where clause on the field null value judgment, otherwise it will cause the engine to abandon the use of indexes and full table scan, such as: select id from t where num is null You can set the default value of num 0, to ensure that Num column table does not null value ...

XML function library: xml_parser_create

Xml_parser_create the initial XML parser. Syntax: int xml_parser_create (string [encoding]); Return value: integer function kind: Data processing content Description This function is used to initialize a new XML parser. Parameter encoding can be omitted, the character set used for XML, the default value is Iso-8859-1, and other ASCII, UTF-8 two kinds. Success returns PA ...

Automatic hiding when CSS text overflows

CSS tutorial text overflow automatic hiding syntax: overflow:visible | Auto | Hidden | Scroll visible:: Do not cut content nor add scroll bars. If you explicitly declare this default value, the object will be clipped to the size of the window or frame that contains the object. and the Clip property setting will fail. Auto: This is the default value for the Body object and Textrea. Cut content and add scroll bar hidden when needed: Do not show more than objects ...

Sphinx Full-Text Search engine usage guide: sphinx.conf option reference

8.1. Data source configuration option 8.1.1. Type data source types. Must be an option, no default value. Known types include Mysql,pgsql,xmlpipe and xmlpipe2. All other options related to the data source depend on the source type specified by this option. The options associated with SQL data sources (that is, MySQL and PostgreSQL) start with "Sql_", and the options associated with xmlpipe and xmlpipe2 data sources begin with "Xmlpipe_." Example: Ty ...

IE6 below div height display bug collection

IE6 The default font size is roughly between 12-14px, and when you try to define a div that is less than this default value, IE will stubbornly think that the height of this layer should not be less than the row height of the font. So even if you use height:6px; To define the height of a div, the actual display under IE is still a layer of PX left and right. To resolve this problem, you can force the definition of the div's font size, or define the overflow property to restrict the div ...

Nginx Module Reference manual: Geo Module (GEO)

These modules are all compiled into Nginx by default unless a module is manually specified to be excluded in configure. This module creates variables whose values are dependent on the IP address of the client: Geo $geo {default 0; 127.0.0.1/32 2; 192.168.1.0/24 1; 10.1.0.0/16 1;} directive GEO syntax: Geo [$IP _ Variable] $variable {...} default value: None ...

Nginx Module Reference manual: Email authentication module (mail Auth)

Sample configuration: Auth_http localhost:9000/cgi-bin/nginxauth.cgi; Auth_http_timeout 5; Directive auth_http Syntax: auth_http URL Default value: No use field: Mail, server for authentication set URL to Extended http17853.html "> Class Server. Reached protocol please check the Pop3_auth directive in the mail core module ...

Linux compile kernel prompts "Too many open files" solution

The solution that prompts "Too many open files" when Linux compiles the kernel is as follows: This is because the File-max default value (8096) is too small. To resolve this issue, you can execute the following commands (or add them to the Init script under/etc/rcs.d/*) as root: # echo "65536" >/proc/sys/finally enters the unpacked directory and runs the installation command. # CD Vmware-linux-...

Linux Command Encyclopedia disk maintenance: Chsh

Function Description: Replace the shell used when logging on to the system. Syntax: chsh&http://www.aliyun.com/zixun/aggregation/37954.html >nbsp; [-luv] [-S <shell name] [User name] Supplemental NOTE: Each user when logged into the system, will have a preset shell environment, this directive can change its default value. If you do not specify any parameters with the user ...

How to modify the Console (DOS window) background color

The first step is, of course, the brunt. Open the Console (DOS window, Command Prompt window). There are multiple open methods here. The first type of course is to enter CMD in the search box under the Start menu and press ENTER. The second approach is to find the start-Program-attachment-command Prompt in the Start menu. Compare the two types of Windows first. Although the titles of the two windows are different, both of these can execute DOS commands. In the upper left corner of the window, click the left button to pop up a menu, as shown in the picture: In the pop-up menu, we choose "Default value" or "...

PHP program loopholes explain

Several important php.ini options Register Globals php> = 4.2.0, the default value for php.ini's register_globals option is set to Off, and when register_globals is set to On, the program can receive various environment variables from the server , Including the form submitted variables, but also because PHP does not have to initialize the value of the variable, resulting in a big security risk. Example 1: // check_admin () with ...

IRC online instant chat knowledge popular version

IRC is the abbreviation for (Internet Relay Chat) network http://www.aliyun.com/zixun/aggregation/9940.html "> Instant chat." Similar to the common QQ group. But there are some of the users of the perennial in the Linux in the cake hand Oh, QQ group is often they disdain to go in. Oh。 Here's a quick and easy way to get into IRC and ask questions directly: Chatirc ...

Nginx Module Reference Manual: Memcached module (Memcached)

These modules are all compiled into Nginx by default unless a module is manually specified to be excluded in configure. Use this module to simply process caching. Sample configuration: Server {location/{set $memcached _key $uri; Memcached_pass http://www.aliyun.com/zixun/aggregation/11696.html " >name:11211; D ...

Thinkphp 3.1 QuickStart: Variables

In this article we'll learn how to use variables and filter variables in thinkphp. In the webhttp://www.aliyun.com/zixun/aggregation/17799.html "> development process, we often need to obtain system variables or user-submitted data, these variable data is complex, and inadvertently easy to cause security risks, but if the use of good thinkphp provided by the variable access function, you can easily access and control variables. Get variable ...

Nginx Module Reference Manual: Substitution module (substitution)

If you want to use these modules, you must specify the relevant compilation parameters at compile time. This module can be used to search for and replace text in Nginx answers. To use this module, you must specify the following compilation parameters at compile time:--with-http_sub_module option Sample configuration: Location/{sub_filter </head> ' </head>< Script Language= "Javascri ...

Learn 10 basic knowledge of php summary

Learn 10 basic knowledge of PHP Summary Read some of the basics of PHP, I summarize here: 1, embedded in the HTML PHP script there are three ways: The following is quoted content: <script language = "php"> / / embedded Way an echo ("test"); </ script> <? // embedded two echo "<br & g ...

Nginx Module Reference Manual: Map module (MAP)

These modules are all compiled into Nginx by default unless a module is manually specified to be excluded in configure. This module allows you to categorize or simultaneously map multiple values to multiple different values and store them in a variable, and the map instruction is used to create variables, but only when the variable is accepted, the view mapping operation is performed, and the module does not have a performance flaw in processing requests that do not have reference variables. The following example: Map $http _host $name {hostnames; default 0; Example.c ...

Nginx Module Reference manual: HTTP Limit Requests module (http Limit Requests)

These modules are all compiled into Nginx by default unless a module is manually specified to be excluded in configure. This module allows you to limit the number of requests for a specified session or special case. Example configures HTTP {limit_req_zone $binary _remote_addr zone=one:10m rate=1r/s ... location/search/{limit_req zone=o ...

How to use CSS to solve the problem of automatic line wrapping in English words

Prevent form/layer bursting and prevent words from breaking the problem of automatic line wrapping in English words can be said to have tortured many people if a word is written very long, it will break the form, and the tube will be opened in English words. Prevent the form from bursting this problem has been mentioned by a lot of people, later in the earlier version of I also resolved, but caused the English word was broken into line, so the new template does not have to add some CSS code to control this. Today, I found the solution is simple. According to most articles on the Internet, just add in CSS: Code ...

Nginx Series Tutorials: HTTP upstream Request Hash module

Ngx_http_upstream_hash_module This module is provided by a third party and is not included in the Nginx source release version. Upstream_hash This module provides a simple upstream load allocation by hashing a configurable variable (for example, a request URI, an incoming HTTP header, or some combination). Examples of usage are as follows: Upstream backend {: server server1;: Server server2;: Hash $req ...

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