Notice (8): file_put_contents(): Write of 270 bytes failed with errno=28 No space left on device [CORE/src/Log/Engine/FileLog.php, line 140]

        if (!$mask) {
            file_put_contents($pathname, $message . "\n", FILE_APPEND);

file_put_contents - [internal], line ??
Cake\Log\Engine\FileLog::log() - CORE/src/Log/Engine/FileLog.php, line 140
Cake\Log\Log::write() - CORE/src/Log/Log.php, line 392
Cake\Log\Log::warning() - CORE/src/Log/Log.php, line 477
DebugKit\ToolbarService::isSuspiciouslyProduction() - ROOT/vendor/cakephp/debug_kit/src/ToolbarService.php, line 169
DebugKit\ToolbarService::isEnabled() - ROOT/vendor/cakephp/debug_kit/src/ToolbarService.php, line 105
DebugKit\Plugin::bootstrap() - ROOT/vendor/cakephp/debug_kit/src/Plugin.php, line 48
Cake\Http\BaseApplication::pluginBootstrap() - CORE/src/Http/BaseApplication.php, line 182
Cake\Http\Server::bootstrap() - CORE/src/Http/Server.php, line 111
Cake\Http\Server::run() - CORE/src/Http/Server.php, line 79
[main] - ROOT/webroot/index.php, line 40

Notice (8): SplFileObject::fwrite() [<a href='https://secure.php.net/splfileobject.fwrite'>splfileobject.fwrite</a>]: Write of 5437 bytes failed with errno=28 No space left on device [CORE/src/Cache/Engine/FileEngine.php, line 141]

Code Context

        $success = $this->_File->ftruncate(0) &&
            $this->_File->fwrite($contents) &&
            $this->_File->fflush();

SplFileObject::fwrite() - [internal], line ??
Cake\Cache\Engine\FileEngine::set() - CORE/src/Cache/Engine/FileEngine.php, line 141
Cake\Database\Schema\CachedCollection::describe() - CORE/src/Database/Schema/CachedCollection.php, line 85
Cake\ORM\Table::getSchema() - CORE/src/ORM/Table.php, line 513
Cake\ORM\Query::addDefaultTypes() - CORE/src/ORM/Query.php, line 290
Cake\ORM\Query::__construct() - CORE/src/ORM/Query.php, line 184
Cake\ORM\Table::query() - CORE/src/ORM/Table.php, line 1702
Cake\ORM\Table::find() - CORE/src/ORM/Table.php, line 1263
App\Controller\NewsController::action_() - APP/Controller/NewsController.php, line 6426
App\Controller\NewsController::get_data() - APP/Controller/NewsController.php, line 5701
App\Controller\NewsController::action_cache() - APP/Controller/NewsController.php, line 5625
App\Controller\NewsController::cache_action() - APP/Controller/NewsController.php, line 5281
App\Controller\NewsController::view() - APP/Controller/NewsController.php, line 3436
Cake\Controller\Controller::invokeAction() - CORE/src/Controller/Controller.php, line 539
Cake\Controller\ControllerFactory::handle() - CORE/src/Controller/ControllerFactory.php, line 140
Cake\Controller\ControllerFactory::invoke() - CORE/src/Controller/ControllerFactory.php, line 115
Cake\Http\BaseApplication::handle() - CORE/src/Http/BaseApplication.php, line 317

Notice (8): unserialize() [<a href='https://secure.php.net/function.unserialize'>function.unserialize</a>]: Error at offset 4079 of 4085 bytes [APP/Controller/NewsController.php, line 5571]

Code Context

               {
                      $a=unserialize($line2);
               }

unserialize - [internal], line ??
App\Controller\NewsController::action_cache() - APP/Controller/NewsController.php, line 5571
App\Controller\NewsController::cache_action() - APP/Controller/NewsController.php, line 5281
App\Controller\NewsController::action_() - APP/Controller/NewsController.php, line 6481
App\Controller\NewsController::get_data() - APP/Controller/NewsController.php, line 5701
App\Controller\NewsController::action_cache() - APP/Controller/NewsController.php, line 5625
App\Controller\NewsController::cache_action() - APP/Controller/NewsController.php, line 5281
App\Controller\NewsController::view() - APP/Controller/NewsController.php, line 3436
Cake\Controller\Controller::invokeAction() - CORE/src/Controller/Controller.php, line 539
Cake\Controller\ControllerFactory::handle() - CORE/src/Controller/ControllerFactory.php, line 140
Cake\Controller\ControllerFactory::invoke() - CORE/src/Controller/ControllerFactory.php, line 115
Cake\Http\BaseApplication::handle() - CORE/src/Http/BaseApplication.php, line 317
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 77
Cake\Http\Middleware\CsrfProtectionMiddleware::process() - CORE/src/Http/Middleware/CsrfProtectionMiddleware.php, line 164
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\I18n\Middleware\LocaleSelectorMiddleware::process() - CORE/src/I18n/Middleware/LocaleSelectorMiddleware.php, line 61
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73

Notice (8): SplFileObject::fwrite() [<a href='https://secure.php.net/splfileobject.fwrite'>splfileobject.fwrite</a>]: Write of 822 bytes failed with errno=28 No space left on device [CORE/src/Cache/Engine/FileEngine.php, line 141]

Code Context

        $success = $this->_File->ftruncate(0) &&
            $this->_File->fwrite($contents) &&
            $this->_File->fflush();

SplFileObject::fwrite() - [internal], line ??
Cake\Cache\Engine\FileEngine::set() - CORE/src/Cache/Engine/FileEngine.php, line 141
Cake\Database\Schema\CachedCollection::describe() - CORE/src/Database/Schema/CachedCollection.php, line 85
Cake\ORM\Table::getSchema() - CORE/src/ORM/Table.php, line 513
Cake\ORM\Query::addDefaultTypes() - CORE/src/ORM/Query.php, line 290
Cake\ORM\Query::__construct() - CORE/src/ORM/Query.php, line 184
Cake\ORM\Table::query() - CORE/src/ORM/Table.php, line 1702
Cake\ORM\Table::find() - CORE/src/ORM/Table.php, line 1263
App\Controller\NewsController::action_() - APP/Controller/NewsController.php, line 6539
App\Controller\NewsController::get_data() - APP/Controller/NewsController.php, line 5701
App\Controller\NewsController::action_cache() - APP/Controller/NewsController.php, line 5625
App\Controller\NewsController::cache_action() - APP/Controller/NewsController.php, line 5281
App\Controller\NewsController::view() - APP/Controller/NewsController.php, line 3436
Cake\Controller\Controller::invokeAction() - CORE/src/Controller/Controller.php, line 539
Cake\Controller\ControllerFactory::handle() - CORE/src/Controller/ControllerFactory.php, line 140
Cake\Controller\ControllerFactory::invoke() - CORE/src/Controller/ControllerFactory.php, line 115
Cake\Http\BaseApplication::handle() - CORE/src/Http/BaseApplication.php, line 317

Warning (2): Undefined array key "nsort" [APP/Controller/NewsController.php, line 3613]

Code Context

                
                $nav_url.="<a href='".$website_info[0]["nsort"]["nsort_url"]."'>".$website_info[0]["nsort"]["nsort_name"]."</a>";

App\Controller\NewsController::view() - APP/Controller/NewsController.php, line 3613
Cake\Controller\Controller::invokeAction() - CORE/src/Controller/Controller.php, line 539
Cake\Controller\ControllerFactory::handle() - CORE/src/Controller/ControllerFactory.php, line 140
Cake\Controller\ControllerFactory::invoke() - CORE/src/Controller/ControllerFactory.php, line 115
Cake\Http\BaseApplication::handle() - CORE/src/Http/BaseApplication.php, line 317
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 77
Cake\Http\Middleware\CsrfProtectionMiddleware::process() - CORE/src/Http/Middleware/CsrfProtectionMiddleware.php, line 164
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\I18n\Middleware\LocaleSelectorMiddleware::process() - CORE/src/I18n/Middleware/LocaleSelectorMiddleware.php, line 61
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\Http\Middleware\BodyParserMiddleware::process() - CORE/src/Http/Middleware/BodyParserMiddleware.php, line 157
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\Routing\Middleware\RoutingMiddleware::process() - CORE/src/Routing/Middleware/RoutingMiddleware.php, line 161
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\Routing\Middleware\AssetMiddleware::process() - CORE/src/Routing/Middleware/AssetMiddleware.php, line 77
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\Error\Middleware\ErrorHandlerMiddleware::process() - CORE/src/Error/Middleware/ErrorHandlerMiddleware.php, line 126

Warning (2): Trying to access array offset on value of type null [APP/Controller/NewsController.php, line 3613]

Code Context

                
                $nav_url.="<a href='".$website_info[0]["nsort"]["nsort_url"]."'>".$website_info[0]["nsort"]["nsort_name"]."</a>";

App\Controller\NewsController::view() - APP/Controller/NewsController.php, line 3613
Cake\Controller\Controller::invokeAction() - CORE/src/Controller/Controller.php, line 539
Cake\Controller\ControllerFactory::handle() - CORE/src/Controller/ControllerFactory.php, line 140
Cake\Controller\ControllerFactory::invoke() - CORE/src/Controller/ControllerFactory.php, line 115
Cake\Http\BaseApplication::handle() - CORE/src/Http/BaseApplication.php, line 317
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 77
Cake\Http\Middleware\CsrfProtectionMiddleware::process() - CORE/src/Http/Middleware/CsrfProtectionMiddleware.php, line 164
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\I18n\Middleware\LocaleSelectorMiddleware::process() - CORE/src/I18n/Middleware/LocaleSelectorMiddleware.php, line 61
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\Http\Middleware\BodyParserMiddleware::process() - CORE/src/Http/Middleware/BodyParserMiddleware.php, line 157
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\Routing\Middleware\RoutingMiddleware::process() - CORE/src/Routing/Middleware/RoutingMiddleware.php, line 161
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\Routing\Middleware\AssetMiddleware::process() - CORE/src/Routing/Middleware/AssetMiddleware.php, line 77
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\Error\Middleware\ErrorHandlerMiddleware::process() - CORE/src/Error/Middleware/ErrorHandlerMiddleware.php, line 126

Warning (2): Undefined array key "nsort" [APP/Controller/NewsController.php, line 3613]

Code Context

                
                $nav_url.="<a href='".$website_info[0]["nsort"]["nsort_url"]."'>".$website_info[0]["nsort"]["nsort_name"]."</a>";

App\Controller\NewsController::view() - APP/Controller/NewsController.php, line 3613
Cake\Controller\Controller::invokeAction() - CORE/src/Controller/Controller.php, line 539
Cake\Controller\ControllerFactory::handle() - CORE/src/Controller/ControllerFactory.php, line 140
Cake\Controller\ControllerFactory::invoke() - CORE/src/Controller/ControllerFactory.php, line 115
Cake\Http\BaseApplication::handle() - CORE/src/Http/BaseApplication.php, line 317
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 77
Cake\Http\Middleware\CsrfProtectionMiddleware::process() - CORE/src/Http/Middleware/CsrfProtectionMiddleware.php, line 164
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\I18n\Middleware\LocaleSelectorMiddleware::process() - CORE/src/I18n/Middleware/LocaleSelectorMiddleware.php, line 61
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\Http\Middleware\BodyParserMiddleware::process() - CORE/src/Http/Middleware/BodyParserMiddleware.php, line 157
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\Routing\Middleware\RoutingMiddleware::process() - CORE/src/Routing/Middleware/RoutingMiddleware.php, line 161
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\Routing\Middleware\AssetMiddleware::process() - CORE/src/Routing/Middleware/AssetMiddleware.php, line 77
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\Error\Middleware\ErrorHandlerMiddleware::process() - CORE/src/Error/Middleware/ErrorHandlerMiddleware.php, line 126

Warning (2): Trying to access array offset on value of type null [APP/Controller/NewsController.php, line 3613]

Code Context

                
                $nav_url.="<a href='".$website_info[0]["nsort"]["nsort_url"]."'>".$website_info[0]["nsort"]["nsort_name"]."</a>";

App\Controller\NewsController::view() - APP/Controller/NewsController.php, line 3613
Cake\Controller\Controller::invokeAction() - CORE/src/Controller/Controller.php, line 539
Cake\Controller\ControllerFactory::handle() - CORE/src/Controller/ControllerFactory.php, line 140
Cake\Controller\ControllerFactory::invoke() - CORE/src/Controller/ControllerFactory.php, line 115
Cake\Http\BaseApplication::handle() - CORE/src/Http/BaseApplication.php, line 317
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 77
Cake\Http\Middleware\CsrfProtectionMiddleware::process() - CORE/src/Http/Middleware/CsrfProtectionMiddleware.php, line 164
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\I18n\Middleware\LocaleSelectorMiddleware::process() - CORE/src/I18n/Middleware/LocaleSelectorMiddleware.php, line 61
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\Http\Middleware\BodyParserMiddleware::process() - CORE/src/Http/Middleware/BodyParserMiddleware.php, line 157
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\Routing\Middleware\RoutingMiddleware::process() - CORE/src/Routing/Middleware/RoutingMiddleware.php, line 161
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\Routing\Middleware\AssetMiddleware::process() - CORE/src/Routing/Middleware/AssetMiddleware.php, line 77
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\Error\Middleware\ErrorHandlerMiddleware::process() - CORE/src/Error/Middleware/ErrorHandlerMiddleware.php, line 126

Sql学习第一天——SQLUNION和UNIONALL操作符认识

Warning (2): Undefined array key "nsort" [ROOT/plugins/Kuhuang/templates/Websites/view.php, line 430]

Code Context

          <div class="info"> 
            <span><a href="<?php echo $website_info[0]["nsort"]["nsort_url"];?>"><i class="fa fa-columns"></i><?php echo $website_info[0]["nsort"]["nsort_name"];?></a></span> 
            <span><i class="fa fa-clock-o"></i><?php echo $website_info[0]["submission_date"];?></span>

include - ROOT/plugins/Kuhuang/templates/Websites/view.php, line 430
Cake\View\View::_evaluate() - CORE/src/View/View.php, line 1184
Cake\View\View::_render() - CORE/src/View/View.php, line 1138
Cake\View\View::render() - CORE/src/View/View.php, line 769
Cake\Controller\Controller::render() - CORE/src/Controller/Controller.php, line 762
App\Controller\NewsController::view() - APP/Controller/NewsController.php, line 3938
Cake\Controller\Controller::invokeAction() - CORE/src/Controller/Controller.php, line 539
Cake\Controller\ControllerFactory::handle() - CORE/src/Controller/ControllerFactory.php, line 140
Cake\Controller\ControllerFactory::invoke() - CORE/src/Controller/ControllerFactory.php, line 115
Cake\Http\BaseApplication::handle() - CORE/src/Http/BaseApplication.php, line 317
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 77
Cake\Http\Middleware\CsrfProtectionMiddleware::process() - CORE/src/Http/Middleware/CsrfProtectionMiddleware.php, line 164
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\I18n\Middleware\LocaleSelectorMiddleware::process() - CORE/src/I18n/Middleware/LocaleSelectorMiddleware.php, line 61
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\Http\Middleware\BodyParserMiddleware::process() - CORE/src/Http/Middleware/BodyParserMiddleware.php, line 157
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73

Notice: file_put_contents() [function.file-put-contents]: Write of 2421 bytes failed with errno=28 No space left on device in /www/wwwroot/www.adminso.com/vendor/cakephp/cakephp/src/Log/Engine/FileLog.php on line 140

Warning (2): Trying to access array offset on value of type null [ROOT/plugins/Kuhuang/templates/Websites/view.php, line 430]Code Context          <div class="info"> 
            <span><a href="<?php echo $website_info[0]["nsort"]["nsort_url"];?>"><i class="fa fa-columns"></i><?php echo $website_info[0]["nsort"]["nsort_name"];?></a></span> 
            <span><i class="fa fa-clock-o"></i><?php echo $website_info[0]["submission_date"];?></span> 
include - ROOT/plugins/Kuhuang/templates/Websites/view.php, line 430
Cake\View\View::_evaluate() - CORE/src/View/View.php, line 1184
Cake\View\View::_render() - CORE/src/View/View.php, line 1138
Cake\View\View::render() - CORE/src/View/View.php, line 769
Cake\Controller\Controller::render() - CORE/src/Controller/Controller.php, line 762
App\Controller\NewsController::view() - APP/Controller/NewsController.php, line 3938
Cake\Controller\Controller::invokeAction() - CORE/src/Controller/Controller.php, line 539
Cake\Controller\ControllerFactory::handle() - CORE/src/Controller/ControllerFactory.php, line 140
Cake\Controller\ControllerFactory::invoke() - CORE/src/Controller/ControllerFactory.php, line 115
Cake\Http\BaseApplication::handle() - CORE/src/Http/BaseApplication.php, line 317
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 77
Cake\Http\Middleware\CsrfProtectionMiddleware::process() - CORE/src/Http/Middleware/CsrfProtectionMiddleware.php, line 164
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\I18n\Middleware\LocaleSelectorMiddleware::process() - CORE/src/I18n/Middleware/LocaleSelectorMiddleware.php, line 61
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\Http\Middleware\BodyParserMiddleware::process() - CORE/src/Http/Middleware/BodyParserMiddleware.php, line 157
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73

Notice: file_put_contents() [function.file-put-contents]: Write of 2445 bytes failed with errno=28 No space left on device in /www/wwwroot/www.adminso.com/vendor/cakephp/cakephp/src/Log/Engine/FileLog.php on line 140
">

Warning (2): Undefined array key "nsort" [ROOT/plugins/Kuhuang/templates/Websites/view.php, line 430]Code Context          <div class="info"> 
            <span><a href="<?php echo $website_info[0]["nsort"]["nsort_url"];?>"><i class="fa fa-columns"></i><?php echo $website_info[0]["nsort"]["nsort_name"];?></a></span> 
            <span><i class="fa fa-clock-o"></i><?php echo $website_info[0]["submission_date"];?></span> 
include - ROOT/plugins/Kuhuang/templates/Websites/view.php, line 430
Cake\View\View::_evaluate() - CORE/src/View/View.php, line 1184
Cake\View\View::_render() - CORE/src/View/View.php, line 1138
Cake\View\View::render() - CORE/src/View/View.php, line 769
Cake\Controller\Controller::render() - CORE/src/Controller/Controller.php, line 762
App\Controller\NewsController::view() - APP/Controller/NewsController.php, line 3938
Cake\Controller\Controller::invokeAction() - CORE/src/Controller/Controller.php, line 539
Cake\Controller\ControllerFactory::handle() - CORE/src/Controller/ControllerFactory.php, line 140
Cake\Controller\ControllerFactory::invoke() - CORE/src/Controller/ControllerFactory.php, line 115
Cake\Http\BaseApplication::handle() - CORE/src/Http/BaseApplication.php, line 317
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 77
Cake\Http\Middleware\CsrfProtectionMiddleware::process() - CORE/src/Http/Middleware/CsrfProtectionMiddleware.php, line 164
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\I18n\Middleware\LocaleSelectorMiddleware::process() - CORE/src/I18n/Middleware/LocaleSelectorMiddleware.php, line 61
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\Http\Middleware\BodyParserMiddleware::process() - CORE/src/Http/Middleware/BodyParserMiddleware.php, line 157
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73

Warning (2): Trying to access array offset on value of type null [ROOT/plugins/Kuhuang/templates/Websites/view.php, line 430]Code Context          <div class="info"> 
            <span><a href="<?php echo $website_info[0]["nsort"]["nsort_url"];?>"><i class="fa fa-columns"></i><?php echo $website_info[0]["nsort"]["nsort_name"];?></a></span> 
            <span><i class="fa fa-clock-o"></i><?php echo $website_info[0]["submission_date"];?></span> 
include - ROOT/plugins/Kuhuang/templates/Websites/view.php, line 430
Cake\View\View::_evaluate() - CORE/src/View/View.php, line 1184
Cake\View\View::_render() - CORE/src/View/View.php, line 1138
Cake\View\View::render() - CORE/src/View/View.php, line 769
Cake\Controller\Controller::render() - CORE/src/Controller/Controller.php, line 762
App\Controller\NewsController::view() - APP/Controller/NewsController.php, line 3938
Cake\Controller\Controller::invokeAction() - CORE/src/Controller/Controller.php, line 539
Cake\Controller\ControllerFactory::handle() - CORE/src/Controller/ControllerFactory.php, line 140
Cake\Controller\ControllerFactory::invoke() - CORE/src/Controller/ControllerFactory.php, line 115
Cake\Http\BaseApplication::handle() - CORE/src/Http/BaseApplication.php, line 317
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 77
Cake\Http\Middleware\CsrfProtectionMiddleware::process() - CORE/src/Http/Middleware/CsrfProtectionMiddleware.php, line 164
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\I18n\Middleware\LocaleSelectorMiddleware::process() - CORE/src/I18n/Middleware/LocaleSelectorMiddleware.php, line 61
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73
Cake\Http\Middleware\BodyParserMiddleware::process() - CORE/src/Http/Middleware/BodyParserMiddleware.php, line 157
Cake\Http\Runner::handle() - CORE/src/Http/Runner.php, line 73

关于SQLUNION操作符UNION操作符用于合并两个或多个SELECT语句的结果集。注意：1.UNION内部的SELECT语句必须拥有相同数量的列

关于SQL UNION 操作符
UNION 操作符用于合并两个或多个 SELECT 语句的结果集。
注意：
1.UNION 内部的 SELECT 语句必须拥有相同数量的列。列也必须拥有相似的数据类型。同时，每条 SELECT 语句中的列的顺序必须相同。
2.UNION 结果集中的列名总是等于 UNION 中第一个 SELECT 语句中的列名。
SQL UNION 语法（结果集没有重复值）：

复制代码代码如下:

 
SELECT s FROM table1 
UNION 
SELECT s FROM table2 

SQL UNION ALL 语法（结果集有重复的值）：

复制代码代码如下:

 
SELECT s FROM table1 
UNION ALL 
SELECT s FROM table2 

例子表：
　表一（Employees_China）：
　　　　E_ID E_Name
　　　　01　　　　Zhang, Hua
　　　　02　　　　Wang, Wei
　　　　03　　　　Carter, Thomas
　　　　04　　　　Yang, Ming
　表二（Employees_USA）：
　　　　E_ID　　 E_Name
　　　　01　　　　Adams, John
　　　　02　　　　Bush, George
　　　　03　　　　Carter, Thomas
　　　　04　　　　Gates, Bill
实例：
关于UNION：　

复制代码代码如下:

　 
SELECT E_Name FROM Employees_China 
　　UNION 
　　SELECT E_Name FROM Employees_USA 

结果如下(去除了重复数据)：

E_Name
Zhang, Hua
Wang, Wei
Carter, Thomas
Yang, Ming
Adams, John
Bush, George
Gates, Bill

关于UNION ALL：

复制代码代码如下:

 
　　SELECT E_Name FROM Employees_China 　　 
　　UNION ALL 

　　SELECT E_Name FROM Employees_USA 

　结果如下（还保留了重复的数据）：

E_Name
Zhang, Hua
Wang, Wei
Carter, Thomas
Yang, Ming
Adams, John
Bush, George
Carter, Thomas
Gates, Bill

标签: Sql 学习第一天 SQLUNION UNIONALL 操作认识

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Sql学习第一天——SQLUNION和UNIONALL操作符认识

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Sql学习第一天——SQLUNION和UNIONALL操作符认识

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