[英]Zend_Db_Select how to select from a subquery (derived table)
如何使用Zend_Db_Select直接从子查询(派生表)中进行选择?
看,我有5个具有相同结构的表,我想从中获取所有行,合并它们并删除重复项。 我正在使用UNION自动删除重复项。 问题是我之前为每个表添加了一个静态列,因此有一个不同的列=> duplicatation发生。
这是我目前的查询:
SELECT `news_main`.*, 'main' as `category`
FROM `news_main`
UNION SELECT `news_politics`.*, 'politics' as `category` FROM `news_politics`
UNION SELECT `news_society`.*, 'society' as `category` FROM `news_society`
UNION SELECT `news_world`.*, 'world' as `category` FROM `news_world`
UNION SELECT `news_business`.*, 'business' as `category` FROM `news_business`
ORDER BY `date` DESC LIMIT 8
了解如何将静态值添加到新列category
? 现在其他一切都是相同的(有重复的行),但由于它们来自不同的类别,因此UNION无法删除它们。
所以我想我可以从这个子查询中SELECT
所有行并将它们分组以删除重复项,如下所示:
SELECT *
FROM (
SELECT `news_main`.*, 'main' as `category`
FROM `news_main`
UNION SELECT `news_politics`.*, 'politics' as `category` FROM `news_politics`
UNION SELECT `news_society`.*, 'society' as `category` FROM `news_society`
UNION SELECT `news_world`.*, 'world' as `category` FROM `news_world`
UNION SELECT `news_business`.*, 'business' as `category` FROM `news_business`
ORDER BY `date` DESC LIMIT 8
) as subtable
GROUP BY `source`
ORDER BY `date` DESC
我在MySQL中运行它并且它完美运行..唯一的问题是....
如何使用Zend_Db_Select的花哨功能执行此操作?
提前致谢!
我不确定你是否可以在Zend_Db_Select的from结构中使用嵌套选择,或者你是否应该这样做,但另一种解决方案是获取db适配器并手动构建sql查询。
$db = Zend_Db_Table::getDefaultAdapter();
$db->query("SELECT *
FROM (
SELECT `news_main`.*, 'main' as `category`
FROM `news_main`
UNION SELECT `news_politics`.*, 'politics' as `category` FROM `news_politics`
UNION SELECT `news_society`.*, 'society' as `category` FROM `news_society`
UNION SELECT `news_world`.*, 'world' as `category` FROM `news_world`
UNION SELECT `news_business`.*, 'business' as `category` FROM `news_business`
ORDER BY `date` DESC LIMIT 8
) as subtable
GROUP BY `source`
ORDER BY `date` DESC
");
相关: Zend_Db_Table子查询
只需定义一个引用子查询的类,然后您就可以在一个地方添加更多处理:
class Acme_Db_Expr_Subquery extends Zend_Db_Expr {
public function __toString()
{
return '( ' . $this->_expression . ' )';
}
}
然后在FROM子句中使用它(我的情况下,来自实际应用程序的copypaste,工作)或JOIN(推测,没试过)。
$innerSelect = $dbTableSomeModel->select(true);
// Configure it, maybe kick around many layers of abstarction
$nestedSelect->from(
array(
'derived_alias' => new Acme_Db_Expr_Subquery( $innerSelect ),
)
,array(
'column_alias' => 'column_expression',
)
);
从我从Zend_Db_Select的源代码中可以看出,它的from()方法调用它的_join()方法,该方法有一个情况,即from()的第一个参数是Zend_Db_Select对象: http://framework.zend。 COM / SVN /框架/标准/主干/库/的Zend / DB / Select.php
} else if ($name instanceof Zend_Db_Expr|| $name instanceof Zend_Db_Select) {
$tableName = $name;
$correlationName = $this->_uniqueCorrelation('t');
如果没有,from()应该支持别名子查询,方法是将它包装在括号中以强制它转换为Zend_Db_Expr实例,如本例中的joinRight(): Zend Framework:Zend_Db_Select - 如何连接自定义子查询表?
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