[英]Zend_Db_Select how to select from a subquery (derived table)
如何使用Zend_Db_Select直接從子查詢(派生表)中進行選擇?
看,我有5個具有相同結構的表,我想從中獲取所有行,合並它們並刪除重復項。 我正在使用UNION自動刪除重復項。 問題是我之前為每個表添加了一個靜態列,因此有一個不同的列=> duplicatation發生。
這是我目前的查詢:
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
了解如何將靜態值添加到新列category
? 現在其他一切都是相同的(有重復的行),但由於它們來自不同的類別,因此UNION無法刪除它們。
所以我想我可以從這個子查詢中SELECT
所有行並將它們分組以刪除重復項,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中運行它並且它完美運行..唯一的問題是....
如何使用Zend_Db_Select的花哨功能執行此操作?
提前致謝!
我不確定你是否可以在Zend_Db_Select的from結構中使用嵌套選擇,或者你是否應該這樣做,但另一種解決方案是獲取db適配器並手動構建sql查詢。
$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
");
相關: Zend_Db_Table子查詢
只需定義一個引用子查詢的類,然后您就可以在一個地方添加更多處理:
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(我的情況下,來自實際應用程序的copypaste,工作)或JOIN(推測,沒試過)。
$innerSelect = $dbTableSomeModel->select(true);
// Configure it, maybe kick around many layers of abstarction
$nestedSelect->from(
array(
'derived_alias' => new Acme_Db_Expr_Subquery( $innerSelect ),
)
,array(
'column_alias' => 'column_expression',
)
);
從我從Zend_Db_Select的源代碼中可以看出,它的from()方法調用它的_join()方法,該方法有一個情況,即from()的第一個參數是Zend_Db_Select對象: http://framework.zend。 COM / SVN /框架/標准/主干/庫/的Zend / DB / Select.php
} else if ($name instanceof Zend_Db_Expr|| $name instanceof Zend_Db_Select) {
$tableName = $name;
$correlationName = $this->_uniqueCorrelation('t');
如果沒有,from()應該支持別名子查詢,方法是將它包裝在括號中以強制它轉換為Zend_Db_Expr實例,如本例中的joinRight(): Zend Framework:Zend_Db_Select - 如何連接自定義子查詢表?
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