當使用工會佔位符似乎從初始值在工會

Question

選擇用於替換這或多或少與此相關的How to preserve the order of the fields to be selected when using $query->addExpression()

我在做什麼正在對多個表union。但我也需要知道來自哪個表的值。所以我只是添加如下內容：$query->addExpression(':table', 'table_name', array(':table' => $table_name));

問題是，只要您創建聯合表名將被第一個查詢替換。

檢查下面的例子：

$table_name = 'table_one'; 
$query_1 = db_select('table_one', 't1'); 
$query_1->fields('t1', array('field_1', 'field_2')); 
$query_1->addExpression(':table', 'table_name', array(':table' => $table_name)); 

$table_name = 'table_two'; 
$query_2 = db_select('table_two', 't2'); 
$query_2->fields('t2', array('field_1', 'field_2')); 
$query_2->addExpression(':table', 'table_name', array(':table' => $table_name));  

$table_name = 'table_three'; 
$query_3 = db_select('table_three', 't3'); 
$query_3->fields('t3', array('field_1', 'field_2')); 
$query_3->addExpression(':table', 'table_name', array(':table' => $table_name)); 

如果我們檢查選擇單獨看起來都很好，你會得到預期的結果，但使用時，工會你只會看到table_one所有的地方。

// dpq($query_1) - OK 
SELECT t1.field_1 AS field_1, t1.field_2 AS field_2, 'table_one' AS table_name 
FROM 
{table_one} t1 

// dpq($query_2) - OK 
SELECT t2.field_1 AS field_1, t2.field_2 AS field_2, 'table_two' AS table_name 
FROM 
{table_two} t2 

// dpq($query_3) - OK 
SELECT t3.field_1 AS field_1, t3.field_2 AS field_2, 'table_three' AS table_name 
FROM 
{table_three} t3 

// dpq($query_1->union($query_2)->union($query_3)) - OOPS.. 'table_one' all over the place 
SELECT t1.field_1 AS field_1, t1.field_2 AS field_2, 'table_one' AS table_name 
FROM 
{table_one} t1 UNION SELECT t2.field_1 AS field_1, t2.field_2 AS field_2, 'table_one' AS table_name 
FROM 
{table_two} t2 UNION SELECT t3.field_1 AS field_1, t3.field_2 AS field_2, 'table_one' AS table_name 
FROM 
{table_three} t3 

如果你有想法將是巨大的，因爲我一直在銀行我的頭與此一段時間...

Answer 1

睡了幾個小時後，我跟蹤它到這個功能：

// @file includes/database/select.inc 
    public function arguments() { 
    // .... 

    // If there are any dependent queries to UNION, 
    // incorporate their arguments recursively. 
    foreach ($this->union as $union) { 
     $args += $union['query']->arguments(); 
    } 

    return $args; 
    } 

而且由於查詢中的所有選擇都具有相同的鍵:table那麼你最終只會得到一個參數而不是你。

解決方案：只要確保你使用不同的密鑰的佔位符。

因此，如果我們在上面的例子中替換這些行（注意:table_1 & :table_2而不是:table：

$query_2->addExpression(':table_1', 'table_name', array(':table_1' => $table_name)); 
$query_3->addExpression(':table_2', 'table_name', array(':table_2' => $table_name)); 

瞧，終於得到預期的結果希望它可以幫助別人，半天失去努力的身影。爲什麼這是怎麼回事。

SELECT t1.field_1 AS field_1, t1.field_2 AS field_2, 'table_one' AS table_name 
FROM 
{table_one} t1 UNION ALL SELECT t2.field_1 AS field_1, t2.field_2 AS field_2, 'table_two' AS table_name 
FROM 
{table_two} t2 UNION ALL SELECT t3.field_1 AS field_1, t3.field_2 AS field_2, 'table_three' AS table_name 
FROM 
{table_three} t3