[英]How would I create a sub query in PHP?
所以我在一個現有的系統上工作,我試圖弄清楚他們如何進行mysql設置。 他們有這樣的查詢設置
$this->db->select('nID, nAID');
$this->db->where('bValid', 1);
$this->db->where('nID', (int)$nID);
$this->db->from('event');
$this->db->group_by('nID, nAID');
$query = $this->db->get();
而且此查詢的效果很好,但是我需要設置一個子查詢。 我已經用SQL編寫了查詢並對其進行了測試,以確認它是否有效,但是我在弄清楚如何翻譯它時遇到了麻煩。 基本上,我需要的不是從“事件”表中獲取,我需要從在此之前所做的子選擇中獲取。 我想像會怎樣。
$this->db->select('nID, nAID');
$this->db->where('bValid', 1);
$this->db->where('nID', (int)$nID);
$this->db->from(
$this->db->select('something, somethingelse');
$this->db->where('something', 1);
$this->db->get();
);
$this->db->group_by('nID, nAID');
$query = $this->db->get();
$this->db->select('nID, nAID');
$this->db->where('bValid', 1);
$this->db->where('nID', (int)$nID);
$this->db->from('event');
$this->db->group_by('nID, nAID');
轉換以從其中bValid = 1和nId ='$ nID'按nID分組的事件中選擇nID,nAID
您的子查詢
$this->db->select('nID, nAID');
$this->db->where('bValid', 1);
$this->db->where('nID', (int)$nID);
$this->db->from(
$this->db->select('something, somethingelse');
$this->db->where('something', 1);
$this->db->get();
);
$this->db->group_by('nID, nAID');
大致翻譯成
select nID, nAID select something,somethingelse where something=1 event where bValid=1 and nId='$nID' group by nID
我建議對循環中的每個記錄運行子查詢
步驟1:將此代碼放入DB_active_rec.php
// --------------------------------------------------------------------
/**
* Get SELECT query string
*
* Compiles a SELECT query string and returns the sql.
*
* @param string the table name to select from (optional)
* @param bool TRUE: resets QB values; FALSE: leave QB vaules alone
* @return string
*/
public function get_compiled_select($table = '', $reset = TRUE)
{
if ($table !== '')
{
$this->_track_aliases($table);
$this->from($table);
}
$select = $this->_compile_select();
if ($reset === TRUE)
{
$this->_reset_select();
}
return $select;
}
步驟2:嘗試
//Subquery
$this->db->select('something, somethingelse');
$this->db->where('something', 1);
$this->db->from('first_table');
$sub_query = $this->db->get_compiled_select();
$this->db->select('nID, nAID');
$this->db->where('bValid', 1);
$this->db->where('nID', (int)$nID);
$this->db->from("($sub_query) as tbl1");
$this->db->group_by('nID, nAID');
$query = $this->db->get();
告訴我是否可行。
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.