MySQL獲取行在同一表中存在相應的行

Question

我試圖根據某些基本的where子句從表中獲取行，現在我想在末尾包含「AND EXISTS」子句。我的代碼如下：

$stmt = $mysqli->prepare("SELECT object_id FROM ". 
      $db_table_prefix."user_events 
      WHERE LPAD(start_timestamp,15,'0') < LPAD(?,15,'0') 
      AND event_id = ? 
      AND EXISTS ( 
      SELECT * FROM ".$db_table_prefix."user_events 
       WHERE LPAD(start_timestamp,15,'0') > LPAD(?,15,'0') 
       AND event_id = ?) 
     "); 

我遇到的問題是，我不知道如何內指定從主查詢中的列值並存子查詢。

我正在尋找一種方法來此位釘成子查詢：

AND object_id = **object_id from main query** 

任何幫助表示讚賞

Answer 1

而且，爲子查詢的表添加別名以避免混淆

$stmt = $mysqli->prepare("SELECT object_id FROM ". 
     $db_table_prefix."user_events 
     WHERE LPAD(start_timestamp,15,'0') < LPAD(?,15,'0') 
     AND event_id = ? 
     AND EXISTS ( 
     SELECT * FROM ".$db_table_prefix."user_events AS u 
      WHERE LPAD(u.start_timestamp,15,'0') > LPAD(?,15,'0') 
      AND u.object_id = " .$db_table_prefix.".object_id 
      AND u.event_id = ?) 
    "); 

Answer 2

和OBJECT_ID中（從選擇OBJECT_ID ...

Answer 3

而不是EXISTS，你可能會發現自連接語法更清晰這裏，我不能演繹的正是你想要從你的代碼，但要獲得object_id爲在特定時間之前啓動的事件，並再次後來也開始：

SELECT ue1.object_id 
FROM user_events ue1 join user_events ue2 
WHERE ue1.event_id = ue2.event_id AND 
     ue1.object_id = ue2.object_id AND 
     ue1.event_id = ? AND 
     LPAD(ue1.start_timestamp, 15, '0') < LPAD(ue2.start_timestamp, 15, '0') AND 
     LPAD(ue1.start_timestamp, 15, '0') < LPAD(?, 15, '0')