使用 SUM() 将 MySQL 查询语句转换为 Codeigniter 活动记录样式查询语句答案

【问题标题】：MySQL Query Statement converted to Codeigniter Active record style query statement with SUM()使用 SUM() 将 MySQL 查询语句转换为 Codeigniter 活动记录样式查询语句
【发布时间】：2012-10-22 18:03:01
【问题描述】：

我正在尝试找出转换此 mysql 查询的最佳方法

SELECT
        SUM(invite.friendID = $mID AND invite.decidedwhen = '0000-00-00 00:00:00' AND evnt.ends >= '$event_ts' and invite.isactive = 0 and evnt.isactive = 0) AS invites_undecided,
        SUM(invite.friendID = $mID AND invite.decidedwhen != '0000-00-00 00:00:00' AND invite.yes = 1 AND evnt.ends >= '$event_ts' and invite.isactive = 0) and evnt.isactive = 0 AS invites_yes,
        SUM(invite.friendID = $mID AND invite.decidedwhen != '0000-00-00 00:00:00' AND invite.no = 1 AND evnt.ends >= '$event_ts' and invite.isactive = 0 and evnt.isactive = 0) AS invites_no,
        SUM(invite.friendID = $mID AND invite.decidedwhen != '0000-00-00 00:00:00' AND invite.maybe = 1 AND evnt.ends >= '$event_ts' and invite.isactive = 0 and evnt.isactive = 0) AS invites_maybe
FROM user_event_invite AS invite
JOIN user_event AS evnt ON evnt.eID = invite.eID

到使用 Codeigniters 活动记录格式的东西。 EG

$this->db->select()
  ->from('user_event')
  ->... something?

标准的 mysql 语句可以正常工作。但是以坚持统一的名义，我想使用活动记录。有什么办法吗？我找不到 SUM() 的任何内容

【问题讨论】：

我在指南中上下搜索了类似的内容，但找不到。但是我仍然有一点障碍，因为它没有出现（基于我现在找到的指南）我可以多次使用select_sum，如果可以的话？我如何像上面提到的SUM() 一样考虑各种条件？

标签： php mysql codeigniter activerecord

【解决方案1】：

      Like that you can write query :
    ==================================
     $query="SELECT SUM(case when invite.friendID = " . $mID ." AND 
     invite.decidedwhen = '0000-00-00 00:00:00' AND evnt.ends >= '" . $event_ts . "'
     and invite.isactive = 0 and evnt.isactive = 0) AS invites_undecided,...       
     FROM user_event_invite AS invite
      left outer JOIN user_event AS evnt ON evnt.eID = invite.eID"

【讨论】：

【解决方案2】：

（更多的是评论而不是答案，因为我没有测试过它；但它可能仍然有帮助）

活动记录有一个$this->db->select_sum(); 函数，并且（这是我不确定的一点）您可能可以使用方法链。所以这里有一些东西可以尝试。

第 1 阶段是将常见的东西剥离到 WHERE 中。如果 WHERE 被索引，它会加快速度。这会给你（括号也固定 - 你的 SQL 有错误）

SELECT
    SUM(invite.decidedwhen = '0000-00-00 00:00:00') AS invites_undecided,
    SUM(invite.decidedwhen != '0000-00-00 00:00:00' AND invite.yes = 1 ) AS invites_yes,
    SUM(invite.decidedwhen != '0000-00-00 00:00:00' AND invite.no = 1) AS invites_no,
    SUM(invite.decidedwhen != '0000-00-00 00:00:00' AND invite.maybe = 1) AS invites_maybe
FROM user_event_invite AS invite
   JOIN user_event AS evnt ON evnt.eID = invite.eID
WHERE invite.friendID = $mID  AND evnt.ends >= '$event_ts' and invite.isactive = 0 AND evnt.isactive = 0

此外，如果您可以通过sayign 接受来简化，使yes，no，也许都是排他性的，那么您也可以去掉“decidedwhen”以进一步简化。（理想情况下，您只需要一个“COUNT”并减去其余部分，但不清楚如何在对活动记录的一个查询中执行此操作）。

SELECT
    SUM(invite.decidedwhen = '0000-00-00 00:00:00') AS invitees_undecided,
    SUM(invite.yes = 1 ) AS invites_yes,
    SUM(invite.no = 1) AS invites_no,
    SUM(invite.maybe = 1) AS invites_maybe
FROM user_event_invite AS invite
   JOIN user_event AS evnt ON evnt.eID = invite.eID
WHERE invite.friendID = $mID  AND evnt.ends >= '$event_ts' AND invite.isactive = 0 AND evnt.isactive = 0

现在将它用于活动记录上的方法链：

$this->db->select_sum('invite.decidedwhen = '0000-00-00 00:00:00', 'invite_undecided')
  ->select_sum('yes', 'invite_yes')
  ->select_sum('no', 'invite_no')
  ->etc
  ->from('user_event_invite')
  ->join('user_event', 'user_event.eID=user_event_invite.eID)
  ->where('friendID', '$mID')
  ->where('user_event.ends >=', $event_ts)
  -> etc

【讨论】：