我有四个表需要连接在一起,其中一个表有两个不同的记录需要获取。guildparty表我得到了它们的名称,这样我就可以向用户显示名称而不是ID,charlog表也有我想要显示的char-ID的创建日期和最后登录日期。这是桌子:
char表格:

----------------------------------------------------
| char_id    | name    | guild_id    | party_id    |
|---------------------------------------------------
| 150000     | char1   | 3           | 3           |
| 150001     | char2   | 2           | (NULL)      |
| 150002     | char3   | (NULL)      | 1           |
| 150003     | char4   | 1           | 2           |
----------------------------------------------------

guild表格:
-------------------------
| guild_id   | name     |
-------------------------
| 1          | guild_1  |
| 2          | guild_2  |
| 3          | guild_3  |
-------------------------

party表格:
-------------------------
| party_id   | name     |
-------------------------
| 1          | party_1  |
| 2          | party_2  |
| 3          | party_3  |
-------------------------

charlog表格:
----------------------------------------------------
| time                 | char_id   | char_msg      |
----------------------------------------------------
| 2015-02-14 06:45:32  | 150000    | make new char |
| 2015-02-14 06:45:58  | 150000    | char select   |
| 2015-02-15 12:32:19  | 150001    | make new char |
| 2015-02-15 16:54:01  | 150000    | char select   |
| 2015-02-15 19:23:54  | 150001    | char select   |
| 2015-02-16 01:32:13  | 150002    | make new char |
| 2015-02-16 01:33:01  | 150003    | make new char |
| 2015-02-16 04:45:43  | 150000    | char select   |
| 2015-02-16 07:43:22  | 150003    | char select   |
----------------------------------------------------

如前所述,我需要从make new char表中获取charlog条目,以便在创建角色时显示,以及在播放角色时显示的最后一个(按日期)条目,所有这些都使用一个char_id。
总之,我想找一张这样的桌子:
---------------------------------------------------------------------------------------------------------------------
| char_id    | name     | guild_id | guild_name | party_id | party_name | create_time         | lastlogin_time      |
---------------------------------------------------------------------------------------------------------------------
| 150000     | char1    | 3        | guild_3    | 3        | party_3    | 2015-02-14 06:45:32 | 2015-02-16 04:45:43 |

我在Codeigniter中使用以下活动记录行来尝试获取所需的数据。它正确返回创建日期,但不返回上次登录时间(为空):
function get_char_info($cid) {
    $this->db->select('char.*,guild.guild_id,guild.name AS guild_name,party.party_id,party.name AS party_name,charlog1.time AS create_time,charlog2.time AS lastlogin_time');
    $this->db->from('char');
    $this->db->where('char.char_id', $cid);
    $this->db->join('guild', 'char.guild_id = guild.guild_id', 'left');
    $this->db->join('party', 'char.party_id = party.party_id', 'left');
    $this->db->join('charlog AS charlog1', 'char.char_id = charlog1.char_id AND charlog1.char_msg = "make new char"', 'left');
    $this->db->join('charlog AS charlog2', 'char.char_id = charlog2.char_id AND charlog2.char_msg = (SELECT max(charlog.time) FROM charlog WHERE char_msg = "char select")', 'left');
    $query = $this->db->get();
    return $query->row();
}

如前所述,公会名称、政党名称和创建时间正确通过,但上次登录时间为空,没有错误。
我试过在活动记录子句中混淆一些东西,但无法显示上次登录的时间。任何帮助都将不胜感激。

最佳答案

子查询上的联接不正确:
应该charlog2.time = (SELECT....)而不是charlog2.char_msg = (SELECT....)

08-07 17:58