Question

我有这个SQL选择查询

SELECT * 
FROM bots 
WHERE id NOT IN (select botid 
                 from messages 
                 where messages.recipient = :recipient) 
limit 1

我需要做类似的事情：

SELECT * 
FROM bots 
[if isset(recipient = $recipient AND sender = $sender)] 
  WHERE id IN (select botid 
               from messages 
               where messages.recipient = :recipient and sender = :sender) 
else 
  WHERE id NOT IN (select botid 
                   from messages 
                   where messages.recipient = :recipient) 
limit 1

[] - 伪代码

如何进行此查询？

Bots表：

-------------------------------------------------------
| id       |  auth_token   |  messages_today  | vkid  |
-------------------------------------------------------
| 1       |  token   |                    0   | 2323  |
-------------------------------------------------------
| 2       |  token   |                     0  | 2343  |
-------------------------------------------------------

消息表：

-----------------------------------------------------------
| id       |  recipient   |  sender  | botid  | messageid |
-----------------------------------------------------------
| 1        |  12          |        1  |     1  |      3322 |
-----------------------------------------------------------
| 2        |  12          |        2  |     2  |    332123 |
-----------------------------------------------------------
| 3        |  13          |        1  |     1  |    332123 |
-----------------------------------------------------------

Answer 1

使用外连接

从机器人表中返回所有机器人
和来自匹配的消息talbe的数据
但是我们消除了仅返回机器人的匹配数据如果该特定机器人不存在提供收件人和发件人的邮件

返回所有机器人

Select * from bots B
LEFT JOIN messages M
  on M.BotID = B.ID
 and M.Sender = $sender
 and M.Recipient = $Recipient
Where M.BotID is null

WHERE子句中的Mysql和if / else语句

1 个答案: