Question

简要说明......我有4张桌子。 “联系人”（每个人的列表，唯一ID），contact_phones（每个联系人的多个电话号码，contact_id上的联接）和contact_communication（每次我们与此联系人交谈，加入contact_id时）和学校（a学校名单，加入学校.school_id = contacts.contact_id）。

我需要什么：我需要找一所学校。对于那所学校，我需要一份每个人的名单，他们的主要电话号码，以及我们与他们的最后一次沟通（如果有的话）。

问题是，如果我们没有与他们沟通，他们就不会出现在列表中。如果我在“WHERE”子句中取出“AND”语句，那么我会获得多个通信记录。我只想要最新的通讯记录，但我想要所有联系人。但有些联系人没有通讯记录。

这是我的疑问：

SELECT c.id,
            c.f_name,
            c.l_name,
            c.address1,
            c.address2,
            c.city,
            c.state,
            c.zip,
            c.tel,
            c.school_id,
            c.email,
                ct.tel,
                cc.date,
                cc.reason,
                cc.result,
                cc.caller
                FROM contacts AS c
                LEFT OUTER JOIN contact_phones AS ct ON c.id = ct.contact_id
                LEFT OUTER JOIN contact_communication AS cc ON c.id = cc.contact_id 
            WHERE school_id = '$schoolId' AND 
                cc.id IN (SELECT MAX(id) FROM contact_communication WHERE contact_id = c.id)
                ORDER BY cc.date DESC

问题是，这个查询只给我最新的通讯（这是我想要的），但不会列出没有通讯的联系人。

我已经在这3天了。有什么提示吗？

谢谢！

（PS：如果需要，我会编辑并提供更多信息。）

修改答案（谢谢，ysrb）正在改变我的where子句：

SELECT c.id,
            c.f_name,
            c.l_name,
            c.address1,
            c.address2,
            c.city,
            c.state,
            c.zip,
            c.tel,
            c.school_id,
            c.email,
                ct.tel,
                cc.date,
                cc.reason,
                cc.result,
                cc.caller
                FROM contacts AS c
                LEFT OUTER JOIN contact_phones AS ct ON c.id = ct.contact_id
                LEFT OUTER JOIN contact_communication AS cc ON c.id = cc.contact_id 
            WHERE school_id = '$schoolId' AND 
                (cc.id IN (SELECT MAX(id) FROM contact_communication WHERE contact_id = c.id) OR cc.id IS NULL) 
                ORDER BY cc.date DESC

Answer 1

尝试：

SELECT c.id,
            c.f_name,
            c.l_name,
            c.address1,
            c.address2,
            c.city,
            c.state,
            c.zip,
            c.tel,
            c.school_id,
            c.email,
                ct.tel,
                cc.date,
                cc.reason,
                cc.result,
                cc.caller
                FROM contacts AS c
                LEFT OUTER JOIN contact_phones AS ct ON c.id = ct.contact_id
                LEFT OUTER JOIN contact_communication AS cc ON c.id = cc.contact_id 
            WHERE school_id = '$schoolId' AND 
                (cc.id = (SELECT MAX(id) FROM contact_communication WHERE contact_id = c.id) OR cc.ID IS NULL)
            ORDER BY cc.date DESC

3表左外连接不适用于子查询

1 个答案: