如何将主表与 2 个表连接起来，以获取 2 个表中主表主 ID 的计数以及 codeigniter 中的主表信息

Question

我有一个主表，它的名字是“user”表，它包含用户的所有信息，有两个表“business_list”和“classified_list”。

我想显示所有用户信息，包括来自business_list 表的业务总数和来自classified_list 的分类总数 表

用户表

user_id    user_name     user_email         user_phone
-----------------------------------------------------     
001         Jose         jose@yahoo.in      457855654
002         Tom          tom@yahoo.in       5464644654
003         Nick         nick@yahoo.in      4545645644
004         Rose         rose@yahoo.in      554545441

business_list 表

bid        user_id      business_name
-----------------------------------------------
001        001          Construction business
002        003          Event business
003        001          Crane business
004        003          Furtinure business
005        004          Realestate business

classified_list 表：

cid      user_id       classified_name
-------------------------------------------    
001      001           Roller classified
002      004           Home classified
003      003           Chair classified
004      004           Office Classified
005      002           Light decoration classified

我想将信息显示为

User Name   User Email         User Phone     No Of Business     No Of Classified
---------------------------------------------------------------------------------
Jose        jose@yahoo.in      457855654           2                   1
Tom         tom@yahoo.in       5464644654          0                   1
Nick        nick@yahoo.in      4545645644          2                   1
Rose        rose@yahoo.in      554545441           1                   2

那么获取此结果的 mysql join 查询是什么，我使用的是 php codeigniter 3.0 框架，所以很好，如果有人知道 codeigniter 查询这个结果？

Answer 1

此查询将为您提供所需的结果。它将user 表连接到business_list 和classified_list 表中的UNION，并使用条件聚合来汇总与每个用户关联的企业和分类的数量：

SELECT u.user_name AS `User Name`,
       u.user_email AS `User Email`,
       u.user_phone AS `User Phone`,
       SUM(CASE WHEN bc.type = 'business' THEN 1 ELSE 0 END) AS `No Of Business`,
       SUM(CASE WHEN bc.type = 'classified' THEN 1 ELSE 0 END) AS `No Of Classified`
FROM user u
JOIN (SELECT 'business' AS type, user_id 
      FROM business_list
      UNION ALL
      SELECT 'classified' AS type, user_id
      FROM classified_list) bc
ON bc.user_id = u.user_id
GROUP BY u.user_id;

或者，您可以对每个表使用LEFT JOIN，COUNTing DISTINCT 来自每个表的值：

SELECT u.user_name AS `User Name`,
       u.user_email AS `User Email`,
       u.user_phone AS `User Phone`,
       COUNT(DISTINCT b.bid) AS `No Of Business`,
       COUNT(DISTINCT c.cid) AS `No Of Classified`
FROM user u
LEFT JOIN business_list b ON b.user_id = u.user_id
LEFT JOIN classified_list c ON c.user_id = u.user_id
GROUP BY u.user_id

两个查询的输出是一样的：

User Name   User Email      User Phone  No Of Business  No Of Classified
Jose        jose@yahoo.in   457855654   2               1
Tom         tom@yahoo.in    5464644654  0               1
Nick        nick@yahoo.in   4545645644  2               1
Rose        rose@yahoo.in   554545441   1               2

SQLFiddle Demo

Answer 2

试试这样的。

select u.user_name, u.user_email, u.user_phone, count(distinct b.bid),
       count(distinct c.cid) from user_table u 
   left outer join business_list b 
       on  u.user_id=b.user_id 
   left outer join classified_list c 
       on c.user_id=u.user_id 
group by 
    u.user_name,u.user_email,u.user_phone