Mysql选择其中t4.name=x和t2或t3有一个t1.user！？：）

为了解释我的问题，让我们想象4张表

users - (userid, user.data)

buy - (buyid, productid, userid, buy.conditions)

sell - (sellid, productid, userid, sell.conditions)

产品-（productid，product.data）

我想做一个选择，当有一个用户要购买或销售名称上有X的产品时，返回所有用户和产品数据

SELECT userid, 
       USER.DATA, 
       productid, 
       product.DATA 
FROM   users, 
       buy, 
       sell, 
       products 
WHERE  ( buy.userid = users.userid 
          OR sell.userid = users.userid ) 
       AND ( buy.productid = product.productid 
              OR buy.productid = product.productid ) 
       AND product.DATA LIKE '%x%'  

---

这是行不通的，但我相信你知道我在努力做什么。

试试下面这样的工会：

SELECT userid, 
       USER.DATA, 
       productid, 
       product.DATA 
FROM   users, 
       buy, 
       products 
WHERE  (buy.userid = users.userid) 
  AND  (buy.productid = product.productid)
  AND  product.DATA LIKE '%x%'  
UNION 
SELECT userid, 
       USER.DATA, 
       productid, 
       product.DATA 
FROM   users, 
       sell, 
       products 
WHERE  (sell.userid = users.userid ) 
  AND  (sell.productid = product.productid ) 
  AND  product.DATA LIKE '%x%'  

---

您可以使用EXISTS子句：

SELECT userid, 
       USER.DATA, 
       productid, 
       product.DATA 
FROM   users, 
       products 
WHERE  ( EXISTS (SELECT * 
             FROM   buy 
                    INNER JOIN product 
                      ON ( buy.productid = product.productid ) 
             WHERE  buy.userid = users.userid 
                    AND product.DATA LIKE '%x%') ) 
        OR ( EXISTS (SELECT * 
                 FROM   sell 
                        INNER JOIN product 
                          ON ( sell.productid = product.productid ) 
                 WHERE  sell.userid = users.userid 
                        AND product.DATA LIKE '%x%') 

        AND products.userid = users.userid)

谢谢大家

在朋友的帮助下，最终做出了如下的事情：

SELECT USER.DATA, 
      product.DATA, origem
From
(
SELECT 'b' Origem,
   productid, 
   userid 
FROM buy
union all
SELECT 's' Origem,
   productid, 
   userid 
FROM sell
) tabelas
inner join users on users.userid=tabelas.userid
inner join products on products.productid=tabelas.productid
Where product.DATA LIKE '%x%'