Question

我有一个关于我正在处理的SQL脚本的问题

SELECT distinct companyid, 
       companyshortname, 
       loanamount, 
       employeename, 
       , employeerole, 
       MaxTime, 
       businessdescription
FROM       company
INNER JOIN loan ON companyfkey = loanfkey
LEFT JOIN (SELECT businessdescription_fkey, 
                  MAX(w.business_date_transaction_occured) AS MaxTime 
           FROM businessdescription w
           WHERE w.businessstatus <> 3    <-- this means that the company is still open
           GROUP BY w.businessdescription_fkey) wf 
ON company_fkey = businessdescriotion_fkey

这将返回给我所有状态不同于3的企业，但是我的第一个问题是它将所有状态为3的业务归还给我。

我的第二个问题是如何将其他值合并到跟踪中，例如Businessdescriptioncomment我会做这样的事情吗？

LEFT JOIN (SELECT businessdescription_fkey, 
                  MAX(w.business_date_transaction_occured) AS MaxTime ,
                  w.businessdescriptioncomment AS BusinessComment
           FROM   businessdescription w         
           WHERE  w.businessstatus <> 3 <-- this means that the company is open
           GROUP BY w.businessdescription_fkey) wf 
ON company_fkey = businessdescriotion_fkey

和我的变量BusinessComment到我的第一个选择？

感谢您的帮助。

Answer 1

而不是Left Join使用内部联接，因为它只会在公司打开时给出记录。另外，我在Sub查询中使用了self join来获取Business Comment，然后在外部选择查询中使用它

试试这个： -

SELECT distinct companyid, 
       companyshortname, 
       loanamount, 
       employeename, 
       , employeerole, 
       MaxTime, 
       businessdescription,
       BusinessComment
FROM       company a

INNER JOIN loan b
ON a.companyfkey = b.loanfkey

INNER JOIN
(
    SELECT a.businessdescription_fkey, a.MaxTime, w.businessdescriptioncomment AS BusinessComment
    FROM
    (
    SELECT businessdescription_fkey, 
                      MAX(w.business_date_transaction_occured) AS MaxTime 
               FROM   businessdescription w         
               WHERE  w.businessstatus <> 3 
               GROUP BY w.businessdescription_fkey
    ) a
    INNER JOIN
    businessdescription w
    ON a.businessdescription_fkey=w.businessdescription_fkey AND a.MaxTime=w.business_date_transaction_occured
    WHERE  w.businessstatus <> 3 
) c
ON a.company_fkey = c.businessdescriotion_fkey

如果您有任何问题，请告诉我

Answer 2

更改您的第二次加入：

INNER JOIN businessdescription w 
ON company_fkey = w.businessdescriotion_fkey 
and businessstatus <> 3

在你的选择中：

SELECT distinct companyid, 
         companyshortname, 
         loanamount, 
         employeename, 
         employeerole, 
         MaxTime, 
         businessdescription,
         w.businessdescriptioncomment
FROM  company

告诉我它是否适合你

Answer 3

在您的JOIN子查询中，您添加了过滤器 businessstatus＆lt;＆gt; 3 以排除ID 3.但这是LEFT JOIN。在这种情况下，它将带来第一个表格，在您的案例公司和加载中的所有内容。

用内部连接替换LEFT JOIN。

LEFT JOIN是否还有其他正当理由。

Answer 4

虽然你在子查询中给出了where条件（businessstatus＆lt;＆gt; 3），但它只过滤子查询，所以如果你用子查询做左连接，它会返回左表加右表的结果某行显示空列（在这种情况下（businessstatus == 3将为Null）

使用内部联接而不是左联接可以给出bussinessstatus＆lt;＆gt;的结果3

无法检索到正确的结果

4 个答案: