Question

我想从表tblquoteproposal`中检索最近的requestid以获取特定的customerId这里3，在这个例子中ID 2＆amp; ID 4。

表tblrequest requestid Customerid 6 2 7 4 8 3 9 3

表tblquoteproposal

 id requestid QuotePraposalLink comment
 1  6          jgj               mghm   
 2  7         jhgj               hjgj  
 3  8         xyz1              rifsf
*4  8         xyz2              ri2sf*
 5  9         xyz3              ri3sf
*6  9         xyz4              ri4sf*

在此表中requestid是外键。还有另一个表tblrequest，其中requestid为主键。

我写了以下查询，但它没有给我正确的结果：

SELECT r.RequestId,r.ConsultantId,(SELECT concat(FirstName,' ',LastName) 
                                   FROM tbluser 
                                   WHERE UserId = v_userId) as "Customer",
       r.RequestDate,r.QuoteDetailsFileLink,r.Requestcomment,r.CustomerId,
       qp.QuotePraposalLink,qp.Comment
FROM tblrequest r
LEFT OUTER JOIN tblquoteproposal qp ON r.RequestId=qp.RequestId 
WHERE r.customerid=v_userId 
GROUP BY r.RequestId 
ORDER BY qp.id ;

Answer 1

为什么不尝试：

SELECT MAX(id)
FROM tblquoteproposal
GROUP BY requestid

并将此查询的结果提供给您需要的任何内容？（这可以是子查询）。

例如，您的完整解决方案可能如下（我使用LEFT OUTER JOIN，因为您这样做，我不确定它是正确的方式，也许INNER JOIN更合适）：</ p>

SELECT ... your fields ...
FROM 
    tblquoteproposal p LEFT OUTER JOIN tblrequest r 
        on p.requestid = r.requestid
WHERE p.id IN (
    SELECT MAX(id)
    FROM tblquoteproposal
    GROUP BY requestid )

Answer 2

SELECT  *
FROM    (
        SELECT  requestid, MAX(id) AS mid
        FROM    tblquoteproposal
        GROUP BY
                requestid
        ) m
JOIN    tblrequest tr
ON      tr.id = tm.requestid
JOIN    tblquoteproposal tqp
ON      tqp.id = m.mid

Answer 3

Rax Olgud的优化版本答案可能是：

SELECT ... your fields ...
FROM 
    tblquoteproposal p LEFT OUTER JOIN tblrequest r 
        ON p.requestid = r.requestid
WHERE p.id = ifnull( (
    SELECT MAX(id)
    FROM tblquoteproposal
    where requestid = r.requestid ), p.id )

编辑使其成为外部联接。

检索最后（最新）明显的最高值

3 个答案: