MYSQL限制左连接查询

我有一个查询，它使用一些左连接来返回数据。进退两难的是，我想

限制

，还想

按

排序左联接之一的结果，从而限制返回的行总数

我试图订购和限制的表格是

table4

我的查询：

SELECT SQL_CALC_FOUND_ROWS e.meta_1, a.requestid, b.clientid, c.job_description, d.forename
FROM quotations_request AS a 

 LEFT JOIN table1 AS b ON (a.assigned_to = b.userid) 
 LEFT JOIN table2 AS c ON (a.job_costing = c.jobid) 
 LEFT JOIN table3 AS d ON (a.clientid = d.clientid) 
 LEFT JOIN table4 AS e ON (e.quotationid = a.requestid)

 WHERE a.archived = '0' AND (e.meta_1 = LCASE('requested') )

SELECT SQL_CALC_FOUND_ROWS statuss.meta_1, a.requestid, b.clientid, c.job_description, d.forename,
 FROM quotations_request AS a 

 LEFT JOIN table1 AS b ON (a.assigned_to = b.userid) 
 LEFT JOIN table2 AS c ON (a.job_costing = c.jobid) 
 LEFT JOIN table3 AS d ON (a.clientid = d.clientid) 
 LEFT JOIN (Select meta_1 from table4 where quotationid = a.requestid ORDER BY uploaded_date DESC LIMIT 0, 1) 
 as statuss ON (statuss.quotationid = a.requestid)

 WHERE a.archived = '0' AND (statuss.meta_1 = LCASE('requested') )

我尝试过的：

SELECT SQL_CALC_FOUND_ROWS e.meta_1, a.requestid, b.clientid, c.job_description, d.forename
FROM quotations_request AS a 

 LEFT JOIN table1 AS b ON (a.assigned_to = b.userid) 
 LEFT JOIN table2 AS c ON (a.job_costing = c.jobid) 
 LEFT JOIN table3 AS d ON (a.clientid = d.clientid) 
 LEFT JOIN table4 AS e ON (e.quotationid = a.requestid)

 WHERE a.archived = '0' AND (e.meta_1 = LCASE('requested') )

SELECT SQL_CALC_FOUND_ROWS statuss.meta_1, a.requestid, b.clientid, c.job_description, d.forename,
 FROM quotations_request AS a 

 LEFT JOIN table1 AS b ON (a.assigned_to = b.userid) 
 LEFT JOIN table2 AS c ON (a.job_costing = c.jobid) 
 LEFT JOIN table3 AS d ON (a.clientid = d.clientid) 
 LEFT JOIN (Select meta_1 from table4 where quotationid = a.requestid ORDER BY uploaded_date DESC LIMIT 0, 1) 
 as statuss ON (statuss.quotationid = a.requestid)

 WHERE a.archived = '0' AND (statuss.meta_1 = LCASE('requested') )

结果：

SELECT SQL_CALC_FOUND_ROWS e.meta_1, a.requestid, b.clientid, c.job_description, d.forename
FROM quotations_request AS a 

 LEFT JOIN table1 AS b ON (a.assigned_to = b.userid) 
 LEFT JOIN table2 AS c ON (a.job_costing = c.jobid) 
 LEFT JOIN table3 AS d ON (a.clientid = d.clientid) 
 LEFT JOIN table4 AS e ON (e.quotationid = a.requestid)

 WHERE a.archived = '0' AND (e.meta_1 = LCASE('requested') )

SELECT SQL_CALC_FOUND_ROWS statuss.meta_1, a.requestid, b.clientid, c.job_description, d.forename,
 FROM quotations_request AS a 

 LEFT JOIN table1 AS b ON (a.assigned_to = b.userid) 
 LEFT JOIN table2 AS c ON (a.job_costing = c.jobid) 
 LEFT JOIN table3 AS d ON (a.clientid = d.clientid) 
 LEFT JOIN (Select meta_1 from table4 where quotationid = a.requestid ORDER BY uploaded_date DESC LIMIT 0, 1) 
 as statuss ON (statuss.quotationid = a.requestid)

 WHERE a.archived = '0' AND (statuss.meta_1 = LCASE('requested') )

尝试上述操作后，我发现一个错误，即where子句中的

a.requestid

未知（对于最后一个左连接）

尝试以下操作：

SELECT SQL_CALC_FOUND_ROWS statuss.meta_1, a.requestid, b.clientid, c.job_description, d.forename
 FROM quotations_request AS a 

 LEFT JOIN table1 AS b ON (a.assigned_to = b.userid) 
 LEFT JOIN table2 AS c ON (a.job_costing = c.jobid) 
 LEFT JOIN table3 AS d ON (a.clientid = d.clientid) 
 LEFT JOIN (
    select *
    from (select
            t.*,
            @rn := if(quotationid = @qid, @rn + 1, 
                if(@qid := quotationid, 1, 1)
            ) rn
        from (
        select *
        from table4
        order by quotationid, uploaded_date desc) t cross join (
            select @rn := 0, @qid := -1
        ) t2
    ) t where rn = 1
) 
 as statuss ON (statuss.quotationid = a.requestid)

 WHERE a.archived = '0' AND (statuss.meta_1 = LCASE('requested') )

---

用户变量@rn和@qid用于从表4中找到最新上传日期的前1行，然后将其与其他表连接起来

，并且在子查询中使用

LIMIT

，这似乎是合理的……那么接下来会发生什么呢？@TimBiegeleisen抱歉，我应该添加（更新的问题）我最后的错误是“a.requestid”这是一个未知领域。记住a.requestid来自第二行的主表第一段中描述的困境与阻止查询运行的错误无关。在您的第一个查询中给定基于e.meta_l的谓词，左连接是一种非常低效的冗余，应该是内部连接。。。其中e与内连接e相同。此外，使用区分大小写的排序规则也不常见。只需说“我收到一个SQL错误，告诉我检查手册”来自webmanage“按quotationid上传订单，上传日期描述）t cros”这是我从您的答案中粘贴的代码（带有与我相关的修改字段名），它看起来正确吗？我无法访问上述网站。我已经更新了我的答案。你能试试吗？子问题中缺少了一个

*

“有一天我能像你一样吗？@jimmyturner过早的神化和过早的优化一样糟糕；-）