sql - 需要不使用子查询的查询

Question

我的桌子是

PROPOSAL_TABLE
  PID   QUOTE_ID   PDF1
  ---   --------   ----
   1       123      null
   2       123      null
   3       123      null
   4       152      null
   5       888      null

我需要选择带有 MAX PID 的报价 ID。我有一个查询：

 SELECT PROPOSAL_PDF FROM PROPOSAL_TBL WHERE QUOTE_ID = '123' 
 AND PID = (SELECT MAX(PID) FROM PROPOSAL_TBL WHERE QUOTE_ID = '123')  

如何在不使用子查询的情况下获取值？

Answer 1

在不使用子查询的情况下，您可以使用 KEEP 子句：

select max(pid) as pid
     , max(quote_id) keep ( dense_rank first order by pid desc ) as quote_id
     , max(pdf1) keep ( dense_rank first order by pid desc ) as pdf1
  from proposal_table
 where quote_id = '123'

这应该是高效的，但一如既往的测试。我建议阅读Rob van Wijk 的博客文章。

标准的替代方法是使用子查询，但不需要使用分析函数再次扫描表，例如ROW_NUMBER()

select pid, quote_id, pdf1
  from ( select a.*, row_number() over ( order by pid ) as rn 
           from proposal_table a
          where quote_id = '123' )
 where rn = 1

Answer 2

您可以使用分析：

SQL> WITH DATA AS (
  2            SELECT 1 pid, 123 quote_id, 'A' pdf1 FROM DUAL
  3  UNION ALL SELECT 2 pid, 123 quote_id, 'B' pdf1 FROM DUAL
  4  UNION ALL SELECT 3 pid, 123 quote_id, 'C' pdf1 FROM DUAL
  5  UNION ALL SELECT 4 pid, 152 quote_id, 'D' pdf1 FROM DUAL
  6  UNION ALL SELECT 5 pid, 888 quote_id, 'E' pdf1 FROM DUAL
  7  )
  8  SELECT DISTINCT first_value(pid) over (ORDER BY pid DESC) pid,
  9                  quote_id,
 10                  first_value(pdf1) over (ORDER BY pid DESC) pdf1
 11    FROM DATA
 12   WHERE quote_id = 123;

       PID   QUOTE_ID PDF1
---------- ---------- ----
         3        123 C

您还可以使用聚合：

SQL> WITH DATA AS (
  2            SELECT 1 pid, 123 quote_id, 'A' pdf1 FROM DUAL
  3  UNION ALL SELECT 2 pid, 123 quote_id, 'B' pdf1 FROM DUAL
  4  UNION ALL SELECT 3 pid, 123 quote_id, 'C' pdf1 FROM DUAL
  5  UNION ALL SELECT 4 pid, 152 quote_id, 'D' pdf1 FROM DUAL
  6  UNION ALL SELECT 5 pid, 888 quote_id, 'E' pdf1 FROM DUAL
  7  )
  8  SELECT MAX(pid),
  9         quote_id,
 10         MAX(pdf1) KEEP (DENSE_RANK FIRST ORDER BY pid DESC) pdf1
 11    FROM DATA
 12   WHERE quote_id = 123
 13   GROUP BY quote_id;

  MAX(PID)   QUOTE_ID PDF1
---------- ---------- ----
         3        123 C

Answer 3

Sql 服务器

SELECT TOP 1 PROPOSAL_PDF  
FROM PROPOSAL_TBL 

WHERE QUOTE_ID = '123' 
ORDER BY  PID desc

甲骨文

SELECT * from (Select * FROM PROPOSAL_TBL 
               WHERE QUOTE_ID = '123' 
               ORDER BY  PID desc)
WHERE ROWNUM <=1

Answer 4

尝试这个 ：：

SELECT PROPOSAL_PDF 
FROM PROPOSAL_TBL WHERE QUOTE_ID = '123' 
ORDER BY  PID desc limit 1