Question

我有2个表 - 1个包含父记录，1个包含子记录。对于每个父记录，我正在尝试使用MAX（SalesPriceEach）返回单个子记录。

此外，我只想在有超过1个子记录时返回一个值。

parent - SalesTransactions table:
+-------------------+---------+
|SalesTransaction_ID|   text  |
+-------------------+---------+
| 1                 |  Blah   |
| 2                 |  Blah2  |
| 3                 |  Blah3  |
+-------------------+---------+

child - SalesTransactionLines table 
+--+-------------------+---------+--------------+
|id|SalesTransaction_ID|StockCode|SalesPriceEach|
+--+-------------------+---------+--------------+
| 1|   1               |  123    | 99           |
| 2|   1               |   35    | 50           |
| 3|   2               |   15    | 75           |
+--+-------------------+---------+--------------+


 desired results
+-------------------+---------+--------------+
|SalesTransaction_ID|StockCode|SalesPriceEach|
+-------------------+---------+--------------+
|   1               |  123    | 99           |
|   2               |   15    | 75           |
+-------------------+---------+--------------+

我发现了一个非常相似的问题here，根据我对答案的查询，但没有看到我期望的结果。

WITH max_feature AS (
   SELECT c.StockCode,
          c.SalesTransaction_ID,
          MAX(c.SalesPriceEach)  as feature
     FROM SalesTransactionLines c
 GROUP BY c.StockCode, c.SalesTransaction_ID)
   SELECT p.SalesTransaction_ID,
          mf.StockCode,
          mf.feature
     FROM SalesTransactions p
LEFT JOIN max_feature mf ON mf.SalesTransaction_ID = p.SalesTransaction_ID

此查询的结果是为每个父级返回多行，而不是首先返回最高值！

Answer 1

我知道我参加这个派对已经晚了一年但我总是喜欢在这些情况下使用Row_Number。当有两行符合您的Max条件并确保只返回一行时，它解决了这个问题：

with z as (
select 
    st.SalesTransaction_ID
    ,row=ROW_NUMBER() OVER(PARTITION BY st.SalesTransaction_ID ORDER BY stl.SalesPriceEach DESC)
    ,stl.StockCode
    ,stl.SalesPriceEach
from 
    SalesTransactions st
    inner join SalesTransactionLines stl on stl.SalesTransaction_ID = st.SalesTransaction_ID
)
select * from z where row = 1

Answer 2

select stl.SalesTransaction_ID, stl.StockCode, ss.MaxSalesPriceEach
from SalesTransactionLines stl
inner join 
(
    select stl2.SalesTransaction_ID, max(stl2.SalesPriceEach) MaxSalesPriceEach
    from SalesTransactionLines stl2 
    group by stl2.SalesTransaction_ID
    having count(*) > 1
) ss on (ss.SalesTransaction_ID = stl.SalesTransaction_ID and 
         ss.MaxSalesPriceEach = stl.SalesPriceEach)

OR，或者：

SELECT stl1.*
FROM SalesTransactionLines AS stl1
LEFT OUTER JOIN SalesTransactionLines AS stl2
ON (stl1.SalesTransaction_ID = stl2.SalesTransaction_ID 
    AND stl1.SalesPriceEach < stl2.SalesPriceEach)
WHERE stl2.SalesPriceEach IS NULL;

Answer 3

SELECT SalesTransactions.SalesTransaction_ID, 
       SalesTransactionLines.StockCode, 
       MAX(SalesTransactionLines.SalesPriceEach) 
FROM  SalesTransactions RIGHT JOIN SalesTransactionLines 
      ON SalesTransactions.SalesTransaction_ID = SalesTransactionLines.SalesTransaction_ID 
GROUP BY SalesTransactions.SalesTransaction_ID, alesTransactionLines.StockCode;

Answer 4

select a.SalesTransaction_ID, a.StockCode, a.SalesPriceEach
from SalesTransacions as a 
  inner join (select SalesTransaction_ID, MAX(SalesPriceEach) as SalesPriceEach  
              from SalesTransactionLines group by SalesTransaction_ID) as b
    on a.SalesTransaction_ID = b.SalesTransaction_ID 
       and a.SalesPriceEach = b.SalesPriceEach

子查询返回带有trans id及其最大值的表，所以只需将这两个值与事务表本身连接起来

SQL为每个父行返回子项的最大值

4 个答案: