Question

我阅读了一些答案，但未能找到以下问题的正确答案。我有以下运行查询：

SELECT 
    mbr_src_code as 'C',
    cst_recno as 'ID',
    ind_first_name as 'FN',
    ind_last_name as 'LN',
    cst_org_name_dn as 'Company',
    cst_ixo_title_dn as 'Title',
    MAX(inv_trx_date) as 'Latest Transaction',
    inv_add_user as 'User',
    pyd_type as 'Type',
    bat_code as 'Code',
    mbr_add_user 'Add User',
    mbr_rejoin_date as 'rejoin',
    mbt_code,
    adr_state as 'state',
    adr_country as 'country',
    ivd_amount_cp
FROM 
    mb_membership  
JOIN 
    co_customer ON cst_key = mbr_cst_key AND mbr_delete_flag = 0  
LEFT JOIN 
    mb_member_type ON mbr_mbt_key = mbt_key 
LEFT JOIN 
    co_customer_x_address ON cxa_key = cst_cxa_key 
LEFT JOIN 
    co_address ON cxa_adr_key = adr_key 
LEFT JOIN 
    co_individual ON ind_cst_key = cst_key 
LEFT JOIN 
    mb_membership_x_ac_invoice ON mxi_mbr_key = mbr_key 
LEFT JOIN  
    ac_invoice ON mxi_inv_key = inv_key 
LEFT JOIN 
    ac_invoice_detail ON ivd_inv_key = inv_key 
LEFT JOIN 
    ac_payment_detail ON pyd_ivd_key = ivd_key 
LEFT JOIN 
    ac_payment ON pyd_pay_key = pay_key 
LEFT JOIN 
    ac_batch ON pay_bat_key = bat_key 
LEFT JOIN 
    ac_payment_info ON pay_pin_key = pin_key
LEFT JOIN 
    co_customer_x_customer ON cxc_cst_key_1 = co_customer.cst_key 
                           AND (cxc_end_date IS NULL OR DATEDIFF(dd, GETDATE(), cxc_end_date) >= 0) 
                           AND cxc_rlt_code = 'Chapter Member' 
LEFT JOIN 
    co_chapter ON cxc_cst_key_2 = chp_cst_key  
WHERE 
    (mbr_src_code LIKE N'%1DMFY18%' OR mbr_src_code LIKE N'%2DMFY18%' 
     OR mbr_src_code LIKE N'%INPhoneFY18%' OR mbr_src_code LIKE N'%OBTMFY18%' 
     OR mbr_src_code LIKE N'%3DMFY18%') 
    AND cst_recno = '20239'
GROUP BY  
    mbr_key, mbr_src_code, cst_recno, 
    ind_first_name, ind_last_name, cst_org_name_dn, cst_ixo_title_dn,
    inv_add_user, pyd_type, bat_code, mbr_add_user, mbr_rejoin_date,
    mbt_code, adr_state, adr_country, pin_cc_number_display, pin_cc_cardholder_name,
    ivd_amount_cp, chp_name
ORDER BY
    ind_last_name

我得到以下结果（样本）：

      C       ID    FN    LN       Company          Title       Latest transaction     User              Type          Code                    Add User    rejoin   mbt_code           state  country    ivd_amount_cp     
    2DMFY18 20239   Gus Bauman  Beveridge & Diamond Attorney    2013-09-23 00:00:00 Membership Renewal  Payment 2013-09-23-ULI-USD-C-SP-01  ULI_Conversion  NULL    Associate Member    DC  UNITED STATES   430.00  
    2DMFY18 20239   Gus Bauman  Beveridge & Diamond Attorney    2014-08-04 00:00:00 Membership Renewal  Payment 2014-08-04-ULI-USD-C-SP-01  ULI_Conversion  NULL    Associate Member    DC  UNITED STATES   430.00  
    2DMFY18 20239   Gus Bauman  Beveridge & Diamond Attorney    2015-09-02 00:00:00 Membership Renewal  Payment 2015-09-02-ULI-USD-C-SP-02  ULI_Conversion  NULL    Associate Member    DC  UNITED STATES   440.00  
    2DMFY18 20239   Gus Bauman  Beveridge & Diamond Attorney    2016-09-12 00:00:00 Membership Renewal  Payment 2016-09-12-ULI-USD-C-SP-01  ULI_Conversion  NULL    Associate Member    DC  UNITED STATES   440.00  
    2DMFY18 20239   Gus Bauman  Beveridge & Diamond Attorney    2017-09-22 00:00:00 Membership Renewal  Payment 2017-09-22-ULI-USD-C-SP-01  ULI_Conversion  NULL    Associate Member    DC  UNITED STATES   440.00

所以我的MAX函数不起作用（可能因为有其他列具有不同的值，就像在inv_trx_date中一样），什么是最好的替代方法？我想基本上接受整个查询并选择MAX（inv_trx_date）作为'最新交易'，每个唯一的cst_recno为'ID'。

Answer 1

我认为这个问题的规范答案如下：

with AllData as
(
select ... from ...
where ...
)
select * from allData ad1
inner join 
(
    select pk1, pk2, pk<n>, max(MaxThing) MaxVal 
    from AllData
    group by pk1, pk2, pk<n>
) as ad2 
on (ad1.pk1=ad2.pk1 and ad1.pk2=ad2.pk2 and ad1.pk<n>=ad2.pk<n> 
and  ad1.MaxThing=ad2.MaxVal)

在您的情况下，cst_recno是PK，inv_trx_date是MaxThing

Answer 2

MAX适用于您指定的整个组。如果您希望MAX汇总适用于每个唯一cst_recno，那么您只需要按每个唯一cst_recno进行分组。

Answer 3

重复行的问题是因为您的CODE和ivd_amount_cp列在记录集中包含非唯一值。如果它们都包含完全相同的信息，那么您的MAX函数可以正常工作。

您必须像其他人所建议的那样使用公用表表达式。假设您有一个包含特定CustomerID，订单日期以及许多其他信息的表。客户可以在同一天订购多个订单，无论出于何种原因，我们只对该客户的最新订单感兴趣。但是，我们确实希望查看与该订单相关的所有信息。

我们要做的第一件事就是建立一个CTE来确定最新的订单：

/* Example table */
CREATE TABLE myOrders
(
    OrderID int IDENTITY(1,1)
    , CustomerID int 
    , OrderDate datetime
    , ImportantInfo nvarchar(255)
)
;

/* Some test data to work with */
INSERT INTO myOrders 
VALUES (
    1, '01-01-2017', 'We do not want this row'
), (
    1, '01-02-2017', 'We do not want this row either'
),  (
    1, '01-10-2017', 'Getting closer, but not this one either'
),  (
    1, '01-10-2017', 'This is the one we want!'
)
;

WITH myMaxOrder AS 
(
    SELECT CustomerID, MAX(OrderID) AS MaxOrderID
    FROM myORders
    GROUP BY CustomerID
)

一旦确定了所需的MAX，就可以使用它来识别要检索的所有其他数据，方法是使用CTE使用刚刚获得的值连接回原始表在CTE：

SELECT 
    o.* 
FROM 
    MyOrders o
    JOIN myMaxOrder o1 ON o.CustomerID = o1.CustomerID 
    AND o1.MaxOrderID = o.OrderID

最大日期不起作用，另类？

3 个答案: