“不同”导致复杂查询

Question

“不同”导致复杂查询

我有以下查询，它返回数据库中在两个给定日期之间进行交易的所有商家。

SELECT distinct me.id, me.merchant_num, me.merchant_nm, count(1) as num_transactions
       ,CASE WHEN me.status = 'A' THEN 'Yes' ELSE 'No' END as production_mode
FROM merchant_t me
LEFT OUTER JOIN transaction_t tt
    ON tt.merchant_id = me.id 
    AND tt.transaction_dt BETWEEN '2020-04-01' and '2020-04-30'
WHERE me.status = 'T'
GROUP BY me.id, me.merchant_num, me.merchant_nm, me.status

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但是，我需要在查询中包含其他信息。我写了下面的增强查询，但它会导致重复的商家。我知道查询可以写得更好，但这是我的 SQL 知识的限制。

我需要保持与上述查询相同数量的结果。

SELECT distinct me.id, me.merchant_num, me.merchant_nm, count(1) as num_transactions
       ,CASE WHEN me.status = 'A' THEN 'Yes' ELSE 'No' END as production_mode   

       -- additional information needed as below, with comments

       -- the date of the last transaction that uses IBank (IBA)
       ,(select max(transaction_dt) 
           from transaction_t where merchant_id = me.id 
           and tt.bank_txt = 'IBA') as last_ibank_transaction

       -- the value of the "trans_live" column for the merchant's most recent transaction
       ,(select top 1 trans_live          
           from transaction_t
           where merchant_id = me.id order by transaction_dt desc) is_live
FROM merchant_t me
    LEFT OUTER JOIN transaction_t tt
         ON tt.merchant_id = me.id 
         AND tt.transaction_dt BETWEEN '2020-04-01' and '2020-04-30'
    WHERE me.status = 'T'
    GROUP BY me.id, me.merchant_num, me.merchant_nm, me.status, tt.bank_txt

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这将返回重复的商家。在下面的屏幕截图中，我过滤了单个商家以显示重复。第一个结果集来自原始查询。第二个来自更新的查询。“DISTINCT”完成了它的工作，但我只想看到一个商家记录。

涉及到两个表：

merchant_t
----------
id     merchant_num    merchant_nm    status


transaction_t
--------------
id     merchant_id     transaction_dt     trans_live     bank_txt

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编辑

我试图避免在子查询中包含日期

瓦伦的回答

更新后的查询返回许多重复项，如下所示。

SQL 脚本

USE [XYZ]
GO
/****** Object:  Table [dbo].[merchant_t]    Script Date: 6/10/2020 5:23:51 PM ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[merchant_t](
    [id] [int] IDENTITY(1,1) NOT NULL,
    [merchant_num] [nvarchar](50) NULL,
    [merchant_nm] [nvarchar](100) NULL,
    [status] [nchar](1) NULL
) ON [PRIMARY]
GO
/****** Object:  Table [dbo].[transaction_t]    Script Date: 6/10/2020 5:23:51 PM ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[transaction_t](
    [id] [int] IDENTITY(1,1) NOT NULL,
    [merchant_id] [int] NULL,
    [transaction_dt] [datetime] NULL,
    [trans_live] [bit] NULL,
    [bank_txt] [nvarchar](30) NULL
) ON [PRIMARY]
GO
SET IDENTITY_INSERT [dbo].[merchant_t] ON 
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (335, N'PriceBusterDVD_NZ_AN', N'Pricebuster NZ ANZ', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (341, N'T6400050', N'Merco Test Merchant', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (342, N'6400262', N'Musac School Test 1', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (366, N'T6400093', N'Paystation Limited Test', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (367, N'T6400435', N'PB Technologies Test', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (374, N'PriceBusterDVD_NZ_BN', N'Pricebuster NZ BNZ', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (389, N'TAirNewZealandNZ_All', N'Test Air NZ - All', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (390, N'T6400061', N'The Warehouse Test', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (392, N'T6400246', N'University of Waikato Test', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (538, N'T6400449', N'NZTA Payments Dev System Testing', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (544, N'T6400447', N'NZTA Tolling Dev System Testing', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (631, N'SS64000475', N'Smeedi Test', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (729, N'T6400048', N'Marram Community Trust Test', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (776, N'SS64000665', N'POLi Test Bench', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (936, N'T6400002', N'WorldRemit Test NZ', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (1033, N'SS64005103', N'Ahura Consulting Limited', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (1173, N'SS64005386', N'Warehouse Stationery Test', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (1236, N'SS64005423', N'KlickEx Test', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (1435, N'T6400477', N'NZMCA', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (1580, N'T6400478', N'2 Degrees Mobile - Test', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (1626, N'SS64006121', N'Property Council New Zealand', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (1714, N'SS64006558', N'ServiceFinder.co.nz', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (1972, N'T6400480', N'2 Degrees Mobile Accept Test', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (1988, N'T6400484', N'HelloClub Test', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (2011, N'T6400482', N'Horowhenua District Council Test', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (2260, N'SS64008067', N'Success Global', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (2274, N'64007479', N'Samsung Electronics New Zealand', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (2397, N'SS64008228', N'MyBitcoinSaver.com', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (2418, N'6400478', N'Spark Staging', N'T')
GO
INSERT [dbo].[merchant_t] ([id], [merchant_num], [merchant_nm], [status]) VALUES (2441, N'SS64008239', N'Kiwi Petz', N'T')
GO
SET IDENTITY_INSERT [dbo].[merchant_t] OFF
GO
SET IDENTITY_INSERT [dbo].[transaction_t] ON 
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215957, 389, CAST(N'2020-04-01T06:55:37.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215958, 389, CAST(N'2020-04-01T06:56:13.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215959, 389, CAST(N'2020-04-01T07:06:47.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215960, 389, CAST(N'2020-04-01T07:09:09.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215961, 389, CAST(N'2020-04-01T08:19:28.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215962, 389, CAST(N'2020-04-01T08:19:45.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215963, 389, CAST(N'2020-04-01T08:19:57.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215964, 389, CAST(N'2020-04-01T08:20:16.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215965, 389, CAST(N'2020-04-01T09:33:40.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215966, 389, CAST(N'2020-04-01T09:33:46.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215967, 389, CAST(N'2020-04-01T11:05:35.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215968, 389, CAST(N'2020-04-01T11:06:13.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215969, 389, CAST(N'2020-04-01T11:12:51.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215970, 389, CAST(N'2020-04-01T11:17:38.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215971, 389, CAST(N'2020-04-01T12:45:13.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215972, 389, CAST(N'2020-04-01T12:45:49.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215973, 389, CAST(N'2020-04-01T12:50:17.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18201776, 1580, CAST(N'2020-04-01T14:16:38.000' AS DateTime), 0, N'ANZ')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215974, 389, CAST(N'2020-04-01T12:59:06.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215975, 389, CAST(N'2020-04-01T14:18:13.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215976, 389, CAST(N'2020-04-01T14:18:21.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215977, 389, CAST(N'2020-04-01T14:26:15.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215978, 389, CAST(N'2020-04-01T14:33:02.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215979, 389, CAST(N'2020-04-01T15:12:43.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215980, 389, CAST(N'2020-04-01T15:12:46.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215981, 389, CAST(N'2020-04-01T15:41:14.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18215982, 389, CAST(N'2020-04-01T15:43:53.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18223719, 2441, CAST(N'2020-04-02T10:20:03.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18231457, 389, CAST(N'2020-04-02T07:11:32.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18231458, 389, CAST(N'2020-04-02T07:13:06.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18231459, 389, CAST(N'2020-04-02T08:49:33.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18231460, 389, CAST(N'2020-04-02T09:03:17.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18231461, 389, CAST(N'2020-04-02T09:08:39.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18231462, 389, CAST(N'2020-04-02T11:17:25.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18231463, 389, CAST(N'2020-04-02T11:20:53.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18231464, 389, CAST(N'2020-04-02T11:22:38.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18231465, 389, CAST(N'2020-04-02T12:03:20.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18231466, 389, CAST(N'2020-04-02T12:03:58.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18231467, 389, CAST(N'2020-04-02T12:20:27.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18231468, 389, CAST(N'2020-04-02T12:37:47.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18233881, 341, CAST(N'2020-04-02T13:54:30.000' AS DateTime), 0, N'ANZ')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18237848, 2011, CAST(N'2020-04-03T13:31:36.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18245130, 389, CAST(N'2020-04-03T06:24:34.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18245131, 389, CAST(N'2020-04-03T06:26:47.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18245132, 389, CAST(N'2020-04-03T10:55:09.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18245133, 389, CAST(N'2020-04-03T11:00:42.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18245134, 389, CAST(N'2020-04-03T11:00:57.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18245135, 389, CAST(N'2020-04-03T14:01:58.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18245136, 389, CAST(N'2020-04-03T14:08:48.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18245137, 389, CAST(N'2020-04-03T14:41:57.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18245138, 389, CAST(N'2020-04-03T14:44:40.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18250367, 2441, CAST(N'2020-04-04T09:53:19.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18274546, 2274, CAST(N'2020-04-06T02:50:01.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18274563, 1714, CAST(N'2020-04-06T06:36:45.000' AS DateTime), 1, N'ANZ')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18277532, 389, CAST(N'2020-04-06T06:37:57.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18277533, 389, CAST(N'2020-04-06T06:46:45.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18277534, 389, CAST(N'2020-04-06T07:36:29.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18277535, 389, CAST(N'2020-04-06T07:43:00.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18277536, 389, CAST(N'2020-04-06T08:11:22.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18277537, 389, CAST(N'2020-04-06T08:12:13.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18279767, 341, CAST(N'2020-04-06T09:40:12.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18268407, 1033, CAST(N'2020-04-06T20:15:56.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18270264, 544, CAST(N'2020-04-06T12:36:12.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18270265, 544, CAST(N'2020-04-06T12:37:11.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18270266, 544, CAST(N'2020-04-06T12:38:08.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18270267, 544, CAST(N'2020-04-06T12:40:05.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18270268, 544, CAST(N'2020-04-06T12:42:50.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18270269, 544, CAST(N'2020-04-06T12:43:36.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18270270, 544, CAST(N'2020-04-06T12:45:09.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18270271, 544, CAST(N'2020-04-06T12:45:26.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18273055, 538, CAST(N'2020-04-06T12:34:02.000' AS DateTime), 0, N'IBA')
GO
INSERT [dbo].[transaction_t] ([id], [merchant_id], [transaction_dt], [trans_live], [bank_txt]) VALUES (18277538, 389, CAST(N'2020-04-06T11:30:42

Answer 1

Vla*_*nov 2

在您的第一个查询中，您有这个子句：

GROUP BY me.id, me.merchant_num, me.merchant_nm, me.status

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在你的第二个查询中，你有这个子句：

GROUP BY me.id, me.merchant_num, me.merchant_nm, me.status, tt.bank_txt

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您在第二个查询中获得不同的行数，因为您的行GROUP BY数不同。你需要保持不变。

这是一种方法。我使用 CTE 使查询可读。

正如您在查询的注释中看到的，它返回trans_live商家最近交易的列值。商家在所有日期的最新交易，无论 CTE 中的过滤器如何。与使用 IBank (IBA) 的最后一笔交易的日期相同。无论 CTE 中的过滤器如何，它都会返回商家在所有日期中的最后一笔交易。

不过，从问题中尚不清楚这是否是您想要的。请澄清。

WITH
CTE_Merchants
AS
(
    SELECT -- distinct
        -- you don't need distinct here, because GROUP BY does it
        -- try to comment out distinct, you should get exactly the same result
        me.id, me.merchant_num, me.merchant_nm
        ,count(tt.id) as num_transactions
        -- return 0 count for merchants that don't have any transactions
        -- within the given range of dates

        ,CASE WHEN me.status = 'A' THEN 'Yes' ELSE 'No' END as production_mode
    FROM
        merchant_t me
        LEFT OUTER JOIN transaction_t tt
            ON  tt.merchant_id = me.id 
            AND tt.transaction_dt BETWEEN '2020-04-01' and '2020-04-30'
    WHERE me.status = 'T'
    GROUP BY me.id, me.merchant_num, me.merchant_nm, me.status
)
SELECT
    CTE_Merchants.id
    ,CTE_Merchants.merchant_num
    ,CTE_Merchants.merchant_nm
    ,CTE_Merchants.num_transactions
    ,CTE_Merchants.production_mode
    ,A1.is_live
    ,A2.last_IBA_transaction_dt
FROM
    CTE_Merchants
    OUTER APPLY
    (
        -- use OUTER APPLY (not CROSS APPLY) in case there are merchants with no transactions
        -- The value of the "trans_live" column for the merchant's most recent transaction.
        -- Most recent across all dates, regardless of the filter in the CTE
        select top 1
            transaction_t.trans_live AS is_live
        from transaction_t
        where
            transaction_t.merchant_id = CTE_Merchants.id
        order by transaction_dt desc
    ) AS A1
    OUTER APPLY
    (
        -- use OUTER APPLY (not CROSS APPLY) in case there are merchants with no transactions
        -- The date of the last transaction that uses IBank (IBA).
        -- The last transaction across all dates, regardless of the filter in the CTE
        select top 1
            transaction_t.transaction_dt AS last_IBA_transaction_dt
        from transaction_t
        where
            transaction_t.merchant_id = CTE_Merchants.id
            and transaction_t.bank_txt = 'IBA'
        order by transaction_dt desc
    ) AS A2
;

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为了使该查询高效工作，我建议创建某些索引。IX_status您已经在表上有了一个索引merchant_t。这很好。

表上的那些索引transaction_t对于此类查询来说并不是最好的。您现有的索引IX_transaction_dt, IX_trans_live,IX_bank_txt对于此查询没有用处。即使IX_merchant_id它本身也不是很有用，特别是如果您将其替换为上的复合索引(merchant_id, transaction_dt)，如下所示。

id我希望您在表中确实有一个聚集主键transaction_t。类似于merchant_t表中的主键。如果没有，我会创建它。

然后，为了在merchant_t和transaction_t表之间进行有效连接并有效检索最新数据，trans_live我们需要以下索引：

CREATE NONCLUSTERED INDEX [IX_merchant_id_transaction_dt] ON [dbo].[transaction_t]
(
    merchant_id,
    transaction_dt -- you can put DESC here, but it should not matter
) INCLUDE (trans_live)

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该索引中的列顺序很重要。

您刚刚有一个索引transaction_dt。该查询可能会使用它，但它的效率不如 on (merchant_id, transaction_dt)。如果您有按交易日期过滤的查询而不查看merchant_id. 如果你没有这样的疑问，你最好放弃它。“以防万一”拥有太多索引可能会给优化器带来问题，并且会减慢更新和插入速度。

为了有效检索最后一个，last_IBA_transaction_dt我们需要这个索引：

CREATE NONCLUSTERED INDEX [IX_merchant_id_bank_txt_transaction_dt] ON [dbo].[transaction_t]
(
    merchant_id,
    bank_txt,
    transaction_dt -- you can put DESC here, but it should not matter
)

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同样，该索引中的列顺序很重要。

如果您不想专门为此查询创建两个索引，则可以尝试仅使用一个索引，这对于获取非常有用，trans_live并且应该对last_IBA_transaction_dt.

CREATE NONCLUSTERED INDEX [IX3] ON [dbo].[transaction_t]
(
    merchant_id,
    transaction_dt DESC
) INCLUDE (trans_live, bank_txt)

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您可以尝试使用前两个指标来衡量性能，然后仅使用第三个指标来进行比较。

顺便说一句，如果有商家在给定的日期范围内没有任何交易，那么查询将为这些商家返回一行。您原始查询COUNT中的将为这些商家返回1。也许这不是你想要的。

要返回0这些商家的计数，该COUNT函数应该是COUNT(tt.id)。我在上面的代码中进行了这些更改。

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