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Show records based on prior records

Hello:

I have this table

PersonName        DateA             DateB
Bill              01-09-2014        01-29-2014
Bill              01-09-2014        01-16-2014
Bill              01-09-2014        02-24-2014
John            01-09-2014        02-16-2014
John            01-09-2014        01-29-2014
John            01-09-2014        03-08-2014

What I want to do is select all records by a date like the SQL statement below

SELECT PersonName, DateA, DateB where DateB = '01-29-2014'

However, if there is a record with an earlier date, I do not want that record to be shown. So using the table above only this record should show.

John            01-09-2014        01-29-2014
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RecipeDan
Asked:
RecipeDan
1 Solution
 
lcohanDatabase AnalystCommented:
you will need to use a MAX or TOP 1 and GROUP BY structure in your SQL statement.

{edit ValentinoV: links to competing site removed}
0
 
Surendra NathTechnology LeadCommented:
you can write it with a not exists clause as shown below

SELECT PersonName, DateA, DateB
FROM <Your Table> as T1 
where DateB = '01-29-2014'
WHERE NOT EXISTS ( SELECT 1 FROM <your Table> as T2 where T2.DateB < T1.DateB) 

Open in new window


In the above code replace<your Table> with your table Name.
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Dan CraciunIT ConsultantCommented:
I don't get it.

According to what you wrote, that query should give you 2 results:

Bill              01-09-2014        01-29-2014
John            01-09-2014        01-29-2014

Why is the "Bill" row not an acceptable result?
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RecipeDanAuthor Commented:
Here is a code I came with. Are there any downsides or potential errors?
SELECT RowNumber, PersonName, DateA, DateB
FROM
(
SELECT ROW_NUMBER() OVER(PARTITION BY PersonName ORDER BY DateB ASC) RowNumber, PersonName, DateA, DateB
FROM            DataTest
)
table1
where DateB='01-29-2014' and RowNumber='1'

Open in new window

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smiliefaceCommented:
Try this. You'll need to substitute your table name for #PersonTable

WITH CTE_PersonTable AS (
   SELECT 
         PersonName
      FROM #PersonTable
      WHERE DateB <  CONVERT(DATE, '01-29-2014', 101)
      GROUP BY PersonName
   )
SELECT 
   *
   FROM #PersonTable
   LEFT OUTER JOIN CTE_PersonTable
      ON CTE_PersonTable.PersonName = #PersonTable.PersonName
   WHERE DateB = CONVERT(DATE, '01-29-2014', 101)
   AND   CTE_PersonTable.PersonName IS NULL

Open in new window

0
 
Ephraim WangoyaCommented:
I suppose its just the way you phrased your question that was a bit confusing but your query should work ok
0
 
Surendra NathTechnology LeadCommented:
did you give this a try
SELECT PersonName, DateA, DateB
FROM <Your Table> as T1 
where DateB = '01-29-2014'
WHERE NOT EXISTS ( SELECT 1 FROM <your Table> as T2 where T2.DateB < T1.DateB) 

Open in new window


as described here http://www.experts-exchange.com/Microsoft/Development/MS-SQL-Server/Q_28355426.html#a39830974
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RecipeDanAuthor Commented:
Hi Surendra:

Yes I did try it. But it does not show any results.
SELECT PersonName, DateA, DateB
FROM DataTest as T1 
WHERE NOT EXISTS ( SELECT 1 FROM DataTest as T2 where T2.DateB < T1.DateB) AND DateB='2014-01-29'

Open in new window

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Surendra NathTechnology LeadCommented:
Oops there is one join condition that is missing over there corrected the same check the below one

declare @t table 
(
 PersonName VARCHAR(20), dateA DATETIME, DateB DATETIME
)
INSERT INTO @T VALUES ('Bill',              '01-09-2014',        '01-29-2014')
INSERT INTO @T VALUES ('Bill',              '01-09-2014',        '01-16-2014')
INSERT INTO @T VALUES ('Bill',              '01-09-2014',        '02-24-2014')

INSERT INTO @T VALUES ('John',              '01-09-2014',        '02-16-2014')
INSERT INTO @T VALUES ('John',              '01-09-2014',        '01-29-2014')
INSERT INTO @T VALUES ('John',              '01-09-2014',        '03-08-2014')

SELECT T1.*
FROM @T as T1 
where T1.DateB = '01-29-2014'
AND EXISTS ( SELECT 1 FROM @T as T2 where T2.DateB < T1.DateB and T1.PersonName = T2.PersonName) 

Open in new window


the @T table is created to check the validation of the statement, replace it with your own table.
0
 
RecipeDanAuthor Commented:
Yes it works. However, I had to change T2.DateB < T1.DateB to T2.DateB > T1.DateB. Thank you for your assistance.
0
 
Surendra NathTechnology LeadCommented:
oops my mistake... actually it should be some thing like below

declare @t table 
(
 PersonName VARCHAR(20), dateA DATETIME, DateB DATETIME
)
INSERT INTO @T VALUES ('Bill',              '01-09-2014',        '01-29-2014')
INSERT INTO @T VALUES ('Bill',              '01-09-2014',        '01-16-2014')
INSERT INTO @T VALUES ('Bill',              '01-09-2014',        '02-24-2014')

INSERT INTO @T VALUES ('John',              '01-09-2014',        '02-16-2014')
INSERT INTO @T VALUES ('John',              '01-09-2014',        '01-29-2014')
INSERT INTO @T VALUES ('John',              '01-09-2014',        '03-08-2014')

SELECT T1.*
FROM @T as T1 
where T1.DateB = '01-29-2014'
AND NOT EXISTS ( SELECT 1 FROM @T as T2 where T2.DateB < T1.DateB and T1.PersonName = T2.PersonName) 

Open in new window

0
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