sql get max date from difrent columns

Question

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hi want to retrieve max date from multiple column
say
i have column

a1|a2|a3|a4|b1|b2|b3|b4

all these are column now what i want is i want to get the latest date
from a1|a2|a3|a4

and |b1|b2|b3|b4 there ar more columns c1......,d1,e1.........so sone just for the sake of simplicity
i have mention two series
so far i have written

SQL

Select 
   
  MAX(HepatitisBDate.im_HepatitisBDate1)  as 'iHepatitisBDate1'

   from
   ( 
Select CONVERT(DATE,ISNULL(im_HepatitisBDate1 , CONVERT(DATE,'01/01/1800',103)),103)as im_HepatitisBDate1 from md_Immunization 
Union 
Select CONVERT(DATE,ISNULL(im_HepatitisBDate2 , CONVERT(DATE,'01/01/1800',103)),103)as im_HepatitisBDate1 from md_Immunization 
Union 
Select CONVERT(DATE,ISNULL(im_HepatitisBDate3 , CONVERT(DATE,'01/01/1800',103)),103)as im_HepatitisBDate1 from md_Immunization 
Union 
Select CONVERT(DATE,ISNULL(im_HepatitisBDate4 , CONVERT(DATE,'01/01/1800',103)),103)as im_HepatitisBDate1 from md_Immunization 
) as HepatitisBDate

Posted 23-Sep-13 20:18pm

rocky_em

Updated 23-Sep-13 20:29pm

Aarti Meswania

v2

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Maciej Los · Accepted Answer · 2013-09-23T23:13:00

Solution 1 (using TOP, MAX[^] and UNPIVOT[^])

SQL

SELECT TOP(1) FieldName, MAX(DateValue) AS MaxDate
FROM (
    SELECT FieldName, DateValue
    FROM (
        SELECT a1, a2, a3, a4, b1, b2, b3, b4
        FROM TableName
        ) AS pvt
    UNPIVOT (DateValue FOR FieldName IN(a1, a2, a3, a4, b1, b2, b3, b4)) AS unpvt
    ) AS T
GROUP BY FieldName
ORDER BY DateValue DESC

Solution 2 (using RANK[^] and UNPIVOT[^])

SQL

--DROP TABLE #Integers

CREATE TABLE #Integers (a1 INT, a2 INT, a3 INT, a4 INT,
                        b1 INT, b2 INT, b3 INT, b4 INT,
                        c1 INT, c2 INT, c3 INT, c4 INT)

INSERT INTO #Integers (a1, a2, a3, a4,
                        b1, b2, b3, b4,
                        c1, c2, c3, c4)
SELECT 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12
UNION ALL SELECT 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1
UNION ALL SELECT 8, 5, 2, 7, 4, 1, 9, 6, 3, 1, 2, 3
UNION ALL SELECT 3, 6, 9, 1, 4, 7, 2, 5, 8, 9, 8, 7

SELECT FieldName, FieldValue
FROM (
    SELECT FieldName, FieldValue, RANK() OVER(ORDER BY FieldValue DESC) AS [Rank]
    FROM (
        SELECT *
        FROM #Integers
    ) AS pvt
    UNPIVOT (FieldValue FOR FieldName IN(a1, a2, a3, a4,
                                        b1, b2, b3, b4,
                                        c1, c2, c3, c4)) AS unpvt
) AS T
WHERE [Rank]=1

DROP TABLE #Integers

Suresh Suthar · Accepted Answer · 2013-09-23T21:17:00

Solution 1

I think this can solve your problem
http://stackoverflow.com/a/1398019/599560[^]

Posted 23-Sep-13 21:17pm

Suresh Suthar