SQL - Getting Most Recent Date From Multiple Columns - sql

Question

Assume a rowset containing the following
EntryID Name DateModified DateDeleted
-----------------------------------------------
1 Name1 1/2/2003 NULL
2 Name1 1/3/2005 1/5/2008
3 Name1 1/3/2006 NULL
4 Name1 NULL NULL
5 Name1 3/5/2008 NULL
Clarification:
I need a single value - the largest non-null date from BOTH columns. So the largest of all ten cells in this case.

Answer 1

SELECT MAX(CASE WHEN (DateDeleted IS NULL OR DateModified > DateDeleted)
THEN DateModified ELSE DateDeleted END) AS MaxDate
FROM Table

Answer 2

For MySQL, Postgres or Oracle, use the GREATEST function:
SELECT GREATEST(ISNULL(t.datemodified, '1900-01-01 00:00:00'),
ISNULL(t.datedeleted, '1900-01-01 00:00:00'))
FROM TABLE t
Both Oracle and MySQL will return NULL if a NULL is provided. The example uses MySQL null handling - update accordingly for the appropriate database.
A database agnostic alternative is:
SELECT z.entryid,
MAX(z.dt)
FROM (SELECT x.entryid,
x.datemodified AS dt
FROM TABLE x
UNION ALL
SELECT y.entryid
y.datedeleted AS dt
FROM TABLE y) z
GROUP BY z.entryid

Answer 3

As a general solution, you could try something like this:
select max(date_col)
from(
select max(date_col1) AS date_col from some_table
union
select max(date_col2) AS date_col from some_table
union
select max(date_col3) AS date_col from some_table
...
)
There might be easier ways, depending on what database you're using.

Answer 4

How about;
SELECT MAX(MX) FROM (
SELECT MAX(DateModified) AS MX FROM Tbl
UNION
SELECT MAX(DateDeleted) FROM Tbl
) T

Answer 5

The answer depends on what you really want. If you simply want the most recent of the two date values then you can do:
Select Max(DateModified), Max(DateDeleted)
From Table
If you are asking for the largest value from either column, then you can simply do:
Select Case
When Max(DateModified) > Max(DateDeleted) Then Max(DateModified)
Else Max(DateDeleted)
End As MaxOfEitherValue
From Table

Answer 6

The above are all valid answers;
But I'm Not sure if this would work?
select IsNull((
select MAX(DateModified)
from table
)
,
(
select MAX(DateDeleted)
from table
)
) as MaxOfEitherValue
from table
Edit 1:
Whilst in the shower this morning, I had another solution:
Solution 2:
select MAX(v) from (
select MAX(DateModified) as v from table
union all
select MAX(DateDeleted) as v from table
) as SubTable
Edit 3:
Damn it, just spotted this is the same solution as Alex k. sigh...

Answer 7

How to find the Latest Date from the columns from Multiple tables
e.g. if the Firstname is in Table1, Address is in Table2, Phone is in Table3:
When you are using with main SELECT statement while selecting other columns it is best written as :
SELECT Firstname
,Lastname
,Address
,PhoneNumber
,
,(SELECT max(T.date_col) from(select max(date_col1) AS date_col from Table1 Where ..
union
select max(date_col2) AS date_col from Table2 Where..
union
select max(date_col3) AS date_col from Table3 Where..
) AS T
) AS Last_Updated_Date
FROM Table T1
LEFT JOIN Table T2 ON T1.Common_Column=T2.Common_Column
LEFTJOIN Table T3 ON T1.Common_Column=T3.Common_Column