Oracle-L: Re: SQL Query Help

From: Mark Richard <mrichard_at_transurban.com.au>
Date: Wed, 28 May 2003 19:39:43 -0800
Message-ID: <F001.005A520D.20030528193943@fatcity.com>

This latest alternative will clearly only work when the latest id is known - I doubt this is reality.

There was a mention that the actual query is more complex - without seeing that complexity it's hard to offer further advice. RWB has provided the correct approach normally taken. If the date is indexed then Oracle can determine the max date very easily - the query looks worse than reality.

Another approach (which is normally worse though) is to order the query by date then wrap a "select * from (inner_query} where rownum = 1" around it. It's clunky though and probably isn't what you are after.

                                                                                                                                      
                      "Daniel W. Fink"                                                                                                
                      <optimaldba_at_yahoo        To:       Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>                  
                      .com>                    cc:                                                                                    
                      Sent by:                 Subject:  Re: SQL Query Help                                                           
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                      29/05/2003 12:54                                                                                                
                      Please respond to                                                                                               
                      ORACLE-L

SELECT ID,MAX(LastModDate)
FROM Tab
where id = 1
group by ID;

--
Daniel W. Fink
http://www.optimaldba.com


Basavaraja, Ravindra wrote:



>I had tried this as per Oracle Metalink Note.When I add the group by ID it

will display both the records like


>2           1/20/2003 2:56:18 AM

>1           4/23/2003 10:26:42 PM

>

>but I want to see the only the record with the latest time stamp like

>1           4/23/2003 10:26:42 PM

>

>-----Original Message-----

>Sent: Wednesday, May 28, 2003 6:25 PM

>To: Multiple recipients of list ORACLE-L

>

>

>Add "group by ID;" as in:

>

>

>SELECT ID,MAX(LastModDate) FROM  Tab

>group by ID;

>

>

>

>>-----Original Message-----

>>From: Basavaraja, Ravindra [mailto:Ravindra.Basavaraja_at_T-Mobile.com]

>>Sent: Wednesday, May 28, 2003 8:15 PM

>>To: Multiple recipients of list ORACLE-L

>>Subject: SQL Query Help

>>

>>

>>i have a query that returns 2 rows with one column being id

>>and the other

>>being date-time stamp.

>>

>>i want to select the row with the latest timestamp among those two

>>records.they have difference id values

>>

>>SELECT ID,LastModDate

>>FROM  Tab

>>

>>ID         LastModDate

>>--         -----------

>>2          1/20/2003 2:56:18 AM

>>1          4/23/2003 10:26:42 PM

>>

>>I want to modify the above query to return the row with id=1

>>which has the

>>latest timestamp

>>

>>I tried this

>>

>>SELECT ID,MAX(LastModDate)

>>FROM  Tab

>>

>>getting this error

>>OERR: ORA 937 not a single-group group function

>>

>>how do i get this work.

>>

>>Thanks

>>

>>

>>



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Author: Daniel W. Fink
  INET: optimaldba_at_yahoo.com

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-- 
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-- 
Author: Mark Richard
  INET: mrichard_at_transurban.com.au

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Received on Wed May 28 2003 - 22:39:43 CDT