MySQL to Oracle Syntax Error (Limit / Offset / Update)

I have a MySQL query that works on my current MySQL database. I've been forced to move over to oracle, so I'm trying to port all my stored procedures / programs to use the Oracle SQL Syntax. I'm having a lot of trouble on one particular query. Here is the MySQL query. It updates a table using a subquery.

 update table1 alf 
 set nextcontractid = 
 (
 select 
    contractid from table1copy alf2 
 where 
    alf2.assetid = alf.AssetID 
 and 
    alf2.lasttradedate > alf.LastTradeDate 
 order by lasttradedate asc limit 1
 ) 
 where complete = 0

In oracle, I c开发者_C百科an't use the the limit command, so I've looked for the workaround. Here is my oracle query. (which doesn't work.)

 update table1 alf
 set nextcontractid = 
   (select contractid from
     (
     SELECT contractid, rownum as row_number
     FROM table1copy alf2
     WHERE alf2.assetid     = alf.assetid
     AND alf2.lasttradedate > alf.lasttradedate
     ORDER BY lasttradedate ASC
   ) 
   where row_number = 1)
 where alf.complete = 0

I get the following error:

 Error at Command Line:8 Column:29
 Error report:
 SQL Error: ORA-00904: "ALF"."LASTTRADEDATE": invalid identifier
 00904. 00000 -  "%s: invalid identifier"

line 8 is:

 AND alf2.lasttradedate > alf.lasttradedate

Removing the update statement and putting in some dummy values into the subquery yields the correct results for the subquery:

   (select contractid from 
     ( 
     SELECT contractid, rownum as row_number 
     FROM asset_list_futures_copy alf2 
     WHERE alf2.assetid     = 'GOLD' 
     AND alf2.lasttradedate > '20110101' 
     ORDER BY lasttradedate ASC 
     )  
    where row_number = 1)

Looking at the error, it looks like the second reference to alf isn't working. Any idea how I can change my query so that it works in oracle?

Seems the parser does not like that, despite the fact it is sintacticaly correct. Probably the two imbricated and ordered clause is blinding him somehow. I reproduced that.

You can use an analytical function:

update table1 alf
 set nextcontractid = 
     (SELECT min(contractid) keep (dense_rank first order by lasttradedate asc) 
     FROM table1copy alf2
     WHERE alf2.assetid     = alf.assetid
     AND alf2.lasttradedate > alf.lasttradedate
     )
 where alf.complete = 0

You can use WHERE rownum = 1, or rownum BETWEEN x AND y in cases that you want more results.