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Identify when you have reached the last record on a SQL Cursor

Posted on 2010-08-23
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Last Modified: 2012-08-14
Is there anyway to identify when you have reached the last record in a SQL Cursor. I need to manipulate the data within a cusor, but the first and last records need particular data manipulation carried out on them.

Doing this on the first record is relatively straight forward. I am not aware of and EOF property I can check for cursors as you can do in recordsets, does anyone know of a simple way of doing this?

Nathan
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Question by:NathanIrwin
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9 Comments
 
LVL 11

Expert Comment

by:Larissa T
ID: 33507665
this is Fetch syntax.
FETCH
          [ [ NEXT | PRIOR | FIRST | LAST
                    | ABSOLUTE { n | @nvar }
                    | RELATIVE { n | @nvar }
               ]
               FROM
          ]
{ { [ GLOBAL ] cursor_name } | @cursor_variable_name }
[ INTO @variable_name [ ,...n ] ]
.....
LAST
Returns the last row in the cursor and makes it the current row

http://msdn.microsoft.com/en-us/library/ms180152.aspx
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Accepted Solution

by:
cyberkiwi earned 500 total points
ID: 33507686
You could try @@CURSOR_ROWS
http://msdn.microsoft.com/en-us/library/ms176044.aspx

Or declare the cursor as STATIC, e.g.

declare c cursor static for ....

And go forward to test
 fetch next from c into @var
 if @@fetch_status = -1
    -- we are on last record
 else
    -- we are not
 fetch prior from c into @var  -- go back to proper location

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Expert Comment

by:infolurk
ID: 33507687
Its only possible if you have an incrementing field that you can select the max or top value from. Data is not stored in any particular order in SQL tables.
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LVL 2

Expert Comment

by:rajeshprasath
ID: 33507726
the following code will help you to achieve your requirement,

FETCH
 [ [ NEXT | PRIOR | FIRST | LAST
 | ABSOLUTE { n | @nvar }
 | RELATIVE { n | @nvar }
 ]
 FROM
 ]
 { { [ GLOBAL ] cursor_name } | @cursor_variable_name }
 [ INTO @variable_name [ ,...n ] ]

refer this code also

DECLARE @name varchar(100)
DECLARE @dbId Int

DECLARE sample_cursor SCROLL CURSOR FOR select name, database_id from sys.databases

OPEN sample_cursor

FETCH FIRST FROM sample_cursor INTO @name, @dbId
print @name
print @dbId
print '-----'

FETCH LAST FROM sample_cursor INTO  @name, @dbId
print @name
print @dbId
print '-----'

CLOSE sample_cursor
DEALLOCATE sample_cursor

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LVL 2

Expert Comment

by:rajeshprasath
ID: 33507735
you need to declare your cursor as SCROLL CURSOR, then only this will work.
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Expert Comment

by:dteshome
ID: 33507755
... according to the definition, LAST, returns the last row in the cursor and makes it the current row.
So, if you must process the records sequentially (not make last, current)  you can use the SELECT  statement used in the cursor declaration and do "SELECT Count(*) ..."  this will give the # of records that will be generated when the cursor is declared.  Once you have this value, declare an int variable, set it to the count, @MaxRecs. Also declare an int varoiable to keep track of the current count, @Count. Then, inside the while loop, check to see if @count = @MaxRecs, if so it is the last rec, process accordingly.  If not, increment @count process fetched rec etc ...
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LVL 58

Assisted Solution

by:cyberkiwi
cyberkiwi earned 500 total points
ID: 33507770
Rajesh,

STATIC works as well, among others, as shown in 2nd comment to the question.

A more detailed skeleton provided below.
With STATIC, you can also use @@CURSOR_ROWS (see link in 2nd comment above) without having to run a separate COUNT query.
declare @islast = 0
declare c cursor STATIC for ....
open c
fetch next from c into @var
while @@fetch_status = 0 begin
 -- test if we are on the last row
 fetch next from c into @var
 set @islast = case when @@fetch_status = -1 then 1 else 0 end
 fetch prior from c into @var  -- go back to proper location

 if @islast = 1 then ......

  -- rest of code

 fetch next from c into @var
end

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LVL 7

Author Comment

by:NathanIrwin
ID: 33507834
Thanks for the quick responses, I will try some of these and get back to you
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LVL 7

Author Closing Comment

by:NathanIrwin
ID: 33507903
Thanks cyberkiwi.
I basically used a combination of you answers:
basically....

WHILE (@@FETCH_STATUS =0)
   modify first record
   FETCH NEXT
   modify the rest of the records
IF (@@FETCH_STATUS =-1)
   modify last record
END
END

Cheers
Nathan
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