Talk:Cursor (databases)

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I presume that there must be some pros with cursors as well? Senappp 21:50, 1 January 2006 (UTC)[reply]

Yeah, there are. This article is in pretty poor shape, and I mean to add to it. Time is the limiter, as usual. -- Mikeblas 21:59, 1 January 2006 (UTC)[reply]

I'm finally getting 'round to this, so please be patient in the interim. -- Mikeblas 00:35, 7 June 2006 (UTC)[reply]

Great! -- Patrickdepinguin 20:37, 9 June 2006 (UTC)[reply]

Of course there are, or they wouldn't have been invented in the first place. There are (limited) situations where they make the difference between something being possible or impossible. Which is a pretty compelling advantage in my book. I've already begun improving the article, but will attempt to address this and include a real-world example or two. DigitalEnthusiast 00:54, 15 December 2006 (UTC)[reply]

I believe that the "disadvantages" section is partly wrong and partly very imprecise. First, cursors are the only way to transfer data from a relational DBMS to a procedural application (with the exception being a SELECT INTO statement). Next, a FETCH does not imply a network round-trip at all - the DBMS client can use block fetch. Also, what are those "restrictions on SELECT statements" and what is the complex syntax? Examples would be important! After all, declaring a cursor is just prefixing a SELECT statement with DECLARE cursor-name CURSOR FOR statement. Finally, I believe that system-specific things like SQL Server's implementation based on temp tables should go into a separate (sub)section. --Stolze 13:46, 20 December 2006 (UTC)[reply]

I'm actually not aware of any restrictions on the SELECT statement; however cursors are not the only way to get data from the db engine to the client app - the DataReader class in .net parses a TDS or Oracle network stream directly as it's sent up. As for the "complex syntax," I think that's showing up because most people who've used SQL are used to set-based operations, and not procedural coding. DigitalEnthusiast 20:58, 20 December 2006 (UTC)[reply]

A description of the differences between the five types of cursors would be helpful. --Sapphire Wyvern 03:13, 6 September 2006 (UTC)[reply]

The most current SQL standard SQL:2003 does not know the concept of multi-row fetch. Subclause 14.3, "<fetch statement>" has this BNF:

 <fetch statement> ::=
   FETCH [ [ <fetch orientation> ] FROM ] <cursor name> INTO <fetch target list>
 
 <fetch orientation> ::=
     NEXT
   | PRIOR
   | FIRST
   | LAST
   | { ABSOLUTE | RELATIVE } <simple value specification>
 
 <fetch target list> ::=
   <target specification> [ { <comma> <target specification> }... ]

No multi-row stuff here. So I removed this again. --Stolze 15:23, 26 March 2007 (UTC)[reply]

How to add parameters in a cursor, take is an example:

CURSOR c_employee (p_dept VARACHAR2) IS

 SELECT   name,salary  
 FROM   t_employee
 WHERE   deptno=p_dept;

--Billbinshi (talk) 06:15, 19 August 2008 (UTC)Bill.Shi[reply]

Probably not worthy of trivia, but I had a boss who said this once, and he wasn't very creative, leading me to think someone told him ... DigitalEnthusiast 19:55, 21 December 2006 (UTC)[reply]

Nice one —Preceding unsigned comment added by

syntax: declare

cursor c1 is
  select statement
  where condition;
variables datatype;

begin

open c1;
fetch c1 into variables;
exit when c1%notfound;
  do something with the data;
end loop;
close c1;

end;

guideline: Always, use 'exit when c1%notfound' soon after the "fetch cursor" statement to avoid the duplication of the last record of the cursor.

Abhijithdev (talk) 05:56, 8 July 2011 (UTC)[reply]