Re: Cursor Issue??

# bradbudge(at)hotmail(dot)com / 2005-08-02 10:01:34 -0400:
> I made it happen in MicrosoftSQL using the first code below. The only
> difference is I had to create variables. Which I'm having a hard time
> trying to replicate it in psql.
>
> __________Microsoft Code___________
> USE test
> GO
> DECLARE @qty INT, @Length varchar(20), @Width varchar(40)
> DECLARE cursor1 SCROLL CURSOR FOR
> SELECT * from Parts
> OPEN cursor1
> FETCH FIRST FROM cursor1
> INTO @qty, @Length, @Width
> INSERT INTO PartsTemp (qty, Length, Width)
> VALUES (@qty, @Length, @Width)
> CLOSE cursor1
> DEALLOCATE cursor1
> GO

The code above puts a single, randomly chosen tuple from Parts into
PartsTemp. If that's all you need, you can do it with:

INSERT INTO PartsTemp (SELECT * FROM Parts LIMIT 1);

> __________psql Code___________
> (These declaration of vaiables don't work)
> DECLARE c_qty INT;
> DECLARE c_Length FLOAT;
> DECLARE c_Width FLOAT;
>
> BEGIN;
> DECLARE cursor1 CURSOR FOR SELECT * FROM Parts;
> FETCH FIRST FROM cursor1 INTO c_qty, c_Length, c_Width;
> INSERT INTO partstemp VALUES (c_qty, c_Length, c_Width);
> CLOSE cursor1;
> COMMIT;
>
> Got any ideas using variable to transfer singular rows?

If you need to do more (you aren't telling much), and want/need to
use cursors, you'll have to resort to using PL/pgSQL. This hack
would do it:

CREATE TABLE t1 (t1i INT, t1c CHAR(1));
CREATE TABLE t2 (t2i INT, t2c CHAR(1));

INSERT INTO t1 VALUES (1, 'a');
INSERT INTO t1 VALUES (2, 'b');
INSERT INTO t1 VALUES (3, 'c');

CREATE FUNCTION do_it()
RETURNS BOOLEAN
VOLATILE
LANGUAGE plpgsql
AS '
DECLARE
_ti INTEGER;
_tc CHAR(1);
_c1 CURSOR FOR SELECT t1i, t1c FROM t1;
BEGIN
OPEN _c1;
FETCH _c1 INTO _ti, _tc;
INSERT INTO t2 VALUES (_ti, _tc);
CLOSE _c1;
RETURN TRUE;
END;
';

SELECT do_it();
DROP FUNCTION do_it();

But watch out, because PL/pgSQL doesn't provide a way to create
SCROLLable cursors, FETCH more than one tuple at a time, or FETCH
orientation.

I urge you to read about functions and PL/pgSQL in the manual:

http://www.postgresql.org/docs/current/static/server-programming.html
http://www.postgresql.org/docs/current/static/plpgsql.html
http://www.postgresql.org/docs/current/static/sql-createfunction.html

and note that SQL DECLARE is a different beast from PL/pgSQL DECLARE,
etc for other statements.

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