Обсуждение: How to declare cursor if tablename is a variable?

See this:
“CREATE or replace function geo_polygon(tablename varchar) RETURNS integer 
AS $$
DECLARE   objectid varchar;   tab varchar;   x1 float;   y1 float;      obj_num integer;   point_num integer;
   polygonstr varchar;      cur_obj CURSOR FOR SELECT mrc_xy_position FROM tablename;       cur_point CURSOR FOR SELECT
x,yFROM tablename where mrc_xy_position = 
 
objectid;

BEGIN   
…….“

Error if call the function. Neither to use “execute” . Who can solve it? 
Thanks!

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On Wed, Mar 14, 2007 at 08:14:07AM +0000, hu js wrote:
> CREATE or replace function geo_polygon(tablename varchar) RETURNS 
> [...]
>    cur_obj CURSOR FOR SELECT mrc_xy_position FROM tablename;    
>    cur_point CURSOR FOR SELECT x,y FROM tablename where mrc_xy_position = 
> objectid;
> 
> Error if call the function. Neither to use “execute” . Who can solve 
> it? Thanks!

Are you sure you need to use cursors?  Can you not build the query
strings and use EXECUTE or "FOR variable IN EXECUTE query LOOP"?

-- 
Michael Fuhr

[Please copy the mailing list on replies so others can participate
in and learn from the discussion.]

On Tue, Mar 20, 2007 at 02:28:15AM +0000, hu js wrote:
> It doesn't work. Because can't use variable for table name in query.
> 
> Please tell me another way. Thanks

What exactly have you tried that doesn't work?  Will neither of the
following do what you want?  What version of PostgreSQL are you using?

DECLARE rec_obj    record; query_obj  text := 'SELECT mrc_xy_position FROM ' || quote_ident(tablename);
BEGIN FOR rec_obj IN EXECUTE query_obj LOOP   [...] END LOOP;

or

DECLARE cur_obj    refcursor; query_obj  text := 'SELECT mrc_xy_position FROM ' || quote_ident(tablename);
BEGIN OPEN cur_obj FOR EXECUTE query_obj; [...]

-- 
Michael Fuhr

On Wed, Mar 21, 2007 at 02:20:21AM +0000, hu js wrote:
> But I get into another trouble.See following program.

As I requested before, please post questions to the mailing list
so others can participate in and learn from the discussion.

> "query_xypos" is ok. but "query_xydata" is not ok.
> I find "objectid" not quoted corrected.It seems relevant with variable 
> varchar and "'".
[...]
>    query_xypos text := 'SELECT mrc_xy_position FROM ' || 
> quote_ident(tablename);
>    query_xydata text := 'SELECT x,y FROM ' || tablename || ' where 
> mrc_xy_position = ' || quote_ident(objectid) ;

See the documentation to learn more about quote_ident() and
quote_literal() and when to use each:

http://www.postgresql.org/docs/8.2/interactive/plpgsql-statements.html#PLPGSQL-STATEMENTS-EXECUTING-DYN
http://www.postgresql.org/docs/8.2/interactive/functions-string.html#FUNCTIONS-STRING-OTHER

-- 
Michael Fuhr