[SQL] PL/PGSQL - How to pass in variables?

[Scott Yohonn]

Using PL/PGSQL, I am trying to create a procedure to display the count of rows in any single table of a database. The End-user would pass in a table name and the prodecure would display the table name with the row count.

I am able to hardcode the variable for table and get the appropriate results from my count function (see below), but cannot pass in a variable and have the function work. Any suggesstions??? CREATE FUNCTION get_table_count(tablename text) RETURNS integer AS $$
DECLARE  --tablename ALIAS FOR $1;   rowcount INTEGER;   BEGIN 
 SELECT INTO rowcount count(*) FROM tablename;  RETURN rowcount;    END; $$ LANGUAGE 'plpgsql'; 

Re: [SQL] PL/PGSQL - How to pass in variables?

[Jean-Paul Argudo]

Hi Scott,

You'll have to execute dynamic SQL (see doc chapter "36.6.5. Executing
Dynamic Commands") for your function to work:

CREATE FUNCTION get_table_count(tablename text) RETURNS integer AS
$$
DECLARE
--tablename ALIAS FOR $1;
 rowcount INTEGER;
  BEGIN

execute 'SELECT count(*) FROM '||tablename into rowcount;
return rowcount;

  END;
$$ LANGUAGE 'plpgsql';


select get_table_count('bar');

 get_table_count
-
   3
(1 row)




Cheers,

-- 
Jean-Paul Argudo
www.PostgreSQLFr.org
www.dalibo.com

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Re: [SQL] PL/PGSQL - How to pass in variables?

[Jaime Casanova]

On 5/14/06, Scott Yohonn <[EMAIL PROTECTED]> wrote:


Using PL/PGSQL, I am trying to create a procedure to display the
count of rows in any single table of a database. The End-user would
pass in a table name and the prodecure would display the table name
with the row count.
I am able to hardcode the variable for table and get the appropriate
results from my count function (see below), but cannot pass in a
variable and have the function work. Any suggesstions???

CREATE FUNCTION get_table_count(tablename text) RETURNS integer AS $$
DECLARE

 --tablename ALIAS FOR $1;

  rowcount INTEGER;
   BEGIN

 SELECT INTO rowcount count(*) FROM tablename;

 RETURN rowcount;

   END;
 $$ LANGUAGE 'plpgsql';



you can't do this because tablename is a variable not a table, you
have to append the content of the variable in a string that can be
EXECUTE'd

EXECUTE 'SELECT count(*) FROM ' || tablename INTO rowcount;

--
regards,
Jaime Casanova

"Programming today is a race between software engineers striving to
build bigger and better idiot-proof programs and the universe trying
to produce bigger and better idiots.
So far, the universe is winning."
  Richard Cook

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Re: [SQL] PL/PGSQL - How to pass in variables?

[Jean-Paul Argudo]

Scott Yohonn wrote:
> Jean-Paul,
> 
> Thanks! This did work. The output put the name of the function
> (get_table_count) as the header. How would I display the name of the table
> that I am requesting the row count of?

The only way I know is to alias the output in the query calling the
function, so:


select get_table_count('bar') as bar;

 bar
-
   3
(1 row)

I don't know any other way to do that...

Cheers,

-- 
Jean-Paul Argudo
www.PostgreSQLFr.org
www.dalibo.com

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