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How to: IFNULL(SELECT ...,0)

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Old 10-22-2010
How to: IFNULL(SELECT ...,0)
Hi all,

Wondering is this possible:

SELECT id AS cid, name, phone, url, streettype, IFNULL((SELECT ROUND(AVG(stars)*2, 1) / 2 FROM " . $dbconf{'prefix'} . "reviews WHERE location=cid) AS avgstars,0), ...

OR should it be:

SELECT id AS cid, name, phone, url, streettype, (SELECT ROUND(AVG(stars)*2, 1) / 2 FROM " . $dbconf{'prefix'} . "reviews WHERE location=cid) AS IFNULL(avgstars,0), ...

I am fairly sure you can see what I am trying to achieve here.

In other words, two tables, one with id's and another that relates those ID's to star ratings.
I want to extract the AVG(stars) rating AS avgstars to operate on it later, but, if there is no results for the query: ie. no row exists with the "location" specified, can I make the return "avgstars" equal zero rather than simply NULL.

Thanks,
Aaron.
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LEARN ABOUT PHP

db2_num_rows

DB2_NUM_ROWS(3) 							 1							   DB2_NUM_ROWS(3)

db2_num_rows - Returns the number of rows affected by an SQL statement

SYNOPSIS

       int db2_num_rows (resource  $stmt)

DESCRIPTION

	Returns the number of rows deleted, inserted, or updated by an SQL statement.

	To  determine  the  number  of	rows  that  will be returned by a SELECT statement, issue SELECT COUNT(*) with the same predicates as your
       intended SELECT statement and retrieve the value.

	If your application logic checks the number of rows returned by a SELECT statement and branches if the number of rows is 0, consider modi-
       fying  your  application  to  attempt  to  return  the  first row with one of db2_fetch_assoc(3), db2_fetch_both(3), db2_fetch_array(3), or
       db2_fetch_row(3), and branch if the fetch function returns FALSE.

       Note

	       If you issue a SELECT statement using a scrollable cursor, db2_num_rows(3) returns the number of rows returned by the SELECT state-
	      ment.  However,  the  overhead  associated with scrollable cursors significantly degrades the performance of your application, so if
	      this is the only reason you are considering using scrollable cursors, you should use a forward-only cursor and  either  call  SELECT
	      COUNT(*) or rely on the boolean return value of the fetch functions to achieve the equivalent functionality with much better perfor-
	      mance.

PARAMETERS

	      o $stmt
		- A valid stmt resource containing a result set.

RETURN VALUES

	Returns the number of rows affected by the last SQL statement issued by the specified statement handle.

PHP Documentation Group 													   DB2_NUM_ROWS(3)