Is this Possible - PHP/MySQL

[Phillip T. Murphy]

Well, after half pulling my hair out messing with this, I am thinking it is
not possible. I did research and found references to "sub-queries" not
possible in MySQL (I am using 4.0.18-32 with PHP 4). But, not sure if I am
breaking that rule or not.

Psuedo code of what I am trying to do...

<?php

$sql = "select * from table1";
$db_result = mysql_query($sql);

while ($row = mysql_fetch_array($db_result)) {
$table_key = $row("table_key");
$sql2 = "select * from table2 where tabel_key='$table_key'";
$db_result2 = mysql_query($sql2);
$row2 = mysql_fetch_array($db_result2);

if record exists in table2
do something with table 2;
else
do something with table 1;
}
?>

The second query seems to always return an empty array. Is this nested
query allowed in PHP/MySQL?

Thanks in advance for any help,

PTM

[Geoff Berrow]

I noticed that Message-ID: <bg**************@bignews5.bellsouth.net>
from Phillip T. Murphy contained the following:

The second query seems to always return an empty array.

tabel_key?
--
Geoff Berrow (put thecat out to email)
It's only Usenet, no one dies.
My opinions, not the committee's, mine.
Simple RFDs http://www.ckdog.co.uk/rfdmaker/

[Michael Fesser]

.oO(Phillip T. Murphy)

Well, after half pulling my hair out messing with this, I am thinking it is
not possible. I did research and found references to "sub-queries" not
possible in MySQL (I am using 4.0.18-32 with PHP 4). But, not sure if I am
breaking that rule or not.
A subquery (or subselect) is a SELECT statement nested inside another:

SELECT something FROM somewhere WHERE foo = (SELECT somethingelse ...)

Subqueries are supported as of MySQL 4.1.
The second query seems to always return an empty array. Is this nested
query allowed in PHP/MySQL?

No problem with that.

But you have no error checking in your code, you won't notice when a
query fails. Check if mysql_query() returns a resource ID, if not have a
look at mysql_error() to see if MySQL encountered a problem.

http://www.php.net/mysql_query
http://www.php.net/mysql_error

Micha

[Phillip T. Murphy]

"Michael Fesser" <ne*****@gmx.net> wrote in message
news:cp********************************@4ax.com...

.oO(Phillip T. Murphy)

Well, after half pulling my hair out messing with this, I am thinking it
is
not possible. I did research and found references to "sub-queries" not
possible in MySQL (I am using 4.0.18-32 with PHP 4). But, not sure if I
am
breaking that rule or not.

A subquery (or subselect) is a SELECT statement nested inside another:

SELECT something FROM somewhere WHERE foo = (SELECT somethingelse ...)

Subqueries are supported as of MySQL 4.1.

The second query seems to always return an empty array. Is this nested
query allowed in PHP/MySQL?

No problem with that.

But you have no error checking in your code, you won't notice when a
query fails. Check if mysql_query() returns a resource ID, if not have a
look at mysql_error() to see if MySQL encountered a problem.

http://www.php.net/mysql_query
http://www.php.net/mysql_error

Micha

Thanks for the quick reply. in the interest of space, I cut that out. I
have a function defined that replaces the mysql_query() call and does error
checking.

At least I know what I am trying to do is possible now. I am starting over.
I would like to be able to just use a LEFT JOIN, but the second table needs
a where clause on a field that does not exist in the first table, so too
many records are elimiated.

I will keep trying. Thanks for the input.

[kingofkolt]

"Phillip T. Murphy" <pS**********@bellsouth.net> wrote in message
news:bg**************@bignews5.bellsouth.net...

Well, after half pulling my hair out messing with this, I am thinking it is not possible. I did research and found references to "sub-queries" not
possible in MySQL (I am using 4.0.18-32 with PHP 4). But, not sure if I am breaking that rule or not.

Psuedo code of what I am trying to do...

<?php

$sql = "select * from table1";
$db_result = mysql_query($sql);

while ($row = mysql_fetch_array($db_result)) {
$table_key = $row("table_key");

[...]

Not sure if/what this will fix, but in that last line ($table_key =
$row("table_key");), the parantheses in $row("table_key") should be changed
to brackets: $row["table_key"]

- JP

[Phillip T. Murphy]

"kingofkolt" <je**********@comcast.net> wrote in message
news:B4ckd.21457$5K2.20313@attbi_s03...

"Phillip T. Murphy" <pS**********@bellsouth.net> wrote in message
news:bg**************@bignews5.bellsouth.net...

Well, after half pulling my hair out messing with this, I am thinking it

is

not possible. I did research and found references to "sub-queries" not
possible in MySQL (I am using 4.0.18-32 with PHP 4). But, not sure if I

am

breaking that rule or not.

Psuedo code of what I am trying to do...

<?php

$sql = "select * from table1";
$db_result = mysql_query($sql);

while ($row = mysql_fetch_array($db_result)) {
$table_key = $row("table_key");

[...]

Not sure if/what this will fix, but in that last line ($table_key =
$row("table_key");), the parantheses in $row("table_key") should be
changed
to brackets: $row["table_key"]

- JP

Thanks for the responses everyone. Thanks to suggestions here and assuring
me that it is possible to do nested queries, I got it to work.

Come to find out, it had to do with the way I was checking if the second
query returned anything or not. When it didn't return anything, I was
checking one of the array variables to see if it was NULL or Blank. That
did not work. I backed up and now check what the mysql_query returns (FALSE
or an Array).

All is now well. As always, coming to a group like this to get answers fast
solved my problem.