vb.org Archive - mysql troubles with left joins

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AN-net

01-14-2006 07:09 PM

mysql troubles with left joins

ok im trying to figure out a way to compare a table to another to find rows that no longer have a parent. similar to orphan thread but my only problem is that the column names are different but hold the same data. so the USE() function isnt possible and i do not think ON() will work because it will only find the rows that do coinside with table 1 from table 2. basically i want find journals that no longer have journalists and remove them.

sabret00the

01-14-2006 10:04 PM

what i'd personally do is run a high tensity script doing all the work in php.

PHP Code:


		
			
$users = U_QUERY;

while ($all_users = $db->fetch_array(U_QUERY))

{

    $current_users[] = $all_users['userid'];

}



$journals = J_QUERY;



while ($all_journals = $db->fetch_array(J_USERS))

{

  if (!in_array($all_journals['userid'], $current_users))

  {

    $journals_to_be_deleted = $all_journals['userid'] . ", ";

  }

}



// do delete query here

something like that :)

AN-net

01-15-2006 01:08 PM

thanks for the suggestion but not what i was looking for ;)

sabret00the

01-15-2006 01:48 PM

Quote:

Originally Posted by AN-net

thanks for the suggestion but not what i was looking for ;)

i know but atleast it's something ;)

Paul M

01-15-2006 02:44 PM

Code:

SELECT * from table1 

LEFT JOIN table2 ON (table1.column1 = table2.column2)

WHERE table2.column2 = NULL

Should find any entries in table1 that don't have a matching entry in table2 (column1 & column2 are the same data you referred to with different names in each table).

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