sql php find field value from updated row - php

Question

Say I have this loop:
foreach ($array as $a) {
if ($a == $b) {
mysql_query("UPDATE table SET this = 'that' WHERE id='$a'");
}
}
And a table...
id this blah
------------------------
1 that 54
2 that 73
3 there 27
Inside that loop, I also want to find the value stored in the tables blah field from the current record that is being updated.
Whats the most effective way to do this?

Answer 1

You can have your query consist of multiple statements, and the last statement is what is used for the "results".
So, you can just add a "select" statement to the end of the update query and treat it like a normal select statement:
UPDATE table SET this = 'that' WHERE id='$a'; SELECT blah from [your table] WHERE id = '$a'
The advantage with this method is that it doesn't require an additional DB call.
Of course, you will want to be escaping the values put into the SQL statements to prevent SQL injection, but that's another matter.

Answer 2

Update
This was my first second SO answer which I felt needed revising. Searching around, I found a much better answer to your question.
From the accepted answer for question: SQL: Update a row and returning a column value with 1 query
You want the OUTPUT clause
UPDATE Items SET Clicks = Clicks + 1
OUTPUT INSERTED.Name
WHERE Id = #Id
Similar question: Is there a way to SELECT and UPDATE rows at the same time?
Old Answer
Add a SELECT statement to the end of your UPDATE query.
mysql_query("UPDATE table SET this = 'that' WHERE id='$a'; SELECT blah WHERE id='$a';");
This prevents you from ensuring the update took place since mysql_query only returns the last statement's result.
You could also write a custom function that performs both statements but, for instance, won't preform the SELECT if the UPDATE failed, etc.
** Skeleton Function - Not Tested **
function MyUpdate($query, $id){
$retVal = "-1" // some default value
$uResult = mysql_query("UPDATE table SET this = 'that' WHERE id='$a'");
if( $uResult )
$result= mysql_query('SELECT blah WHERE id=$a');
if (!$result) {
die('Invalid query: ' . mysql_error());
}
$retVal = $result;
}
return $retVal;
}