Updating several records in a database with increasing value - php

Question

I need to update several records in a table, and am hoping to accomplish it in one query.
I have a php array of id's for a few of the records in my table. The array is in a specific order, and I need to update a value for each id with the position/key that the id is in the array. I could easily loop through each value in the array and run a query for each record that needs to be updated, but I am looking for a way to possibly update each record in one query.
The following will give me the desired result, but I am looking for a one query solution.
$ID = array('3','2','6','5','9');
for($i = 0; $i <= 4; $i++){
$q = "UPDATE table SET blah = ".$i." WHERE id = ".$ID[$i];
mysql_query($q) or die();
}
Thanks.

Answer 1

2 queries:
First only needed in case you have used #var already.
SET #var := -1;
And then (note FIND_IN_SET wants a comma-separated string):
UPDATE tablename
SET blah = #var := #var +1
WHERE id IN (3,2,6,5,9)
ORDER BY FIND_IN_SET(id,'3,2,6,5,9');
If you have an array with key=>postition pairs, this could be used:
$array = array(2 => 40,3 => 12,5 => 8,6 => 9,9 =>13129);
mysql_query("
UPDATE bla
SET blah = ELT(
FIELD(id,".implode(',',array_keys($array))."),
".implode(',',$array).")
WHERE id IN (".implode(',',array_keys($array)).")");

Answer 2

A big long ugly if or case statement would do the trick:
UPDATE ...
SET blah = IF(id=3,1,IF(id=2, 2, IF(id=6,3, IF....))))
WHERE id IN (3,2,6,....)
it'd quickly become unmanageable, but it would accomplish things in a single query. A slightly cleaner, more portable alternative:
UPDATE
SET blah = CASE id WHEN 3 THEN 1 WHEN 2 THEN 2 WHEN 6 THEN 3 .... END CASE
WHERE id in (3,2,6,...)

Answer 3

Try this:
INSERT INTO tbl_name (idCol, valCol) VALUES (id1, value1),(id2, value2)
ON DUPLICATE KEY UPDATE
idCol = VALUE(idCol),
valCol = VALUE(valCol)
You could also use a stored procedure, passing it a string of the ID's:
CREATE PROCEDURE updateItems( firstNum INT NOT NULL, ids TEXT NOT NULL) BEGIN
#id := ... # Some expression to get the first ID.
WHILE id != "" DO
SET ids := ... # Some expression to get the rest of the string.
UPDATE table SET blah = firstNum WHERE id = #id;
SET firstNum = firstNum +1;
#id := ... ;
END;
END $$
Also, there was one trick with LAST_INSERT_ID() - if you call it with a param, like LAST_INSERT_ID( 123 ), successive call to LAST_INSERT_ID() will give you 123.
Could be used together with #variables to achieve that goal.
You might get some inspiration here: http://ondra.zizka.cz/stranky/programovani/sql/mysql_stored_procedures.texy

Answer 4

It's impossible in this way ...Well, it's possible but I'd suggest you not to do it, 5 queries aren't horrors

Answer 5

$q = "UPDATE table SET blah = ".$i." WHERE id in ('3','2','6','5','9')";

Answer 6

If you are concerned about performance, you should take a look at using prepared statements and transactions.
There is most likely a solution to doing this in one single query, but it would most likely get really messy.

Answer 7

your better of using foreach then you don't have to set a $i limit.
i think its quick to do it this way
$id = array('3','2','6','5','9');
$i=0;
foreach ($id as $v){
$q = "UPDATE table SET blah = ".$i++." WHERE id = '$v'";
mysql_query($q) or die();
}