I'm implementing a memcache to cache mysql query results.
It loops through the mysql results using
while($rowP3= mysql_fetch_array($result3)) {
or it loops through the memcached results (if they are saved in memcache, and not expired) via
foreach($cch_active_users_final as $rowP3) {
How can I get it to show the right looping method based on if the memcached value exists or not. I just want it to pick the right looping method. I could just duplicate the entire while { } function with all its contents, but I don't want to repeat that huge chunk of code, just so I can change while to foreach
The logic should be something like:
(partial pseudocode)
$data = get_memcached_data('cch_active_users_final');
if (!$data) {
$query = mysql_query(..);
$data = array();
while($row = mysql_fetch_array()) {
$data[] = $row;
}
store_in_memcache('cch_active_users_final', $data);
}
// do whatever you want with $data
If I understand your question, this code doesn't make sense. After querying database comparing queried results to cached values doesn't make sense.
If the $row and $rowP3 values contain the same data, you could have whatever happends in the loops in a function, and pass the row as an argument.
You don't, you use a unified method using PDO.
Related
With php ibase, ibase_query fetches the relation, several functions can then fetch rows from that relation, but all these functions extract the next row.
In Delphi I have the ability to return to the first row (DataSet.First;) - is there any equivalent in PHP ibase?
I could of course re-query the database, but this seems a waste of resources if the original relation is still accessible.
Example code:
$table = ibase_query($sql);
$row = ibase_fetch_object($table);
while (!empty($row))
{
echo $row->ENTRYNO.'<br>';
$row = ibase_fetch_object($table);
}
//The missing functionality
$table.First;
//or maybe
$row = ibase_fetch_object($table,first);
//in which case of course the following line would be redundant
$row = ibase_fetch_object($table);
while (!empty($row))
{
//process record
$row = ibase_fetch_object($table);
}
The ibase/firebird-php driver is only able to fetch forward. If you want to consult earlier rows, you will need to store them yourself in some form, or execute the query again.
So, here's my issue: I have a function that queries sql and pulls it into a resource. In this function, I run:
if (odbc_num_rows($rs) === 0) {
return FALSE;
} else {
if ($type !== "Issues") {
while (odbc_fetch_row($rs)) {
$issues['tvi'][] = odbc_result($rs, 'TitleVolumeIssue_c_');
}
}
return $rs;
}
This does exactly what it is supposed to do. However, when I pass $rs into the next method for parsing into html, it seems as though $rs gets unset. Oddly, I can call odbc_num_rows($rs) and it gives me the correct number of rows, but dumping the var shows it is false and I can't loop through the resource to get any values.
How can I either free up that resource so that it can be used in the next function or how can I rewrite the IF condition so that I get the values without unsetting the resource?
Each time you fetch it moves the database cursor to the next row.
So odbc_fetch_row() keeps going to the next row, until the last one. After that it returns false.
Unfortunately you cannot move the row pointer back to the first record.
You will have to query your DB one more time.
Another option for this would be to store the odbc result in an array that you can loop through using a foreach. This preserves the data and you only have to query once vs multiple times (helps when dealing with a lot of data).
while($row = odbc_fetch_array($rs)) {
$resultsArray[] = $row;
}
Then loop through it like this...
foreach ($resultsArray as $key=>$value){
//Do what you need to do...
}
I had a similar problem in my question here and #Jeff Puckett was able to explain it pretty well.
I'm trying to create a while loop in PHP which retrieves data from a database and puts it into an array. This while loop should only work until the array its filling contains a certain value.
Is there a way to scan through the array and look for the value while the loop is still busy?
to put it bluntly;
$array = array();
$sql = mysql_query("SELECT * FROM table");
while($row = mysql_fetch_array($sql)){
//Do stuff
//add it to the array
while($array !=) //<-- I need to check the array here
}
You can use in_array function and break statement to check if value is in array and then stop looping.
First off, I think it'd be easier to check what you're filling the array with instead of checking the array itself. As the filled array grows, searching it will take longer and longer. Insted, consider:
$array = array_merge($array, $row);
if (in_array('ThisisWhatIneed', $row)
{
break;//leaves the while-loop
}
However, if you're query is returning more data, consider changing it to return what you need, only process the data that needs to be processed, otherwise, you might as well end up with code that does something like:
$stmt = $db->query('SELECT * FROM tbl');
while($row = $stmt->fetch(PDO::FETCH_ASSOC))
{
if ($row['dataField'] === 'username')
{
$user = $row;
break;
}
}
WHERE could help a lot here, don't you think? As well taking advantage of MySQL's specific SELECT syntax, as in SELECT fields, you, need FROM table, which is more efficient.
You may also have noticed that the code above uses PDO, not mysql_*. Why? Simply because the mysql_* extension Is deprecated and should not be used anymore
Read what the red-warning-boxes tell you on every mysql* page. They're not just there to add some colour, and to liven things up. They are genuine wanrings.
Why don't you just check each value when it gets inserted into the array? It is much more efficient than iterating over the whole array each time you want to check.
$array = array();
$stopValue = ...
$sql = mysql_query("SELECT * FROM table");
while($row = mysql_fetch_assoc($sql)){
array_push($array,$row['column']);
if($row['column'] == $stopValue){
// The array now contains the stop value
break;
}
I want to loop multiple times through my query results, and I have 2 ways in mind:
1-
while($data = mysql_fetch_array($res , MYSQL_ASSOC)
{
array_push($new_arr , $data);
}
foreach($sites as $s){
foreach($new_arr as $d)
{
//some code
}
}
2-
foreach($sites as $s){
while($data = mysql_fetch_array($res , MYSQL_ASSOC)
{
//some code
}
mysql_data_seek($res,0);//set the pointer
}
My question: I think option 2 is more efficient but what if I lose connection to db during the mysql_fetch_array(option 2)? I get allot of results; this will take around 10-20 minutes. Will that affect the query results($res) or are they safe?
The data is mapped into a buffer assigned by the mysql client when you execute mysql_query() therefore losing the connection is irrelevant. The first method you cite will create a further copy of the data as a PHP array - which is not very efficient.
Also, WTF is the nested loop ($sites) doing? It looks like either your data is not mormalized or you've got a very bad algorithm.
I have this method in my db class
public function query($queryString)
{
if (!$this->_connected) $this->_connectToDb(); //connect to database
$results = mysql_query($queryString, $this->_dbLink) or trigger_error(mysql_error());
return mysql_num_rows($results) > 0 ? mysql_fetch_assoc($results) : false;
}
This works great for queries that return 1 row, but how can I get an array returned something like this?
$array[0]['name'] = 'jim'
$array[0]['id'] = 120
$array[1]['name'] = 'judith'
$array[1]['ID'] = 121
Now I know I could use a while loop to insert this data into the array like so, but I was wondering if PHP could do this with an internal function? I havn't been able to find on the docs what I'm after.
The reason I don't want to run the while within the method is because I am going to reiterate back over the array when it's returned, and I'd rather not run through the results twice (for performance reasons).
Is there a way to do this? Do I have a problem with my general query method design?
Thank you muchly!
public function query($queryString)
{
if (!$this->_connected) $this->_connectToDb(); //connect to database
$results = mysql_query($queryString, $this->_dbLink) or trigger_error(mysql_error());
$data = array();
while($row = mysql_fetch_assoc($results))
{
$data[] = $row;
}
return $data;
}
this will always return an array.
EDIT:
I didn't read the question well.
If you realy don't want to use the loop then I would do this:
public function query($queryString)
{
if (!$this->_connected) $this->_connectToDb(); //connect to database
return mysql_query($queryString, $this->_dbLink) or trigger_error(mysql_error());
}
then loop over it, however I would just use the loop.
You might also want to look at the PDO extension. You can load the entire result set into an array or you can loop using foreach.
<?php
$db = new PDO($connection_string, $username, $password);
$result = $db->query($queryString);
foreach($result as $row) {
// do something
}
// or
$result = $db->query($queryString);
$result_array = $result->fetchAll(PDO::FETCH_ASSOC);
?>
Most people use a while() loop in the query to do exactly what you want and then loop over the array to process it.
However, you're right: it wastes memory, which could be a problem with a large dataset. An alternative is for your query method to return the resultset resource. Then your while loop can use that to fetch each row as it requires it.
To abstract that away, I would suggest another class to do that for you. Then your query call would return a new instance of that class which has the MySQL resultset resource as an instance variable and packages up the mysql_fetch_assoc() call.
Look at PEAR::MDB2 (Quickstart Cheatsheet). It provides lots of different functions for doing something like this. It also does not tie you down into using MySQL specific functions because it is a database abstraction layer.
$result = $db->queryRow($query, MDB2_FETCHMODE_ASSOC);
There are other abstraction layers such as ADO as well.
thanks for the ideas. I have a function that returns an associative array from the sql (used in Moodle).
$results = get_records_sql($sql);
//to create a numerically indexed array:
$data = array();
foreach ($results as $row)
{
$data[] = $row;
}
return $data;
}