I'm trying to create a iterate through a row in a MySQL table in one of my CodeIgniter projects, how could I "loop" through the table? Is it just a simple for loop like in other languages?
EDIT:
The answer is as followed:
$query = $this->db->get('mytable'); // select table "mytable" from database
foreach ($query->result() as $row) { // loop thru table and access each row's field
// by using $row->fieldname
}
Maybe something like this
//$this->db->limit(10); // Optional if you want to limit, read about it
$result = $this->db->get('server'); //return all rows
foreach ($result as $row) {
$row->status = 'inactive'; // change value of status attribute or whatever
$this->db->update('server', $row)
}
Or maybe use $this->db->update_batch(); to update a stack of rows at one time.
I encourage you to read the CI database class documentation too.
Another suggestion, is to do all the business logic inside a model instead of a controller. But it's a matter of personal preference maybe.
Related
I'm checking an PHP project which is build using PHP Codeigniter. I'm new to PHP, I like to get your valuable feedback
To retrieve name and item number in php library/controller, call is made to Item Model as below
'name'=>$this->CI->Item->get_info($item_id)->name
'item_number'=>$this->CI->Item->get_info($item_id)->item_number
I suspect above two line of code will make two independent database sql call instead of one call to retrive the two column of same table. Ie., there will be performance degrade. But somebody can please let me know whether it fires two sql statements please?
I think we need to handle like object
$row = $this->CI->Item->get_info($item_id);
echo $row->name;
echo $row->item_number;
Please suggest. Thanks in advance.
Model Function:
function get_info($item_id)
{
$this->db->from('items');
$this->db->where('item_id',$item_id);
$query = $this->db->get();
if($query->num_rows()==1)
{
return $query->row();
}
else
{
//Get empty base parent object, as $item_id is NOT an item
$item_obj=new stdClass();
//Get all the fields from items table
$fields = $this->db->list_fields('items');
foreach ($fields as $field)
{
$item_obj->$field='';
}
return $item_obj;
}
}
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Is it possible to query a tree structure table in MySQL in a single query, to any depth?
I have an admin area I created that pulls data from the mysql database using php and display the results in a table. Basically it shows a parent category, then the first sub category below it, then the third level sub category/subject.
It works perfectly but as I am new to mysql and php I am sure that it the code needs to be improved in order to save db resources as while building the table I use 3 while loops and in each loop make a mysql query which I am sure is the wrong way to do it.
Can somebody offer me some assistance for the best way of doing this?
Here is the code:
$query = mysql_query("SELECT * FROM categories WHERE
parent_id is null
order by cat_id asc;", $hd)
or die ("Unable to run query");
while ($row = mysql_fetch_assoc($query)) {
echo '<tr style="font-weight:bold;color:green;"><td>'. $row ['cat_id'].'</td><td>'.$row['cat_name'].'</td><td>'.$row ['parent_id'].'</td><td>'.$row['active'].'</td><td>'.$row ['url'].'</td><td>'.$row['date_updated'].'</td></tr>' ;
$query2 = mysql_query("SELECT * FROM categories WHERE
(active = 'true' AND parent_id = ".$row ['cat_id'].")
order by cat_id asc;", $hd)
or die ("Unable to run query");
while ($row2 = mysql_fetch_assoc($query2)) {
echo '<tr style="font-weight:bold;"><td>'. $row2['cat_id'].'</td><td>'.$row2 ['cat_name'].'</td><td>'.$row2['parent_id'].'</td><td>'.$row2 ['active'].'</td><td>'.$row2['url'].'</td><td>'.$row2 ['date_updated'].'</td></tr>' ;
$query3 = mysql_query("SELECT * FROM categories WHERE
(active = 'true' AND parent_id = ".$row2 ['cat_id'].")
order by cat_id asc;", $hd)
or die ("Unable to run query");
while ($row3 = mysql_fetch_assoc($query3)) {
echo '<tr><td>'. $row3['cat_id'].'</td><td>'.$row3['cat_name'].'</td><td>'.$row3 ['parent_id'].'</td><td>'.$row3['active'].'</td><td>'.$row3 ['url'].'</td><td>'.$row3['date_updated'].'</td></tr>' ;
}
}
}
EDIT
Ok so I did a bit of research and this is where I am:
Probably for a small database my approach is fine.
For a bigger database using an array to store the data would probably mean I need to use a recursive approach which might use up too much memory. Would love to hear what people think, would it still be better than looping db queries in the nested while loops?
I found the following thread where there is an answer to do this without reccursion and with only one query. Not sure if I need to add a position column to my current design:
How to build unlimited level of menu through PHP and mysql
If I rebuild the design using the nested sets model instead of adjacency model then the mysql query would return the results in the required order however maintaining the nested sets design is above my head and I think would be overkill.
That's it. If anyone has any input on top of that please add to the conversation. There must be a winning approach as this kind of requirement must be needed for loads of web applications.
I would think you could do something like this:
SELECT * FROM categories
WHERE active = 'true'
ORDER BY parent_id, cat_id
This would give you all your categories ordered by parent_id, then by cat_id. You would then take the result set and build a multi-dimensional array from it. You could then loop through this array much as you currently do in order to output the categories.
While this is better from a DB access standpoint, it would also consume more memory as you need to keep this larger array in memory. So it really is a trade-off that you need to consider.
There is a lot to fix there, but I'll just address your question about reducing queries. I suggest getting rid of the WHERE clauses all together and use if statements within the while loop. Use external variables to hold all the results that match a particular condition, then echo them all at once after the loop. Something like this (I put a bunch of your stuff in variables for brevity)
//before loop
$firstInfoSet = '';
$secondInfoSet = '';
$thirdInfoSet = '';
//in while loop
if($parentID == NULL)
{
$firstInfoSet.= $yourFirstLineOfHtml;
}
if($active && $parentID == $catID) // good for query 2 and 3 as they are identical
{
$secondInfoSet.= $yourSecondLineOfHtml;
$thirdInfoSet.= $yourThirdLineOfHtml;
}
//after loop
echo $firstInfoSet . $secondInfoSet . $thirdInfoSet;
You can now make whatever kinds of groupings you want, easily modify them if need be, and put the results wherever you want.
--EDIT--
After better understanding the question...
$query = mysql_query("SELECT * FROM categories order by cat_id asc;", $hd);
$while ($row = mysql_fetch_assoc($query)){
if($row['parent_id'] == NULL){
//echo out your desired html from your first query
}
if($row['active'] && $row['parent_id']== $row['cat_id']){
//echo out your desired html from your 2nd and 3rd queries
}
}
I'm implementing a memcache to cache mysql query results.
It loops through the mysql results using
while($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.
I have a table but I dont know what the columns are except for 1 column. There is only 1 permanent data value for each row, the rest of the columns are added and removed elsewhere. This isnt a problem for the query, i just do:
SELECT * FROM table
but for the php function bind_result() i need to give it variables for each column, which i do not know.
I think that once I have the columns in an array, I can do anther query and use call_user_func_array to bind the result to the array.
This seems like it would come up a lot so im wondering is there a standard way of doing this?
Couldn't you just do:
$result = mysql_query("SELECT * FROM table");
while ($row = mysql_fetch_assoc($result))
{
foreach ($row as $field => $value)
{
...
}
}
You could do
show columns from table;
And then parse that string to grab your column names.
You can also try the describe command, which is used to list all of the fields in a table and the data format of each field. Usage:
describe TableName;
you can use
$metadata = $prep_statement->result_metadata()
after you executed the statement and then loop through all result fields using something like
while( $field = $metadata->fetch_field() ) { }
the properties of $field are documented here: http://www.php.net/manual/en/mysqli-result.fetch-field.php
I have two dynamic tables (tabx and taby) which are created and maintained through a php interface where columns can be added, deleted, renamed etc.
I want to read all columns simulataneously from the two tables like so;-
select * from tabx,taby where ... ;
I want to be able to tell from the result of the query whether each column came from either tabx or taby - is there a way to force mysql to return fully qualified column names e.g. tabx.col1, tabx.col2, taby.coln etc?
In PHP, you can get the field information from the result, like so (stolen from a project I wrote long ago):
/*
Similar to mysql_fetch_assoc(), this function returns an associative array
given a mysql resource, but prepends the table name (or table alias, if
used in the query) to the column name, effectively namespacing the column
names and allowing SELECTS for column names that would otherwise have collided
when building a row's associative array.
*/
function mysql_fetch_assoc_with_table_names($resource) {
// get a numerically indexed row, which includes all fields, even if their names collide
$row = mysql_fetch_row($resource);
if( ! $row)
return $row;
$result = array();
$size = count($row);
for($i = 0; $i < $size; $i++) {
// now fetch the field information
$info = mysql_fetch_field($resource, $i);
$table = $info->table;
$name = $info->name;
// and make an associative array, where the key is $table.$name
$result["$table.$name"] = $row[$i]; // e.g. $result["user.name"] = "Joe Schmoe";
}
return $result;
}
Then you can use it like this:
$resource = mysql_query("SELECT * FROM user JOIN question USING (user_id)");
while($row = mysql_fetch_assoc_with_table_names($resource)) {
echo $row['question.title'] . ' Asked by ' . $row['user.name'] . "\n";
}
So to answer your question directly, the table name data is always sent by MySQL -- It's up to the client to tell you where each column came from. If you really want MySQL to return each column name unambiguously, you will need to modify your queries to do the aliasing explicitly, like #Shabbyrobe suggested.
select * from tabx tx, taby ty where ... ;
Does:
SELECT tabx.*, taby.* FROM tabx, taby WHERE ...
work?
I'm left wondering what you are trying to accomplish. First of all, adding and removing columns from a table is a strange practice; it implies that the schema of your data is changing at run-time.
Furthermore, to query from the two tables at the same time, there should be some kind of relationship between them. Rows in one table should be correlated in some way with rows of the other table. If this is not the case, you're better off doing two separate SELECT queries.
The answer to your question has already been given: SELECT tablename.* to retrieve all the columns from the given table. This may or may not work correctly if there are columns with the same name in both tables; you should look that up in the documentation.
Could you give us more information on the problem you're trying to solve? I think there's a good chance you're going about this the wrong way.
Leaving aside any questions about why you might want to do this, and why you would want to do a cross join here at all, here's the best way I can come up with off the top of my head.
You could try doing an EXPLAIN on each table and build the select statement programatically from the result. Here's a poor example of a script which will give you a dynamically generated field list with aliases. This will increase the number of queries you perform though as each table in the dynamically generated query will cause an EXPLAIN query to be fired (although this could be mitigated with caching fairly easily).
<?php
$pdo = new PDO($dsn, $user, $pass, array(PDO::ATTR_ERRMODE=>PDO::ERRMODE_EXCEPTION));
function aliasFields($pdo, $table, $delim='__') {
$fields = array();
// gotta sanitise the table name - can't do it with prepared statement
$table = preg_replace('/[^A-z0-9_]/', "", $table);
foreach ($pdo->query("EXPLAIN `".$table."`") as $row) {
$fields[] = $table.'.'.$row['Field'].' as '.$table.$delim.$row['Field'];
}
return $fields;
}
$fieldAliases = array_merge(aliasFields($pdo, 'artist'), aliasFields($pdo, 'event'));
$query = 'SELECT '.implode(', ', $fieldAliases).' FROM artist, event';
echo $query;
The result is a query that looks like this, with the table and column name separated by two underscores (or whatever delimeter you like, see the third parameter to aliasFields()):
// ABOVE PROGRAM'S OUTPUT (assuming database exists)
SELECT artist__artist_id, artist__event_id, artist__artist_name, event__event_id, event__event_name FROM artist, event
From there, when you iterate over the results, you can just do an explode on each field name with the same delimeter to get the table name and field name.
John Douthat's answer is much better than the above. It would only be useful if the field metadata was not returned by the database, as PDO threatens may be the case with some drivers.
Here is a simple snippet for how to do what John suggetsted using PDO instead of mysql_*():
<?php
$pdo = new PDO($dsn, $user, $pass, array(PDO::ATTR_ERRMODE=>PDO::ERRMODE_EXCEPTION));
$query = 'SELECT artist.*, eventartist.* FROM artist, eventartist LIMIT 1';
$stmt = $pdo->prepare($query);
$stmt->execute();
while ($row = $stmt->fetch()) {
foreach ($row as $key=>$value) {
if (is_int($key)) {
$meta = $stmt->getColumnMeta($key);
echo $meta['table'].".".$meta['name']."<br />";
}
}
}