I have asked a question similar to this, but none answered. Im guessing because it was too long that i wasnt able to fully state or make it clear to the general public. Anyways, Is there anyway into reducing an array like this
Array( [0]=>Array( [id]=>name ) [1]=>Array( [id]=>name ) )
The above values came from.
$query=$this->db
->select('id,name')
->from('employees')
->get()
->result_array();
The query above results,
Array([0]=>Array([id]=>1 [name]=>john))
Since i wanted to get all the rows without overwriting the previous rows resulted. I added this algo.
foreach($query as $row)
{
$employee_list[] = array($row['id']=>$row['name']);
}
Now the results are not overwritten so if i print_r($employee_list);
I would echo out, assume there are 2 rows in my employees table.
1-john,2-peter
Array([1]=>Array([1]=>john) [2]=>Array([2]=>peter))
My question now is, how do i reduce the above resulted array to one dimensional/linear. Since the ID is stored as KEY and the id column is INTEGER AUTO INCREMENT PRIMARY KEY so it doesnt have any duplicates which means for every row inserted the id will be incremented.
so it would be fine if the array i wanted would be.
Array([1]=>john [2]=>peter)
Additional INFO: I am using codeigniter as my framework, so if there's any defined function in the CI library, it would help if anyone could tell me if there is any.
In old times you could use mysql_result which selects one column into single dimensional array.
However, it is deprecated since PHP 5.5.0 and the reference suggests using mysqli_fetch_field (which forces you to make a select from the response as zerkms suggest in the comment) or PDOStatement::fetchColumn if you are willing to use PDO.
Related
I am trying to do the following.
I am consulting an external database using a web service. What the web service does is bring me all the products from an ERP system my client uses. As the server and the connection are not really fast, what I decided to do is basically synchronize the database on my web server and handle most operations there, so that the website can run smoothly.
Everything works fine I just need one last step to guarantee that the inventory on the website matches the one available on the ERP. The only issue comes when they (the client) deletes something on the ERP system.
At the moment I am thinking what would be the ideal strategy (least resource and time consuming) to remove products from my Products table if I don't receive them in the web service result.
So I basically have the following process:
I query the web service for all the products, give them a little format and store them in an array. The final size is about 600 indexes.
Then what I do is I do a foreach cycle and have the following subprocess.
I query my database to check if product_id is present.
If the product is present, I just update it with the latest info, stock data.
If the product is not present, I just insert it.
So, I was thinking of doing the following, but I do not think it's the ideal way:
Do a SELECT * FROM Products and generate an array that has all the products.
Do a foreach cycle in the resulting array and in each cycle scan the ERP array to check if the specific product exists. If not I delete it, if yes, I continue with the next product.
Now considering that after all the previous steps this would involve a couple of nested foreach I am a little worried that it might consume too much memory and also take longer to process.
I was thinking that maybe something like array_diff or array map could solve the issue, but I am not really experienced with these functions, and the structure of the two arrays differs a lot, so I am not sure if it would work that easily.
What would you guys recommend?
It's actually quite simple:
SELECT id FROM Products
Then you have an array of your product Ids, for example:
[123,5679,345]
Then as you go and do your updates or inserts, remove the id from the array.
[for updates]I query my database to check if product_id is present.
This is redundant now.
There are a few ways to remove the value from the array (when you do an update), this is the way I would probably do it.
if(false !== ($index = array_search($data['product_id'],$myids))){
//note the !== type comparison because array_search can return 0 for the first index, we must check for boolean false.
//find the index of the product id in our list of id's from local DB
unset($myids[$index]);
//If our incoming product_id is in the local list we Do Update
}else{
//Otherwise we Do Insert
}
As I mentioned above when doing your updates/inserts, You no longer have to check if the ID exists, because you already know this by having an array of IDs from the database. This alone saves you (n) queries (apx 600).
Then its very simple if you have ids left over.
//I wouldn't normally concatenate variables into SQL, in this case it's a list of int IDs from the database.
//you can of course come up with a loop to make it a prepared statement if you wish, but for the sake of simplistically, I'll leave that as an exercise for another day..
'DELETE FROM Products WHERE id IN('.implode(',', $myids).')'
And because you unset these when Updating, then the only thing left is Products that no longer exist.
Conclusion:
You have no choice (other then doing on duplicate key query, or ignoring exceptions) then to pull out the product Ids. You're already doing this on a row by row basis. So we can effectively kill 2 birds with one stone.
If you need more data then just the ID, for example you check that the product was changed before doing an update. Then pull that data out, but I would recommend using PDO and the FETCH_GROUP option. I wont go into the specifics of that but to say it lets you easily build your array this way:
[{product_id} => [ {product_name}, {product_price} etc..]];
Basically the product_id, is the key with a nested array of the row data, this will make lookup easier.
This way you can look it up like this.
//then instead of array_search
//if(false !== ($index = array_search($data['product_id'],$myids))){
if(isset($myids[$data['product_id']])){
unset($myids[$data['product_id']]);
//do your checks, then your update
}else{
//do inserts
}
References:
http://php.net/manual/en/function.array-search.php
array_search — Searches the array for a given value and returns the first corresponding key if successful
WARNING This function may return Boolean FALSE, but may also return a non-Boolean value which evaluates to FALSE. Please read the section on Booleans for more information. Use the === operator for testing the return value of this function.
UPDATE
There is one other really good way to do this, and that is to add a field called sync_date, now when you do your insert or update then set the sync_date to the current data.
This way when you are done, those products with an older sync date then today can be deleted. In this case it's best to cache the time when doing it so you know the exact time.
$time = data('Y-m-d H:i:s'); //or time() if you prefer timestamp
//use this same variable for the whole coarse of the script.
Then you can do
'DELETE from products WHERE sync_time != $time'
This may actually be a bit better because it has more utility. When was the last time it was ran, Now you know.
I'm currently working on a Symfony project, using Doctrine to manage entities.
I have a table named User, containing a few columns, and then another table named Tag, containing a foreign key to that User table with a ManyToOne relation based on the user id, and a single other column named value.
In my app, I need to find a list of users, depending on one of the Tag row, AND the value of one of the User's column. Let's resume :
Select all users where user.value equals somevalue AND Tag.value equals anothervalue.
As I never used Symfony nor Doctrine before this project, I searched into Doctrine documentation and found about the Query Builder. So, I did this :
EDIT : The way I was doing it was kinda weird, so I modified it and here is the result :
public function findByTagAndApp($tag, $app)
{
$em = $this->getEntityManager();
$qb = $em
->getRepository('APIBundle:User')
->createQueryBuilder('u')
->leftJoin('APIBundle\Entity\Tag', 't')
->where('u.application = :app')
->andWhere('t.tag = :tag')
->setParameter('tag', $tag)
->setParameter('app', $app)
;
$users = $qb->getQuery()->getResult();
return $users;
}
And it seems like it works, but in a strange way. Instead of returning an array of User items, which is what I want, it returns an array of array of User items. The first array is always containing two entries, and these two entries are always identical : they are the array I need, without a single difference.
I tried to do return $users[0] instead of just users, and then I can manipulate my User entities the intended way. I could keep it this way as it is working, but I'd really like to know why it returns an unneeded array of array instead of just the array I want. It might be my query, but I'm not sure how to modify it to get only the Users I want.
Any clues on why it behave like this would be really appreciated, as I'm still learning about Doctrine. Thanks !
EDIT² : Nevermind, this query seems completely incorrect too, as I got all users according to the $app value, but it seems like it never check if there is a row in the Tag table with a value of somevalue associated to a foreign key of the User table..
I don't know exactly why it is but..
I think you have to mention from() like ->from('User', 'u')
for extra you can find here
After a few hours of tweaking, I figured it out using SQL statement on PhpMyAdmin, so I could notice that there was a LOT of things that I was doing wrong :
First, the join was not correct. My goal was to collect users that had a certain value in their own table, AND a value from the Tag table. Using a left join, I was collecting users with their own value OR a the value from the Tag table.
Second : The $app value I was passing was an object of type Application (the Application field in my User table is a foreign key), and the query builder didn't know what to do with it. Passing the app_id instead of the app object solved the problem.
Third : The way I collected result was wrong. Obviously, this query returns an array of User objects. And as I execute this query multiple times in a row, I had an array on which I used array_push to fill it with the data, thinking that pushing array1 with array2 would put array2 values into array1, but it was just putting array2 into array1, resulting to that array of arrays that was the initial problem. Using array_merge instead of array_push, I am now able to collect all the results from the queries into a single array. A little array_unique on that to avoid redundancy, and everything is working as expected.
Thanks to everyone who replied !
I'm using PHP but that's not important. I have a variable that contains a standard array of positive int IDs. And I want to do a SELECT query with this array against a MySQL table to find out what IDs are not already existing in the data table. My first thought was to use IN() but then I realized that doing it that way I can only get a list of IDs that do exist not ones that don't. Of course with a list of IDs that do exist, I could compile it into a second array and then use array_diff() but I can't help wondering if there's another way to do it.
I decided to use unset()
SELECT QUERY
where (row) {
unset(id)
}
I'm not sure that I have the terminology correct but basically I have a website where members can subscribe to topics that they like and their details go into a 'favorites' table. Then when there is an update made to that topic I want each member to be sent a notification.
What I have so far is:
$update_topic_sql = "UPDATE topics SET ...My Code Here...";
$update_topic_res = mysqli_query($con, $update_topic_sql)or die(mysqli_error());
$get_favs_sql = "SELECT member FROM favourites WHERE topic = '$topic'";
$get_favs_res = mysqli_query($con, $get_favs_sql);
//Here I Need to update the Members selected above and enter them into a notes table
$insert_note_sql = "INSERT INTO notes ....";
Does anyone know how this can be achieved?
Ok, so we've got our result set of users. Now, I'm going to assume from the nature of the question that you may be a bit of a newcomer to either PHP, SQL(MySQL in this case), web development, or all of the above.
Your question part 1:
I have no idea how to create an array
This is easier than what you may think, and if you've already tried this then I apologize, I don't want to insult your intelligence. :)
Getting an array from a mysqli query is just a matter of a function call and a loop. When you ran your select query and saved the return value to a variable, you stored a mysqli result set. The mysqli library supports both procedural and object oriented styles, so since you're using the procedural method, so will I.
You've got your result set
$get_favs_res = mysqli_query($con, $get_favs_sql);
Now we need an array! At this point we need to think about exactly what our array should be of, and what we need to do with the contents of the request. You've stated that you want to make an array out of the results of the SELECT query
For the purposes of example, I'm going to assume that the "member" field you've returned is an ID of some sort, and therefore a numeric type, probably of type integer. I also don't know what your tables look like, so I'll be making some assumptions there too.
Method 1
//perform the operations needed on a per row basis
while($row = mysqli_fetch_assoc($get_favs_res)){
echo $row['member'];
}
Method 2
//instead of having to do all operations inside the loop, just make one big array out of the result set
$memberArr = array();
while($row = mysqli_fetch_assoc($get_favs_res)){
$memberArr[] = $row;
}
So what did we do there? Let's start from the beginning to give you an idea of how the array is actually being generated. First, the conditional in the while loop. We're setting a variable as the loop condition? Yup! And why is that? Because when PHP (and a lot of other languages) sets that variable, the conditional will check against the value of the variable for true or false.
Ok, so how does it get set to false? Remember, any non boolean false, non null, non 0 (assuming no type checking) resolves to true when it's assigned to something (again, no type checking).
The function returns one row at a time in the format of an associative array (hence the _assoc suffix). The keys to that associative array are simply the names of the columns from the row. So, in your case, there will be one value in the row array with the name "member". Each time mysqli_fetch_assoc() is called with your result set, a pointer is pointed to the next result in the set (it's an ordered set) and the process repeats itself. You essentially get a new array each time the loop iterates, and the pointer goes to the next result too. Eventually, the pointer will hit the end of the result set, in which case the function will return a NULL. Once the conditional picks up on that NULL, it'll exit.
In the second example, we're doing the exact same thing as the first. Grabbing an associative array for each row, but we're doing something a little differently. We're constructing a two dimensional array, or nested array, of rows. In this way, we can create a numerically indexed array of associative arrays. What have we done? Stored all the rows in one big array! So doing things like
$memberArr[0]['member'];//will return the id of the first member returned
$memberArr[1]['member'];//will return the id of the second member returned
$lastIndex = sizeof($memberArr-1);
$memberArr[$lastIndex]['member'];//will return the id of the last member returned.
Nifty!!!
That's all it takes to make your array. If you choose either method and do a print_r($row) (method 1) or print_r($memberArr) (method 2) you'll see what I'm talking about.
You question part 2:
Here I Need to update the Members selected above and enter them into a notes table
This is where things can get kind of murky and crazy. If you followed method 1 above, you'd pretty much have to call
mysqli_query("INSERT INTO notes VALUES($row['member']);
for each iteration of the loop. That'll work, but if you've got 10000 members, that's 10000 inserts into your table, kinda crap if you ask me!
If you follow method two above, you have an advantage. You have a useful data structure (that two dim array) that you can then further process to get better performance and make fewer queries. However, even from that point you've got some challenges, even with our new processing friendly array.
The first thing you can do, and this is fine for a small set of users, is use a multi-insert. This just involves some simple string building (which in and of itself can pose some issues, so don't rely on this all the time) We're gonna build a SQL query string to insert everything using our results. A multi insert query in MySQL is just like a normal INSERT except for one different: INSERT INTO notes VALUES (1),(2),(x)
Basically, for each row you are inserted, you separate the value set, that set delineated by (), with a comma.
$query = 'INSERT INTO notes VALUES ';
//now we need to iterate over our array. You have your choice of loops, but since it's numerically indexed, just go with a simple for loop
$numMembers = sizeof($memberArr);
for($i = 0; $i < $numMembers; $i++){
if($i > 0){
$query .= ",({$membersArr[$i]['member']})";//all but the first row need a comma
}
else {
$query .= "({$membersArr[$i]['member']})";//first row does not need a comma
}
}
mysqli_query($query);//add all the rows.
Doesn't matter how many rows you need to add, this will add them. However, this is still going to be a costly way to do things, and if you think your sets are going to be huge, don't use it. You're going to end up with a huge string, TONS of string concats, and an enormous query to run.
However, given the above, you can do what you're trying to do.
NOTE: These are grossly simplified ways of doing things, but I do it this way because I want you to get the fundamentals down before trying something that's going to be way more advanced. Someone is probably going to comment on this answer without reading this note telling me I don't know what I'm doing for going about this so dumbly. Remember, these are just the basics, and in no way reflect industrial strength techniques.
If you're curious about other ways of generating arrays from a mysqli result set:
The one I used above
An even easier way to make your big array but I wanted to show you the basic way of doing things before giving you the shortcuts. This is also one of those functions you shouldn't use much anyway.
Single row as associative(as bove), numeric, or both.
Some folks recommend using loadfiles for SQL as they are faster than inserts (meaning you would dump out your data to a file, and use a load query instead of running inserts)
Another method you can use with MySQL is as mentioned above by using INSERT ... SELECT
But that's a bit more of an advanced topic, since it's not the kind of query you'd see someone making a lot. Feel free to read the docs and give it a try!
I hope this at least begins to solve your problem. If I didn't cover something, something didn't make sense, or I didn't your question fully, please drop me a line and I'll do whatever I can to fix it for you.
This is how the query looks like: (simplified)
SELECT * FROM posts WHERE user='37' ORDER BY date DESC
I currently only ave one row in that table, but still for some reason it returns two rows that are exactly the same. At first i thought i messed up with the loop, but i tried printing the returned array out with print_r() and it actually returns two rows.
I tried searching, but i didn't find any similar issues. I do however remember that a friend of mine had the same issue at school, so i'm sure we aint the only ones. I probably just didn't use the right search terms, heh.
If you have only one record (verify this), it has to be application logic that is duplicating the returned values.
Are you sure you only have one row in the table? If so, it seems like the problem must be happening outside of SQL.
What are you doing outside of this query? That seems like the likely source of the issue. You mention a loop: could you be adding the query result to your array twice? Or is the array persisting between calls without being reinitialized (in other words, the result of a previous query is remaining in the array when you don't expect it to)?
limit 1 is your friend :)
Try adding it to the end of your query.