PHP + SQLite duplicate inserts - php

Every insert I do happens twice.
I thought the page might be getting hit twice so I also added a counter file that would increment on each load. The page is only getting hit once, yet each insert is inserted twice.
<?
$x = intval(file_get_contents("./count.x"));
header("Content-type: text/plain");
$db = new SQLite3("/var/www/images/cache.db");
$statement = $db->prepare('insert into `imgCache` (name,type,data) values("test7","bmp","argh);');
$result = $statement->execute();
while ($row = $result->fetchArray(SQLITE3_ASSOC))
{
print_r($row);
}
$x++;
file_put_contents("./count.x",$x);
?>
Prior to running this script there is no entry for "test7" in the database, and the contents of count.x is "0".
When I run this script, the following happens
count.x contains the text "1"
there are TWO entries for test7 in the database now.

PHP executes queries twice: one time to check whether any rows are returned, and a second time to actually return the rows.
An INSERT statement is not a query, and does not return rows.
Remove the fetchArray call.

Related

sqlsrv_execute doesn't return anything

I'm using the SQL Server drivers for PHP to access a SQL Server database and I have a problem to update some data using sqlsrv_prpare and sqlsrv_execute functions.
I'm running two queries:
In the first query I'm retrieving some binary data (In SQL Server Management Studio, this query takes about 15 minutes to getting completed);
Then, for each row returned by the first query execution I'm trying to Update some data on the database.
Here's how my code looks like:
$query1 = "SELECT tgt.id, src.file, src.field1 from [Table1] tgt inner join [Table2] src on tgt.id = src.id order by tgt.id";
$query2 = "UPDATE [Table1] SET field1 = ? WHERE id = ?";
$getFiles = sqlsrv_query($con, $query1); //$con is the connection with the database, received by parameter
while($row = sqlsrv_fetch_array($getFiles, SQLSRV_FETCH_BOTH)) {
/* Some code here */
$file = $row[1];
$value = $row[2];
try {
if(!is_null($file)) {
$stmt = sqlsrv_prepare($con, $query2, array(&$value, &$row[0]));
if( $stmt === false ) {
die( print_r( sqlsrv_errors(), true));
}
sqlsrv_execute( $stmt );
}
} catch (Exception $e) {
error_log("\nError: " . $e->getMessage());
}
} //end while
sqlsrv_free_stmt($getFiles);
sqlsrv_close($con);
The problem is that the code inside the loop works fine to the first row, but on the second the update query isn't executed. The sqlsrv_prepare returns the value 1, but the sqlsrv_execute doesn't returns anything.
I'm thinking that the problem could be related to the first query execution time, but I don't know how to check this, considering that no error log is generated, the script just keeps executing forever.
EDIT: Actually, the example was simplified. The values that will be updated on tgt table are calculated using some data that are in src table and other application data. That's the reason why I use the loop, for each row returned by query1 specific values are calculated and used on query2. I already checked that these values are correctly calculated, this is why I thought it's better to simplify the example.
To solve this problem I have to ran the queries separately:
First I ran the query1, made the computation of the data that I needed to update the tgt table and stored them in an array;
Then, using the data stored in array, I ran the query2.
No other changes were needed.

Explanation of mysqli_fetch_array and foreach

<?php
$connect = mysqli_connect("localhost", "root", "", "hempbag_db") or die("Connection failed");
$query= "Select * from tbl_sales";
$ress = mysqli_query($connect, $query);
$result = mysqli_fetch_array($ress);
foreach($result as $a)
{
echo $a['ID']; // This doesnt print although i used fetch array
}
foreach($ress as $a)
{
echo $a['ID']; // This works why???? This variable has only query run
}
?>
Why does the upper foreach does not run and lower one does? Can anyone explain please?
When you run a query, it returns a result:
$ress = mysqli_query($connect, $query);
var_dump($ress); // You will see it's a result.
At this point $ress just contains the result of what you just queried. Think of it like this:
You goto the warehouse, and you make and order for 1000 boxes of crackers. She heads to the back, and gets your boxes ready, and comes back and hands you a piece of paper with the order number. (This is $ress). Now, you can't loop through that, you can't do anything with that.
You now take that piece of paper, and you hand it to your assistant, and you say you want to get all the crackers on your trucks (This is now mysqli_fetch_array()). Your assistant goes, fetches it, and returns you the crackers.
Simply put, mysqli_query just returns an object like Result#1. From Result#1, mysql can tell you how many rows were returned mysql_num_rows(Result#1), or get actual data if it was a select query: mysqli_fetch_array(Result#1).
Now onto the reasoning: Performance. Let's say you didn't want 1000 crackers, you just wanted to know if they had 1000 crackers. If she came back with all the boxes of crackers and you had to count them yourself, it would be much more difficult. Instead, with that piece of paper, she can determine how many boxes you were able to order. Less data being transferred, and much more efficient.
Just a small note, in later versions of php, they made it so the result is iterable, meaning that if you try and loop through it, it will automagically call mysqli_fetch_array on that result, and return you the results.
Additionally, mysql_fetch_array will return one row from the database, and is not able to be looped through via foreach. Perhaps you were thinking of mysqli_fetch_all? This returns all rows and can be looped through (Although is a bit less performant than using a while loop with mysqli_fetch_array)
$ress = mysqli_query($connect, $query);
This line returns a result set which is Traversable. So your second foreach works fine.
whereas the following line (mysqli_fetch_array) gets one row at a time and makes it an array.
$result = mysqli_fetch_array($ress); // Suppose you have 3 rows, Now cursor is at row 1
echo $result["ID"]; // this will print FIRST row's ID
$result = mysqli_fetch_array($ress); // Now cursor is at row 2
echo $result["ID"]; // this will print SECOND row's ID.
$result = mysqli_fetch_array($ress); // Now cursor is at row 3
echo $result["ID"]; // this will print THIRD row's ID.
To echo all IDs
while($result = mysqli_fetch_array($ress)) {
echo $result["ID"];
}

PHP PDO sqlsrv large result set inconsistency

I am using PDO to execute a query for which I am expecting ~500K results. This is my query:
SELECT Email FROM mytable WHERE flag = 1
When I run the query in Microsoft SQL Server management Studio I consistently get 544838 results. I wanted to write a small script in PHP that would fetch these results for me. My original implementation used fetchAll(), but this was exhausting the memory available to php, so I decided to fetch the results one at a time like so:
$q = <<<QUERY
SELECT Email FROM mytable WHERE flag = 1
QUERY;
$stmt = $conn->prepare($q);
$stmt->execute();
$c = 0;
while ($email = $stmt->fetch()[0]) {
echo $email." $c\n";
$c++;
}
but each time I run the query, I get a different number of results! Typical results are:
445664
445836
445979
The number of results seems to be short 100K +/- 200 ish. Any help would be greatly appreciated.
fetch() method fetches one row at a time from current result set. $stmt->fetch()[0] is the first column of the current row.
Your sql query has no ordering and can have some null or empty values (probably).
Since you are controlling this column value in while loop, if the current row's first value is null, it will exit from the loop.
Therefore, you should control only fetch(), not fetch()[0] or something like that.
Also, inside the while loop, use sqlsrv_get_field() to access the columns by index.
$c = 0;
while ($stmt->fetch()) { // You may want to control errors
$email = sqlsrv_get_field($stmt, 0); // get first column value
// $email can be false on errors
echo $email . " $c\n";
$c++;
}
sqlsrv_fetch

How to get next row of MySQL query in php without progressing when using mysqli_fetch_assoc()

I am trying to run a query to my mysql database through php and and am trying to get all the resulting rows. I also have to compare every row to the next row returned. I am trying to do this by setting the result variable to another temporary variable and calling mysqli_fetch_assoc() on that so that the while loop runs again for the next row. But what happens is that when I try to use mysqli_fetch_assoc() even on the other variables, somehow mysqli_fetch_assoc($result) also progresses to the next of the next row when while($row = mysqli_fetch_assoc($result)) goes to next iteration.
Here is the code example to illustrate this :
$query = "SELECT * FROM records ORDER BY num ASC;";
if($result = mysqli_query($conn, $query))
{
while($row = mysqli_fetch_assoc($result))
{
$temporaryresult = $result;
$rowtwo = mysqli_fetch_assoc($temporaryresult);// this makes mysqli_fetch_assoc($result) skip the next row which is unwanted
}
}
So how can I keep mysqli_fetch_assoc($result) from moving forward when I call mysqli_fetch_assoc($temporaryresult) ?
Any help would be appreciated.
am trying to do this by setting the result variable to another temporary variable and calling mysqli_fetch_assoc() on that so that the while loop runs again for the next row
It doesn’t work that way. Just because you assigned the resource id to a second variable, doesn’t mean that you now have a second result set that you could operate on separately. Both variables refer to the same resource id. Fetching a row will still move the row pointer of the “original” data set.
I also have to compare every row to the next row returned
Most likely, you are making things harder on yourself by trying to look ahead. Stuff like this is usually easier done when you look at the previous row instead. That one you have fetched already - so you don’t need to do an additional fetch now that would mess with the row pointer.
Pseudo code example:
$prevRow = null;
while($row = fetch(...)) {
if($prevRow) { // for the first row, this will still be null, so we only
// start comparing stuff when that is not the case
// compare whatever you need to compare here
}
...
$prevRow = $row;
}
After #CBroe's answer, I tried to solve this problem while still trying to look forward. I achieved this by storing the rows returned by the database and then looping through them. This makes it very easy too look ahead in the rows returned while avoiding the complexity of changing your code to look backwards.
$array = array();
// look through query
while($row = mysql_fetch_assoc($query)){
// add each row returned into an array
$array[] = $row;
}
Now, looping through these rows,
$i = 0;
for(;$i<count($array)-1;$i++)
{
if($array[$i]['somecolumn']==$array[$i+1]['anothercolumn'])//compare this column to another column in the next row
{
// do something
}
}
This successfully solved my problem. I hope it helps anyone stuck in the same position I was in.

Transform MySQL table and rows

I have one problem here, and I don't even have clue what to Google and how to solve this.
I am making PHP application to export and import data from one MySQL table into another. And I have problem with these tables.
In source table it looks like this:
And my destination table has ID, and pr0, pr1, pr2 as rows. So it looks like this:
Now the problem is the following: If I just copy ( insert every value of 1st table as new row in second) It will have like 20.000 rows, instead of 1000 for example.
Even if I copy every record as new row in second database, is there any way I can fuse rows ? Basically I need to check if value exists in last row with that ID_, if it exist in that row and column (pr2 for example) then insert new row with it, but if last row with same ID_ does not have value in pr2 column, just update that row with value in pr2 column.
I need idea how to do it in PHP or MySQL.
So you got a few Problems:
1) copy the table from SQL to PHP, pay attention to memory usage, run your script with the PHP command Memory_usage(). it will show you that importing SQL Data can be expensive. Look this up. another thing is that PHP DOESNT realese memory on setting new values to array. it will be usefull later on.
2)i didnt understand if the values are unique at the source or should be unique at the destination table.. So i will assume that all the source need to be on the destination as is.
I will also assume that pr = pr0 and quant=pr1.
3) you have missmatch names.. that can also be an issue. would take care of that..also.
4) will use My_sql, as the SQL connector..and $db is connected..
SCRIPT:
<?PHP
$select_sql = "SELECT * FROM Table_source";
$data_source = array();
while($array_data= mysql_fetch_array($select_sql)) {
$data_source[] = $array_data;
$insert_data=array();
}
$bulk =2000;
foreach($data_source as $data){
if(isset($start_query) == false)
{
$start_query = 'REPLACE INTO DEST_TABLE ('ID_','pr0','pr1','pr2')';
}
$insert_data[]=implode(',',$data).',0)';// will set 0 to the
if(count($insert_data) >=$bulk){
$values = implode('),(',$insert_data);
$values = substr(1,2,$values);
$values = ' VALUES '.$values;
$insert_query = $start_query.' '.$values;
$mysqli->query($insert_query);
$insert_data = array();
} //CHECK THE SYNTAX IM NOT SURE OF ALL OF IT MOSTLY THE SQL PART>> SEE THAT THE QUERY IS OK
}
if(count($insert_data) >=$bulk) // IF THERE ARE ANY EXTRA PIECES..
{
$values = implode('),(',$insert_data);
$values = substr(1,2,$values);
$values = ' VALUES '.$values;
$insert_query = $start_query.' '.$values;
$mysqli->query($insert_query);
$insert_data = null;
}
?>
ITs off the top off my head but check this idea and tell me if this work, the bugs night be in small things i forgot with the QUERY structure, print this and PASTE to PHPmyADMIN or you DB query and see its all good, but this concept will sqve a lot of problems..

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