I have the following sql statement written in PHP.
$sql='INSERT INTO pictures (`picture`) VALUES ("'.$imgs[$i]['name'].'",)';
$db->query($sql);
$imgs[$i]['sqlID'] = $this->id=mysql_insert_id();
$imgs[$i]['newImgName'] = $imgs[$i]['sqlID'].'_'.$imgs[$i]['name'];
$sql='UPDATE pictures SET picture="'.$imgs[$i]['newImgName'].'" WHERE id='.$imgs[$i]['sqlID'];
$db->query($sql);
Now this writes the image name to database table pictures. After that is done I get the mysql_insert_id() and than I'll update the picture name with the last id in front of the name with underscore.
I'll do this to make sure no picture name can be the same. Cause all those pictures get saved in the same folder. Is there another way to save that ID already the first time I set the sql query? Or are there other better ways to achieve this result?
Thanks for all advices
Using the native auto_increment - there is no other way. You need to do the 3 steps you described.
As Dan Bracuk mentioned, you can create a stored proc to do the 3 queries (you can still get the insert id after executing it).
Other possible options are:
not storing the id in the filename - you can concatenate it later if you want (when selecting)
using an ad-hoc auto increment instead of the native one - I would not recommend it in this case, but it's possible
using some sort of UUID instead of auto increment
generating unique file names using the file system (Marcell Fülöp's answer)
I don't think in this particular case it's reasonable to use MySQL insert Id in the file name. It might be required in some cases but you provided no information why it would be in this one.
Consider something like:
while( file_exists( $folder . $filename ) {
$filename = rand(1,999) . '_' . $filename;
}
$imgs[$i]['newImgName'] = $filename;
Of course you can use a larger range for rand or a loop counter if you wanted tot systematically increment the number used to prefix the original file name.
Related
I need a query that goes through each entry in a database, checks if a single value is duplicated elsewhere in the database, and if it is - deletes both entries (or all, if more than two).
Problem is the entries are URLs, up to 255 characters, with no way of identifying the row. Some existing answers on Stack Overflow do not work for me due to performance limitations, or they use uniqueid which obviously won't work when dealing with a string.
Long Version:
I have two databases containing URLs (and only URLs). One database has around 3,000 urls and the other around 1,000.
However, a large majority of the 1,000 urls were taken from the 3,000 url database. I need to merge the 1,000 into the 3,000 as new entries only.
For this, I made a third database with combined URLs from both tables, about 4,000 entries. I need to find all duplicate entries in this database and delete them (Both of them, without leaving either).
I have followed the query of a few examples on this site, but whenever I try to delete both entries it ends up deleting all the entries, or giving sql errors.
Alternatively:
I have two databases, each containing the separate database. I need to check each row from one database against the other to find any that aren't duplicates, and then add those to a third database.
Since you were looking for a SQL solution here is one. Lets assume that your table has a single column for simplicity sake. However this will work for any number of fields of course:
CREATE TABLE `allkindsofvalues` (
`value` int(11) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
The following series of queries will accomplish what you are looking for:
CREATE TABLE allkindsofvalues_temp LIKE allkindsofvalues;
INSERT INTO allkindsofvalues_temp SELECT * FROM allkindsofvalues akv1 WHERE (SELECT COUNT(*) FROM allkindsofvalues akv2 WHERE akv1.value = akv2.value) = 1;
DROP TABLE allkindsofvalues;
RENAME TABLE allkindsofvalues_temp to allkindsofvalues;
The OP wrote:
I've got my own PHP solution which is pretty hacky, but works.
I went with a PHP script to accomplish this, as I'm more familiar with PHP than MySQL.
This generates a simple list of urls that only exist in the target
database, but not both. If you have more than 7,000 entries to parse
this may take awhile, and you will need to copy/paste the results
into a text file or expand the script to store them back into a
database.
I'm just doing it manually to save time.
Note: Uses MeekroDB
<pre>
<?php
require('meekrodb.2.1.class.php');
DB::$user = 'root';
DB::$password = '';
DB::$dbName = 'testdb';
$all = DB::query('SELECT * FROM old_urls LIMIT 7000');
foreach($all as $row) {
$test = DB::query('SELECT url FROM new_urls WHERE url=%s',
$row['url']);
if (!is_array($test)) {
echo $row['url'] . "\n";
}else{
if (count($test) == 0) {
echo $row['url'] . "\n";
}
}
}
?>
</pre>
I am using DBIx::Class and I would like to only update one row in my table. Currently this is how I do it:
my $session = my_app->model("DB::Session")->find(1);
$session->update({done_yn=>'y',end_time=>\'NOW()'});
It works, but the problem is that when it does find to find the row, it does this whole query:
SELECT me.id, me.project_id, me.user_id, me.start_time, me.end_time, me.notes, me.done_yn FROM sessions me WHERE ( me.id = ? ): '8'
Which seems a bit much when all I want to do is update a row. Is there anyway to update a row without having to pull the whole row out of the database first? Something like this is what I am looking for:
my_app->model("DB::Session")->update({done_yn=>'y',end_time=>\'NOW()'},{id=>$id});
Where $id is the WHERE id=? part of the query. Does anyone know how to do this? Thanks!
You can run update on a restricted resultset which only matches this single row:
my_app->model("DB::Session")->search_rs({ id=> 1 })->update({done_yn=>'y',end_time=>\'NOW()'});
I suggest you use a DateTime->now object instead of literal SQL for updating the end_time column because it uses the apps servers date and time instead of the database servers and makes your schema more compatible with different RDBMSes.
Do you have a check if the row was found to prevent an error in case it wasn't?
You might want to use update_or_create instead.
You could use the "columns" attribute:
my $session = my_app->model("DB::Session")->find(1, {columns => "id"});
1st I'll give you the query, and then I'll tell you what I am trying to achieve, as I could be soo wrong or soo close.
mysql_query("UPDATE link_building SET
ID=$ID,Site=$Site,Date=$Date,Target_Site=$Target_Site,
Target_Contact_Email=$Target_Contact_Email,
Target_Contact_Name=$Target_Contact_Name,
Link_Type=$Link_Type,Link_Acquired=$Link_Acquired,
Notes=$Notes,Link_URL=$Link_URL WHERE ID=" . $ID);
What am I trying to achieve?
I want to update the fields
("ID","Site","Date","Target_Site","Target_Contact_Email","Target_Contact_Name",
"Link_Type","Link_Acquired","Notes","Link_URL")
in the table link_building with the values stored in the variables
("$ID","$Site","$Date","$Target_Site","$Target_Contact_Email","$Target_Contact_Name",
"$Link_Type","$Link_Acquired","$Notes","$Link_URL")
But I only want to update the record whos Id is equal to $ID.
UPDATE: I DO NOT SEE ANY ERROR. ITS REDIRECTS TO link_building.php and displays success message but doesn't change the data in the MySQL table.
Try escaping the data and removing the update of the ID since its already in your conditions:
mysql_query("UPDATE link_building SET Site='".mysql_real_escape_string($Site)."',Date='".mysql_real_escape_string($Date)."',Target_Site='".mysql_real_escape_string($Target_Site)."', Target_Contact_Email='".mysql_real_escape_string($Target_Contact_Email)."', Target_Contact_Name='".mysql_real_escape_string($Target_Contact_Name)."', Link_Type='".mysql_real_escape_string($Link_Type)."',Link_Acquired='".mysql_real_escape_string($Link_Acquired)."', Notes='".mysql_real_escape_string($Notes)."',Link_URL='".mysql_real_escape_string($Link_URL)."' WHERE ID=" . intval($ID));
For one, you're forgetting that you still need to quote your strings;
mysql_query("UPDATE link_building SET Site='$Site', Date='$Date',".
"Target_Site='$Target_Site', Target_Contact_Email='$Target_Contact_Email',".
"Target_Contact_Name='$Target_Contact_Name', Link_Type='$Link_Type',".
"Link_Acquired='$Link_Acquired', Notes='$Notes', Link_URL='$Link_URL' ".
"WHERE ID=$ID");
Note the added 's around all strings.
Bonus remark; you should really be using mysql_real_escape_string() on your strings before passing them on to the database.
if your columns are named like Target Site (with a space in it), you should adress it like that in your query (wich will force you to add backticks to it). also, you'll have to add quotes to colums that store anything else that strings. your query should look like:
UPDATE
link_building
SET
ID = $ID,
Site = '$Site', // single quotes for values
Date = '$Date', // ...
´Target Site´ = '$Target_Site' // and ´ for fields
[...]
this should solve why the query doesn't work (in addition: not how a bit or formatting makes it much more readable).
you havn't given information about that, but please note that you should always sanitize your variables before using it (your code doesn't look like you do) to avoid sql-injections. you can do this using mysql_real_escape_string or, even better, start using prepared statements.
I am trying to take information out of a MySQL database, which I will then manipulate in perl:
use strict;
use DBI;
my $dbh_m= DBI->connect("dbi:mysql:Populationdb","root","LisaUni")
or die("Error: $DBI::errstr");
my $Genotype = 'Genotype'.1;
#The idea here is eventually I will ask the database how many Genotypes there are, and then loop it round to complete the following for each Genotype:
my $sql =qq(SELECT TransNo, gene.Gene FROM gene JOIN genotypegene ON gene.Gene = genotypegene.Gene WHERE Genotype like '$Genotype');
my $sth = $dbh_m-> prepare($sql);
$sth->execute;
my %hash;
my $transvalues = $sth->fetchrow_hashref;
my %hash= %$transvalues;
$sth ->finish();
$dbh_m->disconnect();
my $key;
my $value;
while (($key, $value) = each(%hash)){
print $key.", ".$value\n; }
This code doesn't produce any errors, but the %hash only stores the last row taken from the database (I got the idea of writing it this way from this website). If I type:
while(my $transvalues = $sth->fetchrow_hashref){
print "Gene: $transvalues->{Gene}\n";
print "Trans: $transvalues->{TransNo}\n";
}
Then it does print off all the rows, but I need all this information to be available once I've closed the connection to the database.
I also have a related question: in my MySQL database the row consists of e.g 'Gene1'(Gene) '4'(TransNo). Once I have taken this data out of the database as I am doing above, will the TransNo still know which Gene it is associated with? Or do I need to create some kind of hash of hash structure for that?
You are calling the "wrong" function
fetchrow_hashref will return one row as a hashref, you should wrap it's use inside a loop, ending it when fetchrow_hashref returns undef.
It seems like you are looking for fetchall_hashref, that will give you all of the returned rows as a hash with the first parameter specified what field to use as a key.
$hash_ref = $sth->fetchall_hashref ($key_field);
Each row will be inserted into $hash_ref as an internal hashref, using $key_field as the key in which you can find the row in $hash_ref.
What does the documentation say?
The fetchall_hashref method can be used to fetch all the data to be returned from a prepared and executed statement handle.
It returns a reference to a hash containing a key for each distinct value of the $key_field column that was fetched.
For each key the corresponding value is a reference to a hash containing all the selected columns and their values, as returned by fetchrow_hashref().
Documentation links
DBI - search.cpan.org #fetchrow_hashref
DBI - search.cpan.org #fetchall_hashref
This question already has an answer here:
If url already exists in url table in mysql. Break operation in php script
(1 answer)
Closed 9 months ago.
I have a varchar(255) column where I store URL's in a MySQL database. This column has a unique index.
When my crawler encounters a URL, it has to check the database to see if that URL already exists. If it exists, the crawler selects data about that entry. If it does not exist, the crawler adds the url. I currently do this with the following code:
$sql = "SELECT id, junk
FROM files
WHERE url = '$url'";
$results = $this->mysqli->query( $sql );
// the file already exists in the system
if( $results->num_rows > 0 )
{
// store data to variables
}
// the file does not exists yet... add it
else
{
// insert new file
$sql = "INSERT INTO files( url )
VALUES( '$url' )";
$results = $this->mysqli->query( $sql );
}
I realize there are lots of ways to do this. I've read that using a MySQL if/else statement could speed this up. Can someone explain how MySQL would handle that differently, and why that may be faster? Are there other alternatives I should test? My crawlers are doing a lot of checking like this, and speeding up this process could be a significant speed boost for my system.
First of all, URLs are going to get much longer than varchar(256).
Second of all, because they're that long you don't want to do string compares, it gets very slow as the table grows. Instead, create a column with a hash value and compare that.
You should index the hash column, of course.
As for the actual insert, an alternative is to put a unique constraint on the hash. Then do your inserts blindly, allowing SQL to reject the dupes. (But you'll have to put an exception handler into your code, which has its own overhead.)
Considering not using transactions, to insert a new row if an old row does not exist by the WHERE condition, you can use:
"INSERT INTO files( url ) VALUES ( $url ) WHERE NOT EXISTS ( SELECT * FROM files WHERE url = $url );"
I can't think of a "one-line-commond" to select and insert at the same time.
I would do the insert first and check for success(affected_rows), then select. If you check first, and then do the insert, the possibility exists that the url got inserted during that small time window. And, you would need to add more code to handle this situation.