I have a table with a unique column 'a'. I want to add a row to it.
If the row I want to add has a 'a' value that is already in the table, then of course, due to the uniqueness of the column, it will not be added, else, it will be added. I need to check if the new row was added, which will then tell me if the 'a' value was already in the table or not.
Whats the most efficient way to check if the new entry has been added to the table or not?
EDIT - For measure, the worst case scenario so far is a count before and a count after...
I always use ON DUPLICATE KEY UPDATE for that (but I normally want to update rows when the unique key already exits...).
In PDO you can then get a return code with something like $stmt->rowCount() that gives a 1 for a new record and a 2 for an updated record.
I meant something like this (silly example)
$conn = mysql_connect('bla bla bla');
if (!mysql_query("insert into my_table values ('b')")) {
echo mysql_errno($conn) . ': ' . mysql_error($conn) . "\n";
}
else {
echo 'ok!';
}
Related
I try to write in DB table, but before I need check that the same var doesn't exist in column. But my code doesn't workd correctly for empty table. How to fix it to it start to work for empty table and later?
try
{
//$sql = "SELECT id FROM ".$table." WHERE ".$col." = :value";
$sql = "SELECT id FROM column WHERE name = :value";
$s = $pdo->prepare($sql);
$s->bindValue(':value', $value);
$relut = $s->execute();
verifyVarDump($relut, '$relut: ');
verifyVarDump($s, '$s: ');
foreach($s as $row)
{
echo ' :OK: ';
if(is_int($row['id']))
{
continue;
}
else
{
$valuesUnique[] = $value;
}
}
}
catch(PDOException $e)
{
echo 'Не удалось читать БД';
exit();
}
}
Tim's comment is what you need, but as you probably don't know what a "constraint" is, here are the steps (it's actually much simpler that what you are doing)
1) In your table definition: add either a primary key index, or a unique index. A little bit of light reading (https://dev.mysql.com/doc/refman/8.0/en/constraint-primary-key.html).
What this means is, if you try to add another entry with the same value, it will fail and throw and error. And you use this to your advantage.
2) You then add in the new row with "INSERT INTO" , and it'll fail if it the value exists in your "unique" column, or work if it doesn't. Simple. One query does it all :)
There are two other tricks you can do:
a) You can do a "REPLACE INTO" and that says "If the unique key does not exists, add in the new row; if it does exists then delete the row first and then add in my new one"
b) You can do a "INSERT INTO ..... ON DUPLICATE KEY UPDATE" and that says "If the unique key does not exists, add in the new row; if it does exists then modify the existing row with the UPDATES in the second half.
Two more single line queries that do all you need!
Good luck.
I've the following table layout in my database with some data.
I'm taking input by check-boxes so user can select all applicable accident road conditions and it to database. I would say it is okay if you're adding a new record you just loop through the checkboexs checked and insert them in DB
The first information is now saved in the database, now user decided to change the road conditions for any reasons user came back and change it the to the following.
Now my question, how should I update my table. The first thing that came into my mind was to delete the record that were already there and insert the new one's.
My real issue here is, assume user have choose the 3 items before but changed it two or one then how would i delete the those are not checked you know what I'm saying. Below is some code snippets that I've been trying.
$accidentRoadConditions = AccidentRoadConditions::findAccidentRoadConditions($acc_det_id);
$wc_array = [];
while ($roadConditions = $accidentRoadConditions ->fetch(PDO::FETCH_OBJ)) {
$wc_array[] = $roadConditions ->rc_id;
}
Above I'm selecting all the road conditions that is already stored in the database.
if (isset($_POST['rta_ad_rc'])) {
foreach ($_POST['rta_ad_rc'] as $rc_id) {
//AccidentRoadConditions::save(array(null, $ad_lsid, $rc_id));
// $tmprory = AccidentRoadConditions::findByADAndRCIds($acc_det_id, $rc_id);
// if(!$tmprory){
// AccidentRoadConditions::save(array(null, $acc_det_id, $rc_id));
// }
if(in_array($rc_id, $wc_array)){
$errors[] = "in array <br />";
unset($wc_array[0]);
}
}
}
So my question is how to update values in database according to what was checked by user and deleting those which were unchecked which were checked before. Getting bit complicated so simply how to update database according to above mention scenario.
Any Idea?
I think you need to do the following
Store the selected checks in an array
Check in the database if any of those are already saved or not
if yes, skipped them otherwise add them into an array
$old_rc_array = [];
$new_rc_array = [];
while ($roadConditions = $accidentRoadConditions->fetch(PDO::FETCH_OBJ)) {
$old_rc_array[] = $roadConditions->rc_id;
}
if (isset($_POST['rta_ad_rc'])) {
foreach ($_POST['rta_ad_rc'] as $rc_id) {
if(in_array($rc_id, $old_rc_array)){
unset($old_rc_array[array_search($rc_id, $old_rc_array)]);
}else{
$new_rc_array[] = $rc_id;
}
}
}
foreach ($old_rc_array as $rc_to_delete) {
AccidentRoadConditions::deleteByADIdAndRCId($hidden_acc_det_id, $rc_to_delete);
}
foreach ($new_rc_array as $rc_to_insert) {
AccidentRoadConditions::save(array(null, $hidden_acc_det_id, $rc_to_insert));
}
I think this is what you should do.
Create composite unique constraint on ad_id and rc_id
Delete all the rows not in the selected checkbox ids.
Try to insert all the rows but user INSERT IGNORE. This will insert the record if it does not exist or it will just ignore it. As you are using some framework see how you can do that.
If you can not then just wrap it using try/catch and ignore if the error is related to constraint violation.
This way You don't need to check if the values exist and also there will not be any unnecessary inserts.
I wrote a function which makes a random id makeid(); Just to ensure the id is unique I have a SQL statement which checks if the id already exists.
$does_id_exist = mysql_query("SELECT COUNT(*) AS count FROM signups WHERE affid='$affid'");
if(mysql_num_rows($does_id_exist) == 1)
{
#loop function and perform query again
}
else
{
#insert record
}
So I'm having trouble with looping the function. How do I loop my function makeid() and perform the $does_id_exist check to ensure that each ID is unique.
--UPDATE-- Just to clarify- My code makes an id like YES#281E But before I INSERT this id into the users record. I just need to verify IF any other user already has this id. IF another user has this id that event must trigger my function to create a new id e.g. WOW!29E3 and again check the sql/query to ensure no other user has that id. Continue to loop if fails or end and INSERT if the id is available.
You can either just use a primary key on your database table, or something like this:
<?php
// the id to insert
$newId = null;
// populate with results from a SELECT `aff_id` FROM `table`
$currentIds = array();
// prepopulate
for( $i=0; $i<100000; $i++ )
{
$currentIds[] = "STRING_" + rand();
}
// generate at least one id
do
{
$newId = "STRING_" + rand();
}
// while the id is taken (cached in $currentIds)
while( in_array($newId, $currentIds) );
// when we get here, we have an id that's not taken.
echo $newId;
?>
Output:
STRING_905649971 (run time 95ms);
I'd definitely not recommend running the query repeatedly. Perhaps a final check before you insert, if your traffic volume is high enough.
Do not do COUNT(*), because you do not need to know how many rows is there (it should be 0 or 1 as you need Id unique), so even DB finds your row it will still be checking for the whole table to count. You really care if you got 1 row, so just select for row with that ID and this sufficient. You should also avoid using rand() - this does not help as you see and you cannot predict how many loops you can do before you find "free slot". use something predictable, like date prefix, or prefix incremented each day. anything that would help you narrow the data set. But for now (pseudocode!):
$id = null;
while( $id == null ) {
$newId = 'prefix' . rand();
mysql_query("SELECT `affid` FROM `signups` WHERE `affid`='${newId}'");
if( mysql_num_rows() == 0) {
$id = newId;
break;
}
}
Ensure you got DB indexed, to speed things up.
EDIT: I do agree that any cache would be useful to speed things up (you can add it easily yourself based on #Josh example), still, I think this is fixing at wrong place. If possible rethink the way you generate your ID. It does not really need to be auto increment, but something more predictable than rand() would help you. If your ID does not need to be easily memorable and it is not any security concern to have them sequential, maybe use numbers with other base than 10 (i.e. using 26 would use all digits + letters so you'd end with PREFIX-AX3TK, so string as you want, and at the same time you would easily be able to quickly generate next Id
I know there are a lot of topics with the same title. But mostly it's the query that's been inserted in the wrong place. But I think I placed it right.
So the problem is, that I still get 0 even when the data is inserted in the db.
Does someone knows an answer where I could be wrong?
here's my code:
mysql_query('SET NAMES utf8');
$this->arr_kolommen = $arr_kolommen;
$this->arr_waardes = $arr_waardes;
$this->tabel = $tabel;
$aantal = count($this->arr_kolommen);
//$sql="INSERT INTO `tbl_photo_lijst_zoekcriteria` ( `PLZ_FOTO` , `PLZ_ZOEKCRITERIA`,`PLZ_CATEGORIE`)VALUES ('$foto', '$zoekje','$afdeling');";
$insert = "INSERT INTO ".$this->tabel." ";
$kolommen = "(";
$waardes = " VALUES(";
for($i=0;$i<$aantal;$i++)
{
$kolommen .=$this->arr_kolommen[$i].",";
$waardes .="'".$this->arr_waardes[$i]."',";
}
$kolommen = substr($kolommen,0,-1).")";
$waardes = substr($waardes,0,-1).")";
$insert .=$kolommen.$waardes;
$result = mysql_query($insert,$this->db) or die ($this->sendErrorToMail(str_replace(" ","",str_replace("\r\n","\n",$insert))."\n\n".str_replace(" ","",str_replace("\r\n","\n",mysql_error()))));
$waarde = mysql_insert_id();
Thanks a lot in advance, because I have been breaking my head for this one for almost already a whole day. (and probably it's something small and stupid)
According to the manual mysql_insert_id returns:
The ID generated for an AUTO_INCREMENT column by the previous query on
success, 0 if the previous query does not generate an AUTO_INCREMENT
value, or FALSE if no MySQL connection was established.
Since it does not give you false and not the correct number it indicates that the queried table didn't generate an auto-increment value.
There are two possibilities I can think of:
Your table doesn't have an auto_increment field
Since you doesn't provide the link to the mysql_insert_id() but using a link with mysql_query() it might not be the correct table that's queried when retrieving the last inserted id.
Solution:
Make sure it has an auto_increment field
Provide the link aswell: $waarde = mysql_insert_id($this->db);
It is possible that your INSERT query was not successful - e.g., maybe you were trying to insert duplicate data on a column whose data must be unique?
If the id is indeed set to auto increment and still get '0' as your response do a column and value count i experienced this only later on I noticed a number of my column count did not match values count.
Codeigniter has an odd behaviourd when calling mysql_insert_id(). The function returns 0 after the first call. So calling it twice will return 0.
Use a variable instead of calling the function more times:
$id = mysql_insert_id();
This refactor seems workable in my head, but I'd like someone to check my logic:
Current process:
if (item == new) {
INSERT INTO basic_table
$itemUID = get last insert ID // item's UID
INSERT INTO another_table // more stuff
INSERT INTO another_table2 // more stuff
INSERT INTO another_table3 // more stuff
} else {
$itemUID = $_POST['uid']
UPDATE basic_table
REPLACE INTO another_table // more stuff
REPLACE INTO another_table2 // more stuff
REPLACE INTO another_table3 // more stuff
}
(note - REPLACE INTO is used for existing items because they may or may not have entries in all the tables, depending on their initial configuration)
It occurred to me that since all the follow-on queries are identical except for INSERT INTO // REPLACE INTO, I should be able to refactor as:
if (item == new) {
INSERT INTO basic_table
$itemUID = get last insert ID // item's UID
} else {
$itemUID = $_POST['uid']
UPDATE basic_table
}
REPLACE INTO another_table // more stuff
REPLACE INTO another_table2 // more stuff
REPLACE INTO another_table3 // more stuff
Considering that I'm using PDO and each of those queries has lots of parameters, this would save a crapload of space.
But I wanted to post it here first, to make sure I'm not overlooking something.
Would this refactoring produce the same result?
If you don't care about the primary key changing, use REPLACE. If the key needs to remain consistent, as in, if it has been mapped to other tables, continue to use INSERT and UPDATE. REPLACE deletes and re-inserts so if your primary key is an auto_increment field it will change to the new increment value.