From the following Queries, Which one is the most optimal and fastest to use?
[COUNT(id)]
$SQL = "SELECT name, COUNT(id) as Count FROM names WHERE name = :name";
$row = $stmt->fetch();
if ($data['count'] > 0) {
while ($row) {
$name = $row['name'];
}
} else {
return;
}
OR [rowCount()]
$SQL = "SELECT name FROM names WHERE name = :name";
if ($stmt->rowCount() > 0) {
while ($row = $stmt->fetch()) {
$name = $row['name'];
}
} else {
return;
}
OR [EXISTS]
$SQLEX = "SELECT EXISTS (SELECT name FROM names WHERE name = :name LIMIT 1)";
if ($stmt->fetchColumn == 1) {
$SQL = "SELECT name FROM names WHERE name = :name";
while (row = $stmt->fetch()){
$name = $row['name'];
}
} else {
return;
}
OR [RAW]
$SQL = "SELECT name FROM names WHERE name = :name";
$row = $stmt->fetch();
if ($row) {
while($row) {
$name = $row['name'];
}
} else {
return;
}
Also i wanted to know, Why does using $stmt->fetch() with $stmt->rowCount() allows me to fetch data, But using it with $stmt->fetchColumn doesn't?
First, if you have an index on names(name), then all should be quite comparable in speed.
Second, it is always worth trying such performance tests on your own system.
Third, if names are declared as unique (or primary key) in the names table, then all should be quite fast.
In general, though, the fastest way to determine if a row is available is:
SELECT EXISTS (SELECT name FROM names WHERE name = :name)
The LIMIT 1 in the subquery is unnecessary -- EXISTS stops at the first row (whether the database uses an index or a table scan).
In general, the first method using an aggregation is the worst solution. Without an index, it is going to result in a full table scan that reads the entire table. The second might or might not read the entire table, depending on whether the database starts returning matching rows as they are available. It also has the downside of returning more data.
Ok, it seems this question needs more than one answer...
f you need to check the existence only,
if there is an unique index for the field, all methods are equal, but some of them just make no sense.
if there is no unique index, then go for EXISTS
If you need to fetch the actual data and see if there was anything returned, then just select your data and fetch it:
if only one column from a single row is expected, then use fetchColumn()
if only one row is expected, then use fetch()
if multiple rows are expected, then use fetchAll()
and then use the resulting value to see whether your query returned any data.
So if you finally made your mind as to what you're asking about, here is the most optimal code for you:
$SQL = "SELECT name FROM names WHERE name = :name";
$data = $stmt->fetchAll(PDO::FETCH_COLUMN);
if (!$data) {
return;
}
foreach ($data as $name) ...
And there is nothing wrong with fetchColumn() other than your idea to use it.
I am a novice when it comes to PHP but I don't understand if my syntax is wrong in this statement, or how would I grab an int from my MySQL server.
I know that my server credentials are working fine. How would I fix this statement to give me a returned integer of the number of reviews in the userinfo table?
$numberofpreviousreviews = mysql_query("SELECT `number_of_reviews` FROM `userinfo`") or die(mysql_error()); //Check to see how many reviews user has previously created
$amountofreviews = $numberofpreviousreviews + 1;
$query2 = mysql_query("ALTER TABLE userinfo ADD `amountofreviews` VARCHAR(10000)") or die(mysql_error()); //Make another column in database for the new review
You need to fetch your results after you run your query. There are several ways to do this but using mysql_fetch_assoc() will work for you.
$numberofpreviousreviews = mysql_query("SELECT `number_of_reviews` FROM `userinfo`") or die(mysql_error()); //Check to see how many reviews user has previously created
$row = mysql_fetch_assoc($numberofpreviousreviews);
$amountofreviews = $row['number_of_reviews'] + 1;
FYI, you shouldn't be using mysql_* functions anymore. They are deprecated and going away. You should use mysqli or PDO.
Assume you have a table userinfo which has the following structure and data :
Scenario #1 :
If you want to retrieve the all number_of_reviews, then do like this,
$query = "SELECT `number_of_reviews` FROM `userinfo`";
$result = mysqli_query($db,$query);
while ($row = mysqli_fetch_assoc($result)) {
echo "Number of reviews : " . $row['number_of_reviews'] . "<br/>";
}
It will give you,
Number of reviews : 20
Number of reviews : 40
Since, the result has many rows, it will display like above.
Scenario #2:
If you want to retrieve only the specific number_of_reviews for some user id (which is unique). I take id as 1 as a example here. Then do like,
$query2 = "SELECT `number_of_reviews` FROM `userinfo` WHERE `id` = 1";
$result2 = mysqli_query($db,$query2);
while ($row2 = mysqli_fetch_assoc($result2)) {
echo $row2['number_of_reviews'] . "<br/>";
}
This will print,
20.
Because, number_of_reviews is 20 for id 1.
I am trying to get the last value of a field during a new registration.
before insert data into the table, I want to create a user id number according to the last registered user's id number. to do that I use this:
//to reach the last value of userID field;
$sql = "SELECT userID FROM loto_users ORDER BY userID DESC LIMIT 1";
$result = mysql_query($sql);
while($row = mysql_fetch_array($result))
{
$value = $row['userID'];
echo "$value"; //not resulting here
}
$userID = $value+1;
so, the userID becomes 1.
The weird thing is, I could capable to use exact same code in another php file and works fine.
I would like to say that, rest of the code works fine. No problem with db connections or any other things you can tell me.
Note that: When I run the same query line in the mysql interface, I can get the value I want. I mean $sql line.
Your problem is in this code:
{
$svalue = $row['userID'];
----^
echo "$value"; //not resulting here
}
$userID = $value+1;
Change to $value.
But the right answer is to define userID to be auto-incrementing. That way, the database does the work for you. After inserting the row, you can do:
SELECT LAST_INSERT_ID()
To get the last value.
I solved the problem. Here;
$sql = "SELECT userID FROM loto_users ORDER BY userID DESC LIMIT 1";
$result = mysql_query($sql);
$user_info = $result->fetch_assoc();
$value = intval($user_info["userID"]);
$userID = $value+1;
Thanks everyone.
If you mark the userID field as autoincrement in you mysql table.
You won't need to set the userID and db increase the userID for you. You can get the assigned userID using the mysql_insert_id() function. Here is an example from php.net
mysql_query("INSERT INTO mytable (product) values ('kossu')");
printf("Last inserted record has id %d\n", mysql_insert_id());
Here is another example for your case
mysql_query("INSERT INTO 'loto_users'('username',...) values('usernameValue',...)");
echo "New User id is ".mysql_insert_id();
PHP newbie here
I have a mysql table called "topics", and i'm pulling information from the table for a page based on a result from a form (in the URL through GET)
If the URL doesn't exist, i'd like to be able for the table to create a new entry with the topic name from the URL filled in
$topic_name would be what i'd be putting in the new topicname field
My code so far:
$topic_name = strtolower(mysql_real_escape_string($_GET['t']));
//look for info
$topic_info = mysql_query("SELECT * FROM topics WHERE topicname = '$topic_name' LIMIT 1");
if (mysql_numrows($topic_info)<=0) {
//insert record
$SQL='insert into topics (topicname) values ("'.$topic_name.'")';
mysql_query($SQL);
$t_desc='NEW TOPIC : '.$topic_name;
}
else {
//do as normal (without unnessecary loop)
$g=mysql_fetch_array($topic_info);
$t_desc = $g['desc'];
}
EDIT: Sorry, I don't think i explained well, the result is from a GET from a form, so url.com/topic?=BLAH
blah would be the name of the field i'd want to create if it doesn't exist.
The table has an Auto incrementing 'ID' (primary key)
If i understand you correct :
$topic_name = (isset($_GET['t'])) ? strtolower(mysql_real_escape_string($_GET['t'])) : '';
//look for info
$topic_info = mysql_query("SELECT * FROM topics WHERE topicname = '$topic_name' LIMIT 1");
if (mysql_num_rows($topic_info)<=0) {
//insert record
//UPDATE
//$SQL='insert into topics (topicname) values ("'.$topic_name.'")';
$SQL='insert into topics (topicname, `desc`) values '.
'("'.$topic_name.'", "NEW TOPIC DESC")';
mysql_query($SQL);
$t_desc='NEW TOPIC : '.$topic_name;
} else {
//do as normal (without unnessecary loop)
$g=mysql_fetch_array($topic_info);
$t_desc = $g['desc'];
}
Try as below
$topic_info = mysql_query("SELECT * FROM topics WHERE topicname = '$topic_name' LIMIT 1");
$count = mysql_num_rows($topic_info);
if($count <= 0){
// do insert query
}
else {
// loop through you result and display record
while($g = mysql_fetch_array($topic_info)){
$t_desc = $g['desc'];
}
}
Note: Better to use PDO or Mysqli lib for new development and prevent mysql injection attack
What's the best way with PHP to read a single record from a MySQL database? E.g.:
SELECT id FROM games
I was trying to find an answer in the old questions, but had no luck.
This post is marked obsolete because the content is out of date. It is not currently accepting new interactions.
$id = mysql_result(mysql_query("SELECT id FROM games LIMIT 1"),0);
$link = mysql_connect('localhost','root','yourPassword')
mysql_select_db('database_name', $link);
$sql = 'SELECT id FROM games LIMIT 1';
$result = mysql_query($sql, $link) or die(mysql_error());
$row = mysql_fetch_assoc($result);
print_r($row);
There were few things missing in ChrisAD answer. After connecting to mysql it's crucial to select database and also die() statement allows you to see errors if they occur.
Be carefull it works only if you have 1 record in the database, because otherwise you need to add WHERE id=xx or something similar to get only one row and not more. Also you can access your id like $row['id']
Using PDO you could do something like this:
$db = new PDO('mysql:host=hostname;dbname=dbname', 'username', 'password');
$stmt = $db->query('select id from games where ...');
$id = $stmt->fetchColumn(0);
if ($id !== false) {
echo $id;
}
You obviously should also check whether PDO::query() executes the query OK (either by checking the result or telling PDO to throw exceptions instead)
Assuming you are using an auto-incrementing primary key, which is the normal way to do things, then you can access the key value of the last row you put into the database with:
$userID = mysqli_insert_id($link);
otherwise, you'll have to know more specifics about the row you are trying to find, such as email address. Without knowing your table structure, we can't be more specific.
Either way, to limit your SELECT query, use a WHERE statement like this:
(Generic Example)
$getID = mysqli_fetch_assoc(mysqli_query($link, "SELECT userID FROM users WHERE something = 'unique'"));
$userID = $getID['userID'];
(Specific example)
Or a more specific example:
$getID = mysqli_fetch_assoc(mysqli_query($link, "SELECT userID FROM users WHERE userID = 1"));
$userID = $getID['userID'];
Warning! Your SQL isn't a good idea, because it will select all rows (no WHERE clause assumes "WHERE 1"!) and clog your application if you have a large number of rows. (What's the point of selecting 1,000 rows when 1 will do?) So instead, when selecting only one row, make sure you specify the LIMIT clause:
$sql = "SELECT id FROM games LIMIT 1"; // Select ONLY one, instead of all
$result = $db->query($sql);
$row = $result->fetch_assoc();
echo 'Game ID: '.$row['id'];
This difference requires MySQL to select only the first matching record, so ordering the table is important or you ought to use a WHERE clause. However, it's a whole lot less memory and time to find that one record, than to get every record and output row number one.
One more answer for object oriented style. Found this solution for me:
$id = $dbh->query("SELECT id FROM mytable WHERE mycolumn = 'foo'")->fetch_object()->id;
gives back just one id. Verify that your design ensures you got the right one.
First you connect to your database. Then you build the query string. Then you launch the query and store the result, and finally you fetch what rows you want from the result by using one of the fetch methods.
$link = mysql_connect('localhost','root','yourPassword')
mysql_select_db('database',$link);
$sql = 'SELECT id FROM games'
$result = mysql_query($sql,$link);
$singleRow = mysql_fetch_array($result)
echo $singleRow;
Edit: So sorry, forgot the database connection. Added it now
'Best way' aside some usual ways of retrieving a single record from the database with PHP go like that:
with mysqli
$sql = "SELECT id, name, producer FROM games WHERE user_id = 1";
$result = $db->query($sql);
$row = $result->fetch_row();
with Zend Framework
//Inside the table class
$select = $this->select()->where('user_id = ?', 1);
$row = $this->fetchRow($select);
The easiest way is to use mysql_result.
I copied some of the code below from other answers to save time.
$link = mysql_connect('localhost','root','yourPassword')
mysql_select_db('database',$link);
$sql = 'SELECT id FROM games'
$result = mysql_query($sql,$link);
$num_rows = mysql_num_rows($result);
// i is the row number and will be 0 through $num_rows-1
for ($i = 0; $i < $num_rows; $i++) {
$value = mysql_result($result, i, 'id');
echo 'Row ', i, ': ', $value, "\n";
}
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
$db = new mysqli('localhost', 'tmp', 'tmp', 'your_db');
$db->set_charset('utf8mb4');
if($row = $db->query("SELECT id FROM games LIMIT 1")->fetch_row()) { //NULL or array
$id = $row[0];
}
I agree that mysql_result is the easy way to retrieve contents of one cell from a MySQL result set. Tiny code:
$r = mysql_query('SELECT id FROM table') or die(mysql_error());
if (mysql_num_rows($r) > 0) {
echo mysql_result($r); // will output first ID
echo mysql_result($r, 1); // will ouput second ID
}
Easy way to Fetch Single Record from MySQL Database by using PHP List
The SQL Query is SELECT user_name from user_table WHERE user_id = 6
The PHP Code for the above Query is
$sql_select = "";
$sql_select .= "SELECT ";
$sql_select .= " user_name ";
$sql_select .= "FROM user_table ";
$sql_select .= "WHERE user_id = 6" ;
$rs_id = mysql_query($sql_select, $link) or die(mysql_error());
list($userName) = mysql_fetch_row($rs_id);
Note: The List Concept should be applicable for Single Row Fetching not for Multiple Rows
Better if SQL will be optimized with addion of LIMIT 1 in the end:
$query = "select id from games LIMIT 1";
SO ANSWER IS (works on php 5.6.3):
If you want to get first item of first row(even if it is not ID column):
queryExec($query) -> fetch_array()[0];
If you want to get first row(single item from DB)
queryExec($query) -> fetch_assoc();
If you want to some exact column from first row
queryExec($query) -> fetch_assoc()['columnName'];
or need to fix query and use first written way :)