I want to fetch data from a database until a certain condition is satisfied. If this condition is satisfied I want to stop fetching after that point.
while($row=mysql_fetch_array($result1)){
$a1=$row['Count']
if($a1<100){
$w1=$a1
//Now I want to stop fetching data after this point and take the variable "$w1" out
}
You can use break:
while ($row = mysql_fetch_array($result1)) {
$a1 = $row['Count'];
if ($a1 < 100) {
$w1 = $a1;
break;
}
}
Or return it out of a function.
Best option is to give limits and where condition in your query
So that the query execution will be fast (You need to fetch less data).
Instead of fetching whole the data first and filtering it, Filter the data first and fetch it.
In your case : if you want to fetch first 100 records :
$sql = "SELECT * FROM table LIMIT 0,100";
And if you have any condition then,
$sql = "SELECT * FROM table WHERE field = '".$var."' LIMIT 0,100";
Use break; or better you can use limit & where condition in your query
while($row=mysql_fetch_array($result1))
{
$a1=$row['Count'];
if($a1<100)
{
$w1=$a1; break;
}
}
Related
hi i have a backend with php in cpanel and i have a problem with one of jsons . this is part of my php code :
...
}elseif ($work == "dollardate") {
$query3 = "SELECT * FROM tabl_dollar_date";
$result3 = $connect->prepare($query3);
$result3->execute();
$out3 = array();
while ($row3 = $result3->fetch(PDO::FETCH_ASSOC)) {
$record3 = array();
$record3["dollar"] = $row3["dollar"];
$record3["date"] = $row3["date"];
array_push($out3, $record3);
}
echo json_encode($out3);
}
?>
this code show this in json :
[
{
"dollar":"15000",
"date":"1397-12-12"
}
]
how can remove array from json and show the json like this :
{
"dollar":"15000",
"date":"1397-12-12"
}
Easiest way (according his code):
change line
echo json_encode($out3);
to
echo json_encode($out3[0]);
One solution is that if you just want the latest value (in case there are multiple records in the table), then change the SELECT to order by date descending also set LIMIT to 1 to only get the 1 record anyway, and remove the loop to fetch the data and just fetch the 1 record...
$query3 = "SELECT `date`, `dollar`
FROM `tabl_dollar_date`
ORDER BY `date` desc
LIMIT 1";
$result3 = $connect->prepare($query3);
$result3->execute();
$row3 = $result3->fetch(PDO::FETCH_ASSOC);
echo json_encode($row3);
As you know which fields you want from the SELECT, it's good to just fetch those fields rather than always using *. This also means that as the result set only contains the fields your after, you can directly json_encode() the result set rather than extracting the fields from one array to another.
I am running a while loop in PHP selecting data from a mysql database. How can i find out what the last record is,
for example:
$sql="SELECT * from table1 ";
$rs=mysql_query($sql,$conn);
while($result=mysql_fetch_array($rs))
{
echo $result["col1"].' - '.$result["col2"].'<br>';
}
then when it gets to the last record i want to display it like:
echo 'Last Record: '.$result["col1"].' - '.$result["col2"].'<br>';
You basically need to record how many rows you have, and then set up a counter. You can do that using mysql_num_rows():
$sql="SELECT * from table1";
$rs = mysql_query($sql,$conn);
$numRows = mysql_num_rows($rs);
$i = 1;
while($result=mysql_fetch_array($rs))
{
echo ($i == $numRows) ? 'Last Record: '.$result["col1"].' - '.$result["col2"].'<br />' : $result["col1"].' - '.$result["col2"].'<br />';
$i++;
}
You should note though that the mysql_*() family of functions is now deprecated. For security and longevity, you really ought to be using MySQLi or PDO.
Get the total count of rows returned and check use a flag variable for the loop iterations and check in loop if flag == total rows
$t=mysql_num_row($rs);
$i=0;
while($result=mysql_fetch_array($rs))
{
$i++;
if($t == $i){
echo "Last Record ";
}
echo $result["col1"].' - '.$result["col2"].'<br>';
}
mysql_num_rows
You can simply use the sql query itself to get the last value, based on whatever ordering you want (or just use DESC to get the bottom of the natural order):
SELECT * FROM table1
ORDER BY your_column DESC
LIMIT 1;
Edit: Since you're looking for the last row, you could check with mysql_num_rows
$numrows = mysql_num_rows($rs);
$i = 1;
// in while loop...
if ($i === $numrows) {
// print last result
} else {
// print normal result
}
$i++;
// end while loop
Essentially, you want a counter for the record you are on and then write when the number of rows is the same as the row number you are on (e.g. the last one)
$sql="SELECT * from table1 ";
$rs=mysql_query($sql,$conn);
$num_rows = mysql_num_rows ($rs);
for ($i=0; $i < $num_rows; $i++) {
$result=mysql_fetch_array($rs);
if ($i == ($num_rows - 1)) {
echo 'Last Record: '.$result["col1"].' - '.$result["col2"].'<br>';
} else {
echo $result["col1"].' - '.$result["col2"].'<br>';
}
}
Future-proof this routine by doing it the "hard way":
while ($next_row = fetch_row(...)) {
if ($prev_row) { do_output($prev_row); }
$prev_row = $next_row;
}
if ($prev_row) { do_output($prev_row, FLAG_IS_LAST_ROW); }
Why? Future maintenance might make mysql_num_rows() unreliable, either because your result set gets too big, or because you want to interface with a variety of SQL backends.
By default, the MySQL client library pulls the entire result set into memory — that is how it knows the number of rows SELECTed without having to count fetches. This behavior is rather convenient for small result sets, but devastating for large result sets. This it is user-configurable. (The options are usually named something like "store_result v. use_result" or "buffered v. unbuffered.")
Additionally, most RDBMS interfaces do not make the size of the result set known in advance. If you want to interface with these some day in a reusable way, you'll need to change your approach.
I am creating a pagination script and I need to get the first and last results in the database query so that I can determine what results appear when the user clicks a page to go to. This is the code that I have at the minute:
// my database connection is opened
// this gets all of the entries in the database
$q = mysql_query("SELECT * FROM my_table ORDER BY id ASC");
$count = mysql_num_rows($q);
// this is how many results I want to display
$max = 2;
// this determines how many pages there will be
$pages = round($count/$max,0);
// this is where I think my script goes wrong
// I want to get the last result of the first page
// or the first result of the previous page
// so the query can start where the last query left off
// I've tried a few different things to get this script to work
// but I think that I need to get the first or last result of the previous page
// but I don't know how to.
$get = $_GET['p'];
$pn = $_GET['pn'];
$pq = mysql_query("SELECT * FROM my_table ORDER BY id ASC LIMIT $max OFFSET $get");
// my query results appear
if(!$pn) {
$pn = 1;
}
echo "</table><br />
Page $pn of $pages<br />";
for($p = 1;$p<=$pages;$p++) {
echo "<a href='javascript:void(0);' onclick='nextPage($max, $p);' title='Page $p'>Page $p</a> ";
}
I think you have few problems there, but I try to tackle them for you. First, as comments say above, you are using code that it vulnerable to SQL injection. Take care of that - you might want to use PDO, which is as easy use as MySQL extension, and will save you from many trouble (like injection).
But to your code, lets go through it:
You should ask DB to get count of the rows, not using mysql function, it's far more effective, so use SELECT count(*) FROM mytable.
For $pages use ceil() as you want all rows to be printed, if you have $max 5 and have 11 rows, round will make $pages 2, where you actually want 3 (last page just contains that last 11th row)
in LIMIT you want to LIMIT row_count OFFSET offset. You can calculate offset from page number, so: $max = row_count but $offset = ($max * $page) - $max. In your code if $get is directly the page, it means you get $get'th row (Not sure though what happens in your JS nextpage. Bare in mind that not all use JavaScript.)
I have prepared simple example here which uses PDO, maybe that gives you idea how simple it's use PDO.
The selecting rows shows example how to put parameters in SQL, it would be perfectly safe in this case state, 'SELECT * FROM pseudorows LIMIT '.$start.','.$max by I wanted to make an example how easy it is (and then safe):
// DB config
$DB_NAME = 'test';
$DB_USER = 'test';
$DB_PASSWD = 'test';
// make connection
try {
$DB_CONN = new PDO("mysql:host=localhost;dbname=".$DB_NAME, $DB_USER, $DB_PASSWD);
$DB_CONN->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch (PDOException $e) {
die($e);
}
// lets say user param 'p' is page, we cast it int, just to be safe
$page = (int) (isset($_GET['p'])?$_GET['p']:1);
// max rows in page
$max = 20;
// first select count of all rows in the table
$stmt = $DB_CONN->prepare('SELECT count(*) FROM pseudorows');
$stmt->execute();
if($value = $stmt->fetch()) {
// now we know how many pages we must print in pagination
// it's $value/$max = pages
$pages = ceil($value[0]/$max);
// now let's print this page results, we are on $page page
// we start from position max_rows_in_page * page_we_are_in - max_rows_in_page
// (as first page is 1 not 0, and rows in DB start from 0 when LIMITing)
$start = ($page * $max) - $max;
$stmt = $DB_CONN->prepare('SELECT * FROM pseudorows LIMIT :start,:max');
$stmt->bindParam(':start',$start,PDO::PARAM_INT);
$stmt->bindParam(':max', $max,PDO::PARAM_INT);
$stmt->execute();
// simply just print rows
echo '<table>';
while($row = $stmt->fetch()) {
echo '<tr><td>#'.$row['id'].'</td><td>'.$row['title'].'</td></tr>';
}
echo '</table>';
// let's show pagination
for($i=1;$i<=$pages;$i++) {
echo '[ '.$i.' ]';
}
}
mysql_fetch_array returns an associative array
Which means you can use reset and end to get the first and last results:
$pqa = mysql_fetch_array($pq);
$first = reset($pqa);
$last = end($pqa);
I don't see how you plan to use the actual results, just page numbers should be sufficient for pagination.
Still, hope it helps. And yes, upgrade to mysqli, so your code doesn't get obsolete.
I am trying to create a class registration system for a client that utilizes PHP and MySQL. I have the database and table all set up and that part works just fine, however, the client has requested that upon registration, if there are 3 or fewer students enrolled to warn that the class may not run.
I'm trying to use the count() function as well as passing a dynamic variable from a cookie, set from the registration PHP script. However, I've hit a roadblock. I can't seem to get the count() function to actually count the rows. My select statement is below. Any help would be greatly appreciated.
$class = $_COOKIE["class"];
$min_check = "SELECT class_list, COUNT(class_list) as count
FROM T_Student WHERE class_list = '$class'
GROUP BY class_list
HAVING count < 20";
$result = mysql_query($min_check);
$count = mysql_num_rows($result);
if ($count < 4)
{
echo "IF THERE ARE 3 OR FEWER PEOPLE SIGNED UP FOR THIS CLASS, IT MAY NOT RUN.\n";
echo "THERE ARE CURRENTLY " . $count . " PEOPLE SIGNED UP.\n";
}
else if ($count > 4)
{
echo "There are currently " . $count . " people signed up for this class.";
}
?>
Your SQL query is returning a list of the class_list values, along with a count of each specific instance, where there are less than 20 people registered.
$count = mysql_num_rows($result);
...is getting the number of records returned in the resultset, not the alias count value, which is why you aren't seeing the output you expect. You need to read into your resultset to get the value:
while ($row = mysql_fetch_assoc($result)) {
$count = $row['count'];
if($count < 4) { ... }
}
The count that you want is returned in the row of the query. the mysql_num_rows will count the rows returned, which is not what you want. Use this instead.
$result = mysql_query($min_check);
$count = mysql_fetch_row($result);
$count = $count[0];
On a first glance, the HAVING count < 20 is unnecessary.
You use the MySQL-count-function, but never retrieve it's value!? Use:
$firstRow = mysql_fetch_row($result);
$count = $firstRow[1]; // 1 indicates the second column (0 being the first)
I don't recommend using known MySQL identifiers like count. It's confusing.
$class = mysql_real_escape_string($_COOKIE["class"]);
$min_check = "SELECT class_list, COUNT(class_list) as mycount
FROM T_Student WHERE class_list = '$class'
GROUP BY class_list
HAVING mycount < 20";
Don't forget to escape the contents of that cookie!
The error is that count is a reserved word. You need to either surround it in backticks `count` or even better, use a different moniker. It's not an error per se, but it's just too confusing.
Next up, you are not actually retrieving the mycount result from the database. I suggest using code something like this:
$result = mysql_query($min_check);
while( $row = mysql_fetch_assoc($result) ) {
$people_count = $row['mycount'];
if ($people_count < 4) { echo "this" }
else { echo "that" }
}
well, i wanna pull out some data from a mysql view, but the wuery dos not seem to retrieve anything ( even though the view has data in it).
here is the code i've been "playing" with ( i'm using adodb for php)
$get_teachers=$db->Execute("select * from lecturer ");
//$array=array();
//fill array with teacher for each lesson
for($j=0;$j<$get_teachers->fetchrow();++$j){
/*$row2 = $get_lessons->fetchrow();
$row3=$row2[0];
$teach=array(array());
//array_push($teach, $row3);
$teach[$j]=mysql_fetch_array( $get_teachers, TYPE );
//echo $row3;*/
$row = $get_teachers->fetchrow();
//$name=$row[0]+" "+$row[0]+"/n";
//array_push($teach, $row1);
echo $row[0]; echo " ";echo $row[1]." ";
//$db->debug = true;
}
if i try something like "select name,surname from users", the query partially works . By partially i mean , while there are 2 users in the database, the loop only prints the last user.
the original query i wanted to execute was this
$get_teachers=$db->Execute("select surname,name from users,assigned_to,lessons
where users.UID=assigned_to.UID and lessons.LID=assigned_to.LID and
lessons.term='".$_GET['term']."'");
but because it didnt seem to do anything i tried with a view ( when you execute this in the phpmyadmin it works fine(by replacing the GET part with a number from 1 to 7 )
the tables in case you wonder are: users,assigned_to and lessons. ( assigned_to is a table connecting each user to a lesson he teaches by containing UID=userid and LID=lessonid ). What i wanted to do here is get the name+surname of the users who teach a lesson. Imagine a list tha displays each lesson+who teaches it based on the term that lesson is available.
Looking at http://adodb.sourceforge.net/ I can see an example on the first page on how to use the library:
$rs = $DB->Execute("select * from table where key=123");
while ($array = $rs->FetchRow()) {
print_r($array);
}
So, you should use:
while ($row = $get_teachers->fetchrow()) {
instead of:
for ($j = 0; $j < $get_teachers->fetchrow(); ++$j) {
The idea with FetchRow() is that it returns the next row in the sequence. It does not return the number of the last row, so you shouldn't use it as a condition in a for loop. You should call it every time you need the next row in the sequence, and, when there are no more rows, it will return false.
Also, take a look at the documentation for FetchRow().
for($j=0;$j<$get_teachers->fetchrow();++$j){
... a few lines later ...
$row = $get_teachers->fetchrow();
See how you call fetchrow() twice before actually printing anything? You remove two rows from the result set for every 1 you actually use.
while ($row = $get_teachers->fetchrow()) {
instead and don't call fetchrow() again within the loop.
Because you're fetching twice first in the loop
for($j=0;$j<$get_teachers->fetchrow();++$j){
... some code ...
// And here you fetch again
$row = $get_teachers->fetchrow();
You should use it like this
while ($row = $get_teachers->fetchrow()) {