返回值取决于从SQL查询返回的行数

Question

I'm new to PHP and SQL and I'm trying to write a function that will return true if an SQL query returns at least one result.

What I have so far is

function isNew($canNum)
  {
  connectToDatabase();

   SELECT COUNT(*) as cnt FROM
   FROM 'cans' c
   WHERE c.date >= DATE_SUB(NOW(), INTERVAL 1 DAY)
   AND c.canId = '$canNum';

  disconnectDatabase();
  //return true if above returns a row

  disconnectDatabase();
  }

My question would be how to do the return since the count is not a php variable that I can do a < comparison with.

Answer 1

function isNew($canNum)
  {
if (count(mysql_fetch_assoc(mysql_query("
   SELECT COUNT(*) as cnt FROM
   FROM 'cans' c
   WHERE c.date >= DATE_SUB(NOW(), INTERVAL 1 DAY)
   AND c.canId = '$canNum';
")))>0)
{
return true;
}
else
{
return false;
}
  }

Answer 2

May be you need to use one of these php functions in your code

<?php

$q = mysql_query("your query here!")

if($q = mysql_num_row() > 1 ){
//your code
}

?>

Answer 3

<?php
    function isNew($canNum)
    {
    $con=mysqli_connect("localhost","UID","PSW","DB"); //Db connection
    //connectToDatabase();

    $sql="SELECT COUNT(*) as cnt FROM 'cans' c WHERE c.date >= DATE_SUB(NOW(), INTERVAL 1 DAY) AND c.canId = '$canNum'";
    $result = mysqli_query($con,$sql);
    $count_1=mysqli_fetch_array($result);
    $count=$count_1['cnt'];
    // disconnectDatabase();
    //return true if above returns a row
    mysqli_close($con);
    //  disconnectDatabase();
    return $count; //returns count you can modify it the way you want
}

    echo "Current count is ".isNew(10);
?>

Answer 4

Your code doesn't look like a piece of PHP code! Try this:

$link = mysql_connect('localhost', 'mysql_user', 'mysql_password');
if (!$link) {
    die('Not connected : ' . mysql_error());
}

// make foo the current db
$db_selected = mysql_select_db('foo', $link);
if (!$db_selected) {
    die ('Can\'t use foo : ' . mysql_error());
}

$number=mysql_num_rows(mysql_query("SELECT `canId` FROM `cans` WHERE `date` >= DATE_SUB(NOW(), INTERVAL 1 DAY) AND `canId` = '$canNum';"));

if($number>0){
  // do what you want to do
}

mysql_close($con);

Answer 5

Please avoid using mysql_query as suggested in the other answers and look into mysqli_query or PDO . With PDO, you can do something like:

function isNew($canNum){
  $db = new PDO();
  $statement = $db->prepare('....your query... WHERE canID=:canID');
  $statement->bindParam(':canID', $canNum);
  $statement->execute();
  if($result = $statement->fetch()){
     //exists
     return true;
  } else {
     return false;
  }
}

You'll also avoid SQL injections as well;