Select from DB where VALUES NOT EQUALS = array

Question

im doing something where users has a local database and when he clicks to checks new books, it get all the IDS(fixed) form his local database and create String separeted by comma (1,2,3,4,5) and then do a GET to my server

www.myserver.com/getNews?ids=1,2,4,10

and in the server side i do this:

1) Get the last ID(fixed) and set in a var called $total 2) get the IDS send by the user and create a array using .explode(",") 3) get the missing values $missing = array_diff(range(1,$total),$ids); get max id and get the missing numbers between the $total and $ids

and here come the part that i think its heavy:

for each $missing value i do a select and build a array to display as json

    foreach($missing as $m) {

         $sql = "SELECT * FROM `books` WHERE id='$m'";
while($row =mysqli_fetch_assoc($result))
    {


$emparray[] = array_map('utf8_encode', $row);
    }
}
    echo json_encode($emparray);

this is the only one approach or is there any other more light function?

This is commonly known as [n + 1 query problem](http://stackoverflow.com/questions/97197/what-is-the-n1-selects-issue). — Marco Aurélio Deleu, Nov 12 '15 at 13:33

score 4 · Accepted Answer · answered Nov 12 '15 at 13:17

4

you can try this way. Implode your array with comma then use NOT IN condition in your query to select all books you want.

$strMissing = implode(',', $missing);

$sql = "SELECT * FROM `books` WHERE id NOT IN (".$strMissing.")";

answered Nov 12 '15 at 13:17

ThinkTank

1,187
9
15

jesus thats just perfect!! You know the tool very nice, reduced 60lines to just almost 10. Worked perfectly! the only thing i had to change was the $missing to the $ids (var of ids that the user already has in his Database), $missing can be removed from my code thank you – user2582318 Nov 12 '15 at 13:45

Select from DB where VALUES NOT EQUALS = array

1 Answers1