How to search multiple values in SQLite? - php

Question

I'm creating a very simple PHP file that searches a table in my SQLite database.
I want it to filter my table according to 2 parameters, min and max, but I want to be able to specify one parameter, both or even none. How do I translate that into a SQL query?
<?php
$db = new PDO('sqlite:database.db');
$min = $_GET['min'];
$max = $_GET['max'];
if($min == '') $min = -1;
if($max == '') $max = -1;
$res = $db->prepare('SELECT * FROM Roteiro WHERE ...');
$res->execute(array(...));
$test = $res->fetchAll();
print_r($test);
?>

Answer 1

where (? > a or ? is null)
and (? = foo or ? is null)
-- etc...
The trick is let the condition be satisfied if the value is null. Make sure you pass type null, not some empty string or other falsy value.
The query optimizer should optimize these extra conditions away no problem because its easy for it to see they never vary per row.
an equivalent way to say it
where (? is not null and ? > a)
and (? is not null and ? = foo)
but I prefer the first way.

Answer 2

Youll need to build the statement dynamically:
$db = new PDO('sqlite:database.db');
$min = isset($_GET['min']) && !empty($_GET['min']) ? (integer) $_GET['min'] : null;
$max = isset($_GET['max']) && !empty($_GET['max']) ? (integer) $_GET['max'] : null;
$base = 'SELECT * FROM Roteiro';
$params = array();
if(null != $min && null != $max) {
// im using BETWEEN here just for simplicity int he example,
// but you could (should?) use separate statements with
// typical <,> comparison ops.
$base .= ' WHERE the_column BETWEEN :min AND :max';
$params[':min'] = $min;
$params[':max'] = $max;
} elseif(null !== $max) {
$base .= ' WHERE the_column < :max';
$params[':max'] = $max;
} elseif(null != $min) {
$base .= ' WHERE the_column > :min';
$params[':min'] = $min;
}
$db->prepare($base);
$db->execute($params);

Answer 3

You'll want to dynamically create the query from the information you have.
So, lets say you want to filter some table by a optional minimal and an optional maximal value.
SELECT some_row
FROM some_table
WHERE filter_row < [max]
AND filter_row > [min]
An easy way to do this would be to simply store the part of your SQL-query that filters by maximum and minimum and append it to the query when needed/defined:
$sql = "SELECT some_row
FROM some_table ";
if (isset($max) && isset($min)){
$sql .= "WHERE filter_row < ?
AND filter_row > ?";
} else if (isset($max) ){
$sql .= "WHERE filter_row < ?";
} else if (isset($min) ){
$sql .= "WHERE filter_row > ?";
}
if ($stmt = $mysqli->prepare($sql)) {
// bind parameters according to the given/available
// parameters and execute
}
I'm not sure if the query will work since I have nothing to test it here, but the idea should be clear.
This is just a very simple solution which will get very large and ugly with a growing list of optional parameters. So, if you need it more often and with more parameters, consider using a "Query Builder".