MySQL 检查 null 如果值为空，则使用 php

Question

I have multiple arrays similar to below.

{
  ["sku_original"]=>
  string(33) "98iuoo"
  ["po"]=>
  string(5) "9897"
  ["ca"]=>
  string(3) "557"
  ["cl"]=>
  string(5) "33"
  ["aa"]=>
  string(3) "80"
  ["ad"]=>
  NULL
  ["da"]=>
  string(4) "143.9"
  ["dr"]=>
  NULL
  ["cors"]=>
  NULL
}

I want to use IS NULL condition when a value is null in the array else I have to check equal to condition if not empty. I have tried something like below.

$po =  $option['po'] != NULL ? $option['po'] : NULL ;
$ca =  $option['ca'] != NULL ? $option['ca'] : NULL ;
$cl =  $option['cl'] != NULL ? $option['cl'] : NULL ;
$aa = $option['aa'] != NULL ? $option['aa'] : NULL ;
$ad = $option['ad'] != NULL ? $option['ad'] : NULL ;
$da = $option['da'] != NULL ? $option['da'] : NULL ;
$dr = $option['dr'] != NULL ? $option['dr'] : NULL ;
$cors = $option['cors'] != NULL ? $option['cors'] : NULL ;

The above code is not assigning value to a variable if option index is null I also tried is_null.

and SQL like below.

$sql = "SELECT abc FROM `abc` WHERE `po` = $po AND `ca` = $ca AND `cl` = $cl AND `aa` = $aa AND `ad` = $ad AND `da` = $da AND `dr` = $dr AND `dr` = '$dr' AND `cors` = '$cors' `sku` = '$sku' ";

I have to check IS NULL in SQL when value is null else I have to use equal to

Answer 1

As you iterate your options variable (assuming you have already validated all of the keys using a whitelist of table column names), conditionally write a static IS NULL expression into the WHERE clause or a bound parameter with a non-null value.

// unconditionally include sku
$where[] = "sku = ?";
$params = ['s', $sku];
foreach ($option as $key => $value) {
    if ($value === null) {
        $where[] = "$key IS NULL";
    } else {
        $where[] = "$key = ?";
        $params[0] .= 's';
        $params[] = $value;
    }
}

$sql = "SELECT column_with_different_name_from_table
        FROM abc
        WHERE " . implode(" AND " , $where);
$stmt = $conn->prepare($sql);
$stmt->bind_param(...$params);
$stmt->execute();
$result = $stmt->get_result();

foreach ($result as $row) {
    echo $row['column_with_different_name_from_table'] . "<br>";
}

Answer 2

You can use NULL in prepared statements directly. Heres a dynamic way to build your query

// put all your variables in an array
$vars = array('po', 'ca', 'ab') ;

// iterate through and set up your key/value pairs
foreach ($vars as $var) {
  $val = (isset($option[$var]) && !is_null($option[$var])) ? $option[$var] : NULL;
  $q[] = " $var = ? ";
  $v[] = $val ;     
}

// set up the prepared statement
$query = "SELECT abc FROM `abc` WHERE " . implode(" AND " , $q) ;
$stmt = $mysqli->prepare($query);
$types = str_repeat("s", count($q)) ;
$stmt->bind_param($types, ...$v);
$stmt->execute();

Answer 3

If you merely want optinal criteria, you can handle this in SQL by asking "is the parameter set, then use it, else don't".

$sql = "SELECT abc FROM abc WHERE (po = $po OR $po IS NULL) AND (ca = $ca OR $ca IS NULL) ...";

which can also be written as

$sql = "SELECT abc FROM abc WHERE po <=> COALESCE($po, po) AND ca <=> COALESCE($ca, ca) ...";

in MySQL (thus having each parameter only once in the query instead of having to use them twice).

UPDATE: I have focused on the SQL in above answer. It has been mentioned that you should not build the query string by concatenation, but use prepared statements and bind the variables. This is correct. I am not a PHP programmer, but it seems the difference in above assignments is mainly to replace the $ with a : . Something like this:

$sql = "SELECT abc FROM abc WHERE po <=> COALESCE(:po, po) AND ca <=> COALESCE(:ca, ca) ...";
$query = $pdo->prepare($sql);
$query->bindParam(":po", $option["po"]);
$query->bindParam(":ca", $option["ca"]);
...
$query->execute();