How to use variables in WHERE clause for a SQL SELECT query

问题

My SQL SELECT query has 3 variables set by a HTML form, however these variables can be null:

   $suburb = (isset($_POST['suburb'])) ? $_POST['suburb'] : '';
   $postcode = (isset($_POST['postcode'])) ? $_POST['postcode'] : '';
   $state = (isset($_POST['state'])) ? $_POST['state'] : '';

When all 3 variables are entered in the form the SELECT query processes fine (due to the AND's in the WHERE clause). But when one or more variables are blank, the SELECT query errors as it is looking for a NULL value in the databse.

What I want it to do is when a variable is null, I don't want a where clause for it

Query:

$sql = <<<SQL
SELECT 
    cs.customerRefId,
    cc.firstName,
    cc.lastName,
    cc.email,
    cc.phone,
    cc.mobile,
    cs.seekingAddressSuburb, 
    cs.seekingAddressPostcode, 
    cs.seekingAddressState
FROM 
    customer_seeking cs
LEFT JOIN
    customer_contact cc ON cc.customerRefId = cs.customerRefId
WHERE
cs.seekingAddressSuburb = '$suburb' AND
cs.seekingAddressPostcode = '$postcode' AND
cs.seekingAddressState = '$state'
SQL;  


if(!$result = $db->query($sql)){
    die('There was an error running the query [' . $db->error . ']');
}

For example if only the state variable is defined (cs.seekingAddressSuburb = '$suburb' AND cs.seekingAddressPostcode = '$postcode' AND are removed from the WHERE clause):

$sql = <<<SQL
SELECT 
    cs.customerRefId,
    cc.firstName,
    cc.lastName,
    cc.email,
    cc.phone,
    cc.mobile,
    cs.seekingAddressSuburb, 
    cs.seekingAddressPostcode, 
    cs.seekingAddressState
FROM 
    customer_seeking cs
LEFT JOIN
    customer_contact cc ON cc.customerRefId = cs.customerRefId
WHERE
cs.seekingAddressState = '$state'
SQL;

回答1:

construct your query in a String then add one by one if each field have value. example :

$query = "select * from table1 where 1=1";
if(!empty($suburb)) $query.=" and cs.seekingAddressSuburb = '$suburb'";
if(!empty($postcode)) $query.=" and cs.seekingAddressPostcode = '$postcode'";
if(!empty($state)) $query.=" and cs.seekingAddressState = '$state'";
//run your query then

回答2:

Im not sure if this is what you want to do but you try this code in PHP FIDDLE

$a = 'a';
$b = 'b';
$c;

$SQL = "SELECT * FROM TABLE WHERE A = $a". (!empty($b) ? ' AND b ='. $b: '')  ." ". (!empty($c) ? 'AND C ='. $c: '');

echo $SQL;

TO RELATE IN YOUR CODE

$suburb = if(isset($_POST['suburb']));
$postcode = if(isset($_POST['postcode']));
$state = if(isset($_POST['state']));

$SQL = "SELECT cs.customerRefId,
cc.firstName,
cc.lastName,
cc.email,
cc.phone,
cc.mobile,
cs.seekingAddressSuburb, 
cs.seekingAddressPostcode, 
cs.seekingAddressState
FROM 
    customer_seeking cs
LEFT JOIN
    customer_contact cc ON cc.customerRefId = cs.customerRefId WHERE cs.seekingAddressSuburb = $suburb". (!empty($postcode) ? ' AND cs.seekingAddressPostcode ='. $postcode: '')  ." ". (!empty($state) ? 'AND cs.seekingAddressState ='. $state: '');

echo $SQL;

来源：https://stackoverflow.com/questions/17015766/how-to-use-variables-in-where-clause-for-a-sql-select-query

标签

php

mysql

forms

where-clause