Query with Foreach inside - mysql

Question

I would like Wordpress query to have a foreach in it.
$aid=0;
foreach ($QA as $key => $value) {
AND wp_postmeta.post_id IN (
SELECT wp_postmeta.post_id
FROM wp_postmeta, wp_posts
WHERE wp_posts.ID = wp_postmeta.post_id
AND wp_posts.post_status = 'publish'
AND wp_posts.post_type = 'post'
AND wp_postmeta.meta_key = '$key'
AND wp_postmeta.meta_value = '$value'
)
$aid++;
}
But it's not working that way, so I'm asking for help -
How I can put foreach in sql query?
Full example of code below.
<?php
function query_products($QA) {
global $wpdb;
global $post;
global $pageposts;
$querystr = "
SELECT wp_posts.*, wp_postmeta.*
FROM wp_postmeta, wp_posts
WHERE wp_posts.ID = wp_postmeta.post_id
AND wp_posts.post_status = 'publish'
AND wp_posts.post_type = 'post'
AND wp_postmeta.meta_key = 'country'
AND wp_postmeta.meta_value = 'Denmark'
$aid=0;
foreach ($QA as $key => $value) {
AND wp_postmeta.post_id IN (
SELECT wp_postmeta.post_id
FROM wp_postmeta, wp_posts
WHERE wp_posts.ID = wp_postmeta.post_id
AND wp_posts.post_status = 'publish'
AND wp_posts.post_type = 'post'
AND wp_postmeta.meta_key = '$key'
AND wp_postmeta.meta_value = '$value'
)
$aid++;
}
ORDER BY wp_postmeta.meta_value ASC
";
$pageposts = $wpdb->get_results($querystr, OBJECT);
}
$QA = array (
'key1' => 'value1',
'key2' => 'value2',
'key3' => 'value3',
);
query_products($QA);
?>

Answer 1

$querystr = "
SELECT wp_posts.*, wp_postmeta.*
FROM wp_postmeta, wp_posts
WHERE wp_posts.ID = wp_postmeta.post_id
AND wp_posts.post_status = 'publish'
AND wp_posts.post_type = 'post'
AND wp_postmeta.meta_key = 'country'
AND wp_postmeta.meta_value = 'Denmark'
";
$aid=0;
foreach ($QA as $key => $value) {
$querystr .= "
AND wp_postmeta.post_id IN (
SELECT wp_postmeta.post_id
FROM wp_postmeta, wp_posts
WHERE wp_posts.ID = wp_postmeta.post_id
AND wp_posts.post_status = 'publish'
AND wp_posts.post_type = 'post'
AND wp_postmeta.meta_key = '$key'
AND wp_postmeta.meta_value = '$value'";
)
$aid++;
}
$querystr .=" ORDER BY wp_postmeta.meta_value ASC";

Answer 2

Without knowing what the query is supposed to accomplish, I can only suggest something like this:
<?php
$querystr = "
SELECT wp_posts.*, wp_postmeta.*
FROM wp_postmeta, wp_posts
WHERE wp_posts.ID = wp_postmeta.post_id
AND wp_posts.post_status = 'publish'
AND wp_posts.post_type = 'post'
AND wp_postmeta.meta_key = 'country'
AND wp_postmeta.meta_value = 'Denmark'
AND wp_postmeta.post_id IN (
SELECT wp_postmeta.post_id
FROM wp_postmeta, wp_posts
WHERE wp_posts.ID = wp_postmeta.post_id
AND wp_posts.post_status = 'publish'
AND wp_posts.post_type = 'post'
";
if (count($QA) >= 1) {
$querystr .= " AND ( ";
foreach($QA as $key => $value) {
$querystr .= "(wp_postmeta.meta_key = '{$key}' AND wp_postmeta.meta_value = '{$value}') OR ";
}
// get rid of the last "OR" in the string
$querystr = substr($querystr,0,strrpos($querystr,"OR"));
$querystr .= " ) ";
}
$querystr .= " ORDER BY wp_postmeta.meta_value ASC ";
?>
Note I used "OR" above because you'll never get any results when checking a single field for multiple values using an "AND" clause.

Answer 3

You need to pass all the keys in as an array or issue the full query iteratively (including the select). I would not recommend the latter, because performance will be poor (excessive database round trips are bad). So, I'd do something like this as long as $QA is not too huge. I believe it to be a little bit simpler than the full subquery originally submitted by using an EXISTS clause, but this may be more a matter of taste than one truly being better than the other.
<?php
function query_products($QA) {
global $wpdb;
global $post;
global $pageposts;
$querystr = "
SELECT wp_posts.*, wp_postmeta_a.*
FROM wp_postmeta AS wp_postmeta_a, wp_posts, wp_postmeta AS wp_postmeta_b
WHERE wp_posts.ID = wp_postmeta_a.post_id
AND wp_posts.post_status = 'publish'
AND wp_posts.post_type = 'post'
AND wp_postmeta_a.meta_key = 'country'
AND wp_postmeta_a.meta_value = 'Denmark'
";
$aid=0;
foreach ($QA as $key => $value) {
$querystr .= "
AND EXISTS (SELECT 1
FROM wp_postmeta AS wp_postmeta_b
WHERE wp_posts.ID = wp_postmeta_b.post_id
AND wp_postmeta_b.meta_key = '$key'
AND wp_postmeta_b.meta_value = '$value')
";
$aid++;
}
$querystr .= " ORDER BY wp_postmeta_a.meta_value ASC ";
$pageposts = $wpdb->get_results($querystr, OBJECT);
}
$QA = array (
'key1' => 'value1',
'key2' => 'value2',
'key3' => 'value3',
);
query_products($QA);
?>