wp get_results - 过滤唯一记录

Question

我的数据库中有类别列，我必须使用 $wpdb->get_results 列出唯一类别，如何过滤它？见下面的代码...

<?php
global $wpdb;
$table_name = $wpdb->prefix . 'servicer';
$results = $wpdb->get_results("SELECT * FROM " . $table_name . " WHERE is_deleted = 0", ARRAY_A);
?>
<ul class="list-unstyled">
<?php

foreach($results as $key => $rec)
{
    echo "<li>" . $rec['category'] . "</li>";
}

?>
</ul>

目前的结果......

cat1
cat1
cat1
cat2
cat3
cat4
cat4

预期结果...... cat1 cat2 cat3 cat4

Answer 1

使用GROUP BY

$results  = $wpdb->get_results("SELECT * FROM ".$table_name." WHERE 
is_deleted = 0 GROUP BY category", ARRAY_A); 

或 使用DISTINCT

$results  = $wpdb->get_results("SELECT DISTINCT(category),* FROM 
".$table_name." WHERE is_deleted = 0", ARRAY_A);