WordPress建站wpdb操作数据库增删改查的基础用法

global $wpdb;

// 查询条件
$page_author_id = 1;
$post_type_name = 'page';

// 使用 $wpdb->prepare()
$pages = $wpdb->get_results( $wpdb->prepare( 
    "
    SELECT post_title, post_content 
    FROM $wpdb->posts
    WHERE post_author = '%d' 
    AND post_type = '%s'
    ",
    $page_author_id, // %d because it is number
    $post_type_name // %s because it is string
) );

// 输出结果
if( $pages ) {
    foreach ( $pages as $page ) {
        echo $page->post_title;
    }
}

global $wpdb;
$table = $wpdb->prefix.'you_table_name';
$data = array('column1' => 'data one', 'column2' => 123);
$format = array('%s','%d');
$wpdb->insert($table,$data,$format);
$my_id = $wpdb->insert_id;

$data = [ 'a' => NULL ]; // NULL value.
$format = [ NULL ];  // Ignored when corresponding data is NULL, set to NULL for readability.
$where = [ 'id' => NULL ]; // NULL value in WHERE clause.
$where_format = [ NULL ];  // Ignored when corresponding WHERE data is NULL, set to NULL for readability.
$wpdb->update( $wpdb->prefix . 'my_table', $data, $where, $format, $where_format );
$wpdb->update( $wpdb->prefix . 'my_table', $data, $where ); // Also works in this case.

<?php $wpdb->query('query'); ?> 

$wpdb->query("DELETE FROM $wpdb->postmeta WHERE post_id = '13' AND meta_key = 'gargle'");

$wpdb->query("UPDATE $wpdb->posts SET post_parent = 7 WHERE ID = 15 AND post_status = 'static'");

<?php $wpdb->get_var('query',column_offset,row_offset); ?> 

<?php
$user_count = $wpdb->get_var($wpdb->prepare("SELECT COUNT(*) FROM $wpdb->users;"));
echo '<p>User count is ' . $user_count . '</p>';
?>

<?php
$meta_key = 'miles';//set this to appropriate custom field meta key
$allmiles=$wpdb->get_var($wpdb->prepare("SELECT sum(meta_value) FROM $wpdb->postmeta WHERE meta_key = %s", $meta_key));
echo '<p>Total miles is '.$allmiles . '</p>';
?>

<?php $wpdb->get_row('query', output_type, row_offset); ?> 

$mylink = $wpdb->get_row("SELECT * FROM $wpdb->links WHERE link_id = 10");  

echo $mylink->link_id; // prints "10"  

$mylink = $wpdb->get_row("SELECT * FROM $wpdb->links WHERE link_id = 10", ARRAY_A);  

echo $mylink['link_id']; // prints "10"  

$mylink = $wpdb->get_row("SELECT * FROM $wpdb->links WHERE link_id = 10", ARRAY_N);  

echo $mylink[1]; // prints "10"  

<?php $wpdb->get_col('query',column_offset); ?>