php - Correct mysql query to query one table and have that provide information for another table query -

i have 2 separate tables, both of need query simultaneously correct information display. tables members , posts. through html form, user enters criteria members table, , need use primary index of specific members find posts submitted members , sort on posts table results. results mixture of rows 2 tables. both tables have primary index of name 'id'. far i've come is:

$sql_get_posts = mysqli_query($link, "(select id, username members active='y' , gender='m' , city='yuma' , state='arizona') union (select * posts member_id='id' , active='y' order list_weight desc)") or die(mysqli_error($link)); 

the error i'm getting "the used select statements have different number of columns".

i need cycle through returned results both tables populate content seen user:

<?php    while ($row = mysqli_fetch_array($sql_get_posts)) {      $post_id = $row['id']; //this should post primary index named 'id', not member primary index name 'id'      $member_id = $row['member_id']; //this member_id row in post table referencing particular member wrote post       $member_username = $row['username']; //this row stored in member table      $title = $row['title']; //this row stored in post table      ******//and on , on getting rows post table    } 

edit sql tables:

create table if not exists `members` (  `id` int(11) not null auto_increment,  `username` varchar(20) not null,  `age` varchar(3) not null,  `gender` varchar(1) not null,  `city` varchar(20) not null,  `state` varchar(50) not null,  `active` enum('y','n') not null default 'y',  `created_date` timestamp not null default current_timestamp on update current_timestamp,   primary key (`id`) ) engine=myisam  default charset=latin1 auto_increment=3 ;   create table if not exists `posts` (   `id` int(11) not null auto_increment,   `member_id` int(11) not null,   `title` text not null,   `comments` enum('y','n') not null default 'y',   `post_date` timestamp not null default current_timestamp on update current_timestamp,   `list_weight` double not null,   `active` enum('y','n') not null default 'y',   primary key (`id`) ) engine=myisam  default charset=latin1 auto_increment=47 ; 

use join instead of union, union assumes tables you're combining similar, whereas join merges columns of 2 tables.

something like:

select members.id, members.username, posts.* members inner join posts on members.id = posts.member_id members.active='y' , members.gender='m' , members.city='yuma' , members.state='arizona' order posts.list_weight desc