php - Count the number of rows in MySQL table with criteria depending on other table -

i've got 2 tables:

content: id    access 1     3 2     5 3     9  viewlevels: id   group 1    [10,12,15] 2    [8,12,11] 3    [9,10,5] 

the access field in content related id field in viewlevels.

i select rows in viewlevels depending on current user group. example, if group = 10, query select rows 1 , 3. if group 12, select rows 1 , 2, etc. i'm using following query:

$query="select id #__viewlevels rules '%$group%'"; 

my challenge count number of rows column id in table content access matches selected id's above query on table viewlevels.

i tried following code returning error: undefined variable: nartigos

$query="select count(id) #__content access in (select id #__viewlevels rules '%$group%')";  if ($stmt = mysqli_prepare($link, $query)) {      /* execute query */     mysqli_stmt_execute($stmt);      /* store result */     mysqli_stmt_store_result($stmt);      $nartigos=mysqli_stmt_num_rows($stmt);      /* close statement */     mysqli_stmt_close($stmt); };  echo "nº de artigos " .$nartigos; 

first of all, should normalize data. consider having many-to-many join table viewlevels instead of having groups in 1 row. might this:

access_id  group_id 1          10 1          12 1          15 2          8 2          11 2          12 3          5 3          9 3          10 

that make query simple as

select c.id `content_id`, count(v.access_id) `content_count` content c inner join viewlevels v   on c.access_id = v.access_id v.group_id = ? group c.id 

here ? group id querying against.

without normalization (which again recommend do), still use join, this:

select c.id `content_id`, count(v.access_id) `content_count` content c inner join viewlevels v   on c.access_id = v.access_id v.group '%?%' group c.id