Find which numbers in [1, 161] are not in the result set?
To find gaps in a number range:

Test table and data:

mysql&gt; CREATE TABLE wp_blogs
    -&gt; (
    -&gt;   blog_id INTEGER
    -&gt; );

mysql&gt; insert into wp_blogs values(1);
mysql&gt; insert into wp_blogs values(2);
mysql&gt; insert into wp_blogs values(4);
mysql&gt; insert into wp_blogs values(6);
mysql&gt; insert into wp_blogs values(7);
mysql&gt; insert into wp_blogs values(8);
mysql&gt; insert into wp_blogs values(10);


Query:

mysql&gt; SELECT a.blog_id+1 AS start, MIN(b.blog_id) - 1 AS end
    -&gt;     FROM wp_blogs AS a, wp_blogs AS b
    -&gt;     WHERE a.blog_id &lt; b.blog_id
    -&gt;     GROUP BY a.blog_id
    -&gt;     HAVING start &lt; MIN(b.blog_id);
+-------+------+
| start | end  |
+-------+------+
|     3 |    3 |
|     5 |    5 |
|     9 |    9 |
+-------+------+