I want to go through a list of numbers and find the first number missing when the list is sorted numerically.

For example, consider this resultant set of numbers from a query:

```
A
---
0
1
3
4
5

```

I need a query to go through this list in numerical order from lowest to highest and return the first number missing from the list of numbers that would otherwise be complete and numerically sorted. So in the above example, the query should return ***2***. Below are some more examples. Requirements: must start checking at value 0, must return the first value missing from the NUMERICALLY SORTED list, must only return 1 number.

```
A
---
1
3
4
5

/* return 0 */

A
---
0
1
2
3
4
5
8
9

/* return 6*/

```