- previous occurrence of string "2" (if a previous entry is present)
```
select progressive_no
from MyTable
where ColumnX == :string
and progressive_no < :lastno
order by progressive_no desc
limit 1;
```
- next occurrence of string "2" (if another entry is present)
```
select progressive_no
from MyTable
where ColumnX == :string
and progressive_no > :lastno
order by progressive_no
limit 1;
```
- first occurrence of string "2"
```
select progressive_no
from MyTable
where ColumnX == :string
order by progressive_no
limit 1;
```
- last occurrence of string "2"
```
select progressive_no
from MyTable
where ColumnX == :string
order by progressive_no desc
limit 1;
```
Where :string is the string value you are looking for ('2' in your example) and :lastno is the progressive_no where you are looking from (5 in your example).
You will want a unique index on (ColumnX, progressive_no).