sqlite3 row number

Question

I have the following data

IDX	DATA
1	a
2	a
3	a
4	b
5	b
6	b
7	b
8	b
9	c
10	c

How can I, using Sqlite3, get the row count as such

IDX	DATA	COUNT
1	a	1 / 3
2	a	2 / 3
3	a	3 / 3
4	b	1 / 5
5	b	2 / 5
6	b	3 / 5
7	b	4 / 5
8	b	5 / 5
9	c	1 / 2
10	c	2 / 2

Thanks for you help

Answer 1

Use ROW_NUMBER:

SELECT
    IDX,
    DATA,
    ROW_NUMBER() OVER (PARTITION BY DATA ORDER BY IDX) COUNT
FROM yourTable
ORDER BY
    IDX;

Demo

Answer 2

You need ROW_NUMBER() window function:

SELECT *, 
       ROW_NUMBER() OVER (PARTITION BY DATA ORDER BY IDX) AS COUNT
FROM tablename