How to unfold the results of an Oracle query based on the value of a column

Question

I have a table on a Oracle DB with two columns. I would like to see every row repeated as many times as the number stored in the second column. The table looks like this:

Answer 1

with src (col1, col2) as (
    SELECT 'a', 2 FROM DUAL UNION ALL
    SELECT 'b', 3 FROM DUAL UNION ALL
    SELECT 'c', 1 FROM DUAL
)
SELECT
    src.*
FROM
    src
    JOIN (
        SELECT LEVEL val FROM DUAL
        CONNECT BY LEVEL <= (SELECT MAX(col2) FROM src)
    ) gen ON gen.val <= src.COL2
ORDER BY
    src.col1

or in Oracle 12 is possible to use

with src (col1, col2) as (
    SELECT 'a', 2 FROM DUAL UNION ALL
    SELECT 'b', 3 FROM DUAL UNION ALL
    SELECT 'c', 1 FROM DUAL
)
SELECT
    src.*
FROM
    src
    CROSS APPLY (SELECT NULL FROM DUAL CONNECT BY LEVEL <= src.col2)
ORDER BY
    col1;