Auto insert rows with repeated data, following two patterns - mysql

Question

I have a table that looks like this:
| id | letter | number |
|-----|--------|--------|
| 1 | a | 1 |
| 2 | b | 1 |
| 3 | c | 1 |
| 4 | d | 1 |
| 5 | a | 2 |
| 6 | b | 2 |
| 7 | c | 2 |
| 8 | d | 2 |
| 9 | a | 3 |
| 10 | b | 3 |
| 11 | c | 3 |
| 12 | d | 3 |
|etc..| | |
I'm trying to make an SQL statement that auto-fills the table following this pattern up to id 456.
So the letters are ABCD ABCD until the sequence ends, and each 'group' of 4 has a number, that should reach 114.
I'm not sure what the best way to tackle this is, any suggestions would be appreciated.

Answer 1

You can use the following sql script to insert the values required into your table:
INSERT INTO target (id, letter, `number`)
SELECT rn, col, (rn - 1) % 4 + 1 AS seq
FROM (
SELECT col, #rn := #rn + 1 AS rn
FROM (
SELECT 'a' AS col UNION ALL SELECT 'b' UNION ALL
SELECT 'c' UNION ALL SELECT 'd') AS t
CROSS JOIN (
SELECT 1 AS x UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 ) AS t1
CROSS JOIN (
SELECT 1 AS x UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 ) AS t2
CROSS JOIN (SELECT #rn := 0) AS var ) AS s
WHERE rn <= 456
The above query creates a numbers table of 121 rows using a 11 x 11 cartesian product. These rows are cross joined with in-line table ('a'), ('b'), ('c'), ('d') to produce a total of 484 rows. The outer query selects just the rows needed, i.e. 456 rows in total.
Note: If you want to insert values:
id, letter, number
1 'a' 1
2 'b' 1
3 'c' 1
4 'd' 1
5 'a' 2
6 'b' 2
7 'c' 2
8 'd' 2
... etc
instead of values:
id, letter, number
1 'a' 1
2 'b' 2
3 'c' 3
4 'd' 4
5 'a' 1
6 'b' 2
7 'c' 3
8 'd' 4
... etc
then simply replace (rn - 1) % 4 + 1 AS seq with (rn - 1) DIV 4 + 1 AS seq.
Demo here

Answer 2

It would help if you had a numbers table of some sort. Here is one method using cross join and some arithmetic:
select (#rn := #rn + 1) as id, l.letter, (n1 + n2*5 + n3*25) as number
from (select 0 as n union all select 1 as n union all select 2 as n union all select 3 union all select 4
) n1 cross join
(select 0 as n union all select 1 as n union all select 2 as n union all select 3 union all select 4
) n2 cross join
(select 0 as n union all select 1 as n union all select 2 as n union all select 3 union all select 4
) n3 cross join
(select 'a' as letter union all select 'b' union all select 'c' union all select 'd'
) l cross join
(select #rn := 0) params
where n1 + n2*5 + n3*25 < 114;