Cartesian multiplication in SQL and update null columns-CodePudding

I have these two tables in MySQL database:

tbl_hashs >

h_id	r_id	hash
1	122	xx
2	123	xx

tbl_sandbox >

h_id	r_id	hash
NULL	NULL	xx

finally I want to have this table:

query result should be like >>>

I think something like "Cartesian multiplication" can help me. but I can't do it in MySQL. please somebody help me with proper query.

CodePudding user response：

SELECT
   t1.h_id,
   t2.r_id,
   t2.hash
FROM tbl_hashs t1
CROSS JOIN tbl_hashs t2
ORDER BY t1.h_id

But I did not use tbl_sandbox, is that good ?