How to join rows pairwise randomly?

I have one table with player ids and names. For each round the table will be scrambled, split in half, and put side by side. Handling of unequal amount of rows in each group is not the scope of this question. The only thing I need to achieve is (upper half + lower half) OR (table a + table b) side by side. In detail table a as is + both columns from b without any reference to each other - row by row. i prepared some simple fiddle: https://dbfiddle.uk/vkahsaFj https://dbfiddle.uk/ASM405Co Some references: https://stackoverflow.com/questions/7983369/how-do-i-combine-a-mysql-query-and-subquery-when-theres-multiple-rows The result must be this: I tried all type of joins, temporary tables, grouping and so on. without success.