For example, the table content is
id name
1 a
2 b
3 c
4 d
th The first download id is 1
The first download id is 2
The first download id is 3
The first download id is 4
## After #id is 4, it starts from 1 again and keeps looping indefinitely. It must be able to support high concurrency! Before I used to save the id in another table, every time
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First sort in forward order and download one round, until the last id, then reverse sort and download one round, until the last id, and then in forward order, and continue indefinitely
The first download id is 1
The second download id is 2
The third download id is 3
The fourth download id is 4