mysql实现组合情况

第一种组合情况(非排序非放回<)回组合 select `a`.`id` AS `id`,`b`.`id` AS `a` from (`test` `a` join `test` `b` on((`a`.`id` < `b`.`id`))) group by `a`.`id`,`b`.`id` order by `a`.`id` 第二种组合情况(非排序放回<=) select `a`.`id` AS `id`,`b`.`id` AS `a` from (`test` `a` join `test` `b` on((`a`.`id` <= `b`.`id`))) group by `a`.`id`,`b`.`id` order by `a`.`id` 第三种组合情况(排序非放回<>)
select `a`.`id` AS `id`,`b`.`id` AS `a` from
(`test` `a

mysql实现组合情况最先出现在Python成神之路。