When Oracle order by is sorted, null values are ranked first (nulls first)

in conclusion

• Use keywords nulls first/lastto treatment.
  • nulls first： The record representing the null value will be ranked first (whether it is asc or desc)
  • nulls last： The record representing the null value will be ranked last (whether it is asc or desc)

SELECT t.* FROM scott.emp t ORDER BY t.comm NULLS FIRST; -- null 值在最前面
SELECT t.* FROM scott.emp t ORDER BY t.comm NULLS LAST; -- null 值在最后面

Please note

Default:, null 默认为最大值 namely:

• Asc (ascending order), it is ranked last
• In desc (descending order), rank first