nulls first 或 nulls last

本文主要是介绍nulls first 或 nulls last，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

#原数据
select * from jinbo.tel_info;person |    day     | recevice | miss 
--------+------------+----------+------A      | 2018-01-18 |       10 |    0B      | 2018-01-18 |        0 |    5C      | 2018-01-18 |        4 |    4D      | 2018-01-18 |        0 |    0E      | 2018-08-27 |        2 |     
(5 rows)# asc 的时候默认把null 后排， 相当于 order by miss asc nulls last 
select * from jinbo.tel_info order by miss asc;person |    day     | recevice | miss 
--------+------------+----------+------A      | 2018-01-18 |       10 |    0D      | 2018-01-18 |        0 |    0C      | 2018-01-18 |        4 |    4B      | 2018-01-18 |        0 |    5E      | 2018-08-27 |        2 |     
(5 rows)# asc nulls first
select * from jinbo.tel_info order by miss asc nulls first;person |    day     | recevice | miss 
--------+------------+----------+------E      | 2018-08-27 |        2 |     A      | 2018-01-18 |       10 |    0D      | 2018-01-18 |        0 |    0C      | 2018-01-18 |        4 |    4B      | 2018-01-18 |        0 |    5
(5 rows)#asc 的时候默认把null 前排， 相当于 order by miss asc nulls first 
select * from jinbo.tel_info order by miss desc;person |    day     | recevice | miss 
--------+------------+----------+------E      | 2018-08-27 |        2 |     B      | 2018-01-18 |        0 |    5C      | 2018-01-18 |        4 |    4A      | 2018-01-18 |       10 |    0D      | 2018-01-18 |        0 |    0#desc nulls last
select * from jinbo.tel_info order by miss desc nulls last;person |    day     | recevice | miss 
--------+------------+----------+------B      | 2018-01-18 |        0 |    5C      | 2018-01-18 |        4 |    4A      | 2018-01-18 |       10 |    0D      | 2018-01-18 |        0 |    0E      | 2018-08-27 |        2 |     
(5 rows)

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