PostgreSQL中的collations用法详解

$ env | grep LC
$ env | grep LANG
LANG=en_US.UTF-8

postgres=# \l
                 List of databases
  Name  | Owner  | Encoding |  Collate  |  Ctype  |  Access privileges 
-----------+----------+----------+-------------+-------------+-----------------------
 postgres | postgres | UTF8   | en_US.UTF-8 | en_US.UTF-8 |
 template0 | postgres | UTF8   | en_US.UTF-8 | en_US.UTF-8 | =c/postgres     +
      |     |     |       |       | postgres=CTc/postgres
 template1 | postgres | UTF8   | en_US.UTF-8 | en_US.UTF-8 | =c/postgres     +
      |     |     |       |       | postgres=CTc/postgres
(4 rows)
 
postgres=#

postgres=# create database abce with LC_COLLATE = "en_US.UTF-8";
CREATE DATABASE
postgres=# create database abce2 with LC_COLLATE = "de_DE.UTF-8";
ERROR: new collation (de_DE.UTF-8) is incompatible with the collation of the template database (en_US.UTF-8)
HINT: Use the same collation as in the template database, or use template0 as template.
postgres=#

$ localectl list-locales

postgres=# select * from pg_collation ;

create table sale_fruit_count (
 id INTEGER primary key,
 name VARCHAR(50),
 code VARCHAR(10),
 area VARCHAR(50),
    area_code VARCHAR(10),
 sale_num INTEGER,
 price INTEGER
)

select * from sale_fruit_count order by area_code, sale_num desc

select * 
 from sale_fruit_count
 order by case area_code
     when 'HN' then 1
     when 'SX' then 2
  when 'SC' then 3
  when 'YN' then 4
  when 'XJ' then 5
  end asc
 , sale_num desc