Postgresql query automatically converts uppercase names to lowercase cases

I won't say much nonsense, let's just read the code~

 SELECT sum(aa) as "recordNumber" FROM table
 SELECT sum(aa) as recordNumber FROM table

The postgis query field converts the field field to lowercase. If uppercase characters are required, double quotes are required.

Supplement: Table name, column name, user name case issues in Postgresql

Note: It is double quotes, single quotes may be parsed into ordinary characters, so it is an unrecognized field.

highgo=# create table "ExChange" (id int);
CREATE TABLE
highgo=# create table ExChange (id int);
CREATE TABLE
highgo=# \d
  List of relations
 Schema | Name | Type | Owner
----------------+----------+-------+--------
 oracle_catalog | dual | view | highgo
 public  | ExChange | table | highgo
 public  | exchange | table | highgo
 public  | myt | table | highgo
 public  | t1 | table | highgo
 public  | tran | table | highgo
(6 rows) 
 
highgo=# insert into exchange values (1);
INSERT 0 1
highgo=# insert into "ExChange" values (2);
INSERT 0 1
 
highgo=# select * FROM exchange ;
 id
----
 1
(1 row)
highgo=# select * FROM ExChange ;
 id
----
 1
(1 row)
 
highgo=# select * FROM "ExChange" ;
 id
----
 2
(1 row) 
 
highgo=# insert into ExChange values (2);
INSERT 0 1
highgo=# select * FROM "ExChange" ;
 id
----
 2
(1 row)
 
highgo=# select * FROM exchange ;
 id
----
 1
 2
(2 rows)

> As can be seen from the above, if double quotes are not added, the table names will be converted to lowercase. If you want to mix upper and lower case, you need to add double quotes.

highgo=# create table exchange (ID int,id int);
ERROR: 42701: column "id" specified more than once
highgo=# create table exchange (ID int,name text);
CREATE TABLE
highgo=# select id from exchange ;
 id
----
(0 rows)
 
highgo=# select ID from exchange ;
 id
----
(0 rows)
 
highgo=# select "ID" from exchange ;
ERROR: 42703: column "ID" does not exist
LINE 1: select "ID" from exchange ;
 
highgo=# \d exchange
 Table ""
 Column | Type | Modifiers
--------+---------+-----------
 id | integer |
 name | text |
 
highgo=# \du
     List of roles
 Role name |    Attributes    | Member of
-----------+------------------------------------------------------------+-----------
 aaa |        | {}
 gpadmin | Superuser, Create role, Create DB    | {}
 highgo | Superuser, Create role, Create DB, Replication, Bypass RLS | {}
 replica | Replication      | {}
 
highgo=# create table AAA;
ERROR: 42601: syntax error at or near ";"
LINE 1: create table AAA;
   ^
highgo=# create user AAA;
ERROR: 42710: role "aaa" already exists
highgo=# create user "AAA";
CREATE ROLE
highgo=# \du
     List of roles
 Role name |    Attributes    | Member of
-----------+------------------------------------------------------------+-----------
 AAA |        | {}
 aaa |        | {}
 gpadmin | Superuser, Create role, Create DB    | {}
 highgo | Superuser, Create role, Create DB, Replication, Bypass RLS | {}
 replica | Replication      | {}

Experiments have shown that fields will be automatically converted to lowercase like users, unless double quotes are added. In fact, the best way is to use lowercase all, so as to minimize the occurrence of problems.

The above is personal experience. I hope you can give you a reference and I hope you can support me more. If there are any mistakes or no complete considerations, I would like to give you advice.