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

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)

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 "public.exchange"
 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      | {}