What is the purpose of the keyword "ID" in PostgreSQL?
In PostgreSQL, inserting a column named

"ID"


is one thing. Inserting a column named 

ID


is another.

create table test (
  "ID" integer not null
);

insert into test values (1);

select *
from test
where ID = 1;

ERROR: column "id" does not exist



  Quoting an identifier also makes it case-sensitive, whereas unquoted
  names are always folded to lower case.