Postgres列或表名什么时候需要引号，什么时候不需要？

-- 不需要引号的情况
CREATE TABLE users (
    id SERIAL PRIMARY KEY,
    name VARCHAR(100),
    email VARCHAR(100)
);

-- 需要引号的情况
CREATE TABLE "user profile" (
    id SERIAL PRIMARY KEY,
    "full name" VARCHAR(100),
    email VARCHAR(100)
);

CREATE TABLE "user" (
    id SERIAL PRIMARY KEY,
    "select" VARCHAR(100),
    email VARCHAR(100)
);

CREATE TABLE "UserName" (
    id SERIAL PRIMARY KEY,
    "FirstName" VARCHAR(100),
    "LastName" VARCHAR(100)
);