Use Lowercase Identifiers for Compatibility

PostgreSQL folds unquoted identifiers to lowercase. Quoted mixed-case identifiers require quotes forever and cause issues with tools, ORMs, and AI assistants that may not recognize them.

Incorrect (mixed-case identifiers):

-- Quoted identifiers preserve case but require quotes everywhere
CREATE TABLE "Users" (
  "userId" bigint PRIMARY KEY,
  "firstName" text,
  "lastName" text
);

-- Must always quote or queries fail
SELECT "firstName" FROM "Users" WHERE "userId" = 1;

-- This fails - Users becomes users without quotes
SELECT firstName FROM Users;
-- ERROR: relation "users" does not exist

Correct (lowercase snake_case):

-- Unquoted lowercase identifiers are portable and tool-friendly
CREATE TABLE users (
  user_id bigint PRIMARY KEY,
  first_name text,
  last_name text
);

-- Works without quotes, recognized by all tools
SELECT first_name FROM users WHERE user_id = 1;

Common sources of mixed-case identifiers:

-- ORMs often generate quoted camelCase - configure them to use snake_case
-- Migrations from other databases may preserve original casing
-- Some GUI tools quote identifiers by default - disable this

-- If stuck with mixed-case, create views as a compatibility layer
CREATE VIEW users AS SELECT "userId" AS user_id, "firstName" AS first_name FROM "Users";

Reference: Identifiers and Key Words