How to fix ERROR: column "column_name" does not exist in PostgreSQL

# In psql terminal
\d your_table_name

-- List all columns in a table
SELECT column_name, data_type
FROM information_schema.columns
WHERE table_name = 'your_table_name'
ORDER BY ordinal_position;

-- Check if a specific column exists
SELECT column_name
FROM information_schema.columns
WHERE table_name = 'your_table_name'
AND column_name = 'column_name';

SELECT EmployeeID, firstName FROM employees;
-- ERROR: column "employeeid" does not exist
-- ERROR: column "firstname" does not exist

SELECT "EmployeeID", "firstName" FROM employees;

-- When creating tables, use lowercase names
CREATE TABLE employees (
  id serial PRIMARY KEY,
  employee_id varchar NOT NULL,
  first_name varchar,
  last_name varchar
);

-- Then reference without quotes
SELECT employee_id, first_name FROM employees;

-- WRONG - typo: "employe_name" instead of "employee_name"
SELECT employe_name FROM employees;
-- ERROR: column "employe_name" does not exist

-- CORRECT
SELECT employee_name FROM employees;

SELECT id, name, salary
FROM employees
JOIN departments ON employee_id = department_id;
-- ERROR: column "id" does not exist (which table?)

SELECT e.id, e.name, e.salary, d.name as dept_name
FROM employees e
JOIN departments d ON e.id = d.employee_id;

SELECT salary * 1.1 AS adjusted_salary
FROM employees
WHERE adjusted_salary > 50000;
-- ERROR: column "adjusted_salary" does not exist

SELECT salary * 1.1 AS adjusted_salary
FROM employees
WHERE salary > (50000 / 1.1)
ORDER BY adjusted_salary DESC;

SELECT adjusted_salary
FROM (
  SELECT salary * 1.1 AS adjusted_salary
  FROM employees
) subq
WHERE adjusted_salary > 50000;

-- Check which schema your table is in
SELECT table_schema, table_name
FROM information_schema.tables
WHERE table_name = 'employees';

-- Explicitly specify schema
SELECT id, name FROM public.employees;
SELECT id, name FROM hr.employees;

-- List all schemas and their tables
SELECT table_schema, COUNT(*) as table_count
FROM information_schema.tables
GROUP BY table_schema
ORDER BY table_schema;

SELECT first-name, email address FROM users;
-- ERROR: column "first" does not exist

SELECT "first-name", "email address" FROM users;

-- Use underscores instead of spaces or hyphens
CREATE TABLE users (
  id serial PRIMARY KEY,
  first_name varchar,
  email_address varchar
);

SELECT first_name, email_address FROM users;

# Search for old column reference in your code
grep -r "old_column_name" .

# Update all references to new column name
find . -type f -name "*.ts" -o -name "*.js" -o -name "*.sql" | \
xargs sed -i 's/old_column_name/new_column_name/g'