Script that works in MS SQL but not in POSTGRES, demonstrating different behavior of "select *" within an EXISTS clause.

ExistsSelectStarFromGrouped_MSSql-vs-Postgres.sql

-- The following code works in MS SQL 2019
-- But fails in Postgres 14.12 (PG 14 was released in 2021)

DROP TABLE IF EXISTS EMPLOYEE;

-- create
CREATE TABLE EMPLOYEE (
  empId INTEGER PRIMARY KEY,
  name VARCHAR(50) NOT NULL,
  dept VARCHAR(50) NOT NULL
);

-- insert
INSERT INTO EMPLOYEE VALUES (0001, 'Clark', 'Sales');
INSERT INTO EMPLOYEE VALUES (0002, 'Dave', 'Accounting');
INSERT INTO EMPLOYEE VALUES (0003, 'Ava', 'Sales');

-- fetch 
SELECT CASE 
  WHEN EXISTS (
    SELECT * FROM EMPLOYEE GROUP BY dept HAVING Count(*) > 1
  ) THEN 'there exists a dept with multiple employees'
  ELSE 'there are no depts with multiple employees'
END AS Result;