Data cleaning

CHECK (emp_name = upper(emp_name))

CREATE OR REPLACE FUNCTION uppercase_name () 
  RETURNS trigger AS $$
    BEGIN
        NEW.emp_name = upper(NEW.emp_name);
        RETURN NEW;
    END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER uppercase_emp_name
BEFORE INSERT OR UPDATE OR DELETE ON salaries
    FOR EACH ROW EXECUTE PROCEDURE uppercase_name ();

postgres=# SELECT set_salary('arnold',80);
-[ RECORD 1 ]-------------------
set_salary | INSERTED USER arnold

postgres=# SELECT * FROM salaries;
-[ RECORD 1 ]---
emp_name | Bob
salary   | 1300
-[ RECORD 2 ]---
emp_name | Fred
salary   | 750
-[ RECORD 3 ]---
emp_name | Frank
salary   | 100
-[ RECORD 4 ]---
emp_name |  ARNOLD
salary   | 80

postgres=# update salaries set emp_name = upper(emp_name) where not emp_name = upper(emp_name);
UPDATE 3                                                        
postgres=# alter table salaries add constraint emp_name_must_be_uppercasepostgres CHECK (emp_name = upper(emp_name));
ALTER TABLE