Don't Use the String Concatenation Trick in SQL Predicates

CORRECT_StringConcat_predicate_Trick.sql

-- NOTA: no recuerdo por qué todo esto en lugar de un simple join ?!?!?!

-- DO NOT DO THIS!!!
CREATE INDEX idx_customer_name ON customer (last_name, first_name);

SELECT *
FROM customer
WHERE first_name || last_name IN (
  SELECT first_name || last_name
  FROM actor
)
/*
Is slow and can bring false matches:
-- What we expected
first_name || last_name = 'JENNIFER' || 'DAVIS'
-- What we got
first_name || last_name = 'JENNI' || 'FERDAVIS'
*/

-- Using an "impossible" separator is very slow (final hash join with full actor index):
CREATE INDEX idx_actor_name ON actor (last_name, first_name);

SELECT *
FROM customer
WHERE address_id = 10
AND first_name || '������' || last_name IN (
  SELECT first_name || '������' || last_name
  FROM actor
)
-- END of DO NOT DO THIS


-- ==========> DO THIS <===========
-- with ORACLE, PostgreSQL, ... "row constructors":
SELECT *
FROM customer
WHERE address_id = 10
AND (first_name, last_name) IN (
  SELECT first_name, last_name
  FROM actor
);

-- or with exists
SELECT *
FROM customer c
WHERE address_id = 10
AND EXISTS (
  SELECT 1
  FROM actor a
  WHERE c.first_name = a.first_name
  AND c.last_name = a.last_name
);