Encontrar valores de columna duplicados en la tabla con SQL
SELECT username, email, COUNT(*)
FROM users
GROUP BY username, email
HAVING COUNT(*) > 1
Cucumberman
SELECT username, email, COUNT(*)
FROM users
GROUP BY username, email
HAVING COUNT(*) > 1
SELECT *
FROM TableA A
WHERE NOT EXISTS (SELECT *
FROM TableB B
WHERE A.NUM = B.NUM);Multiple field=
SELECT username, email, COUNT(*)
FROM users
GROUP BY username, email
HAVING COUNT(*) > 1
Single field=
SELECT _column, COUNT(*)
FROM _table
GROUP BY _column
HAVING COUNT(*) > 1