Ver originalSELECT u.id, IFNULL(sbc.numAlertas,0) AS nAlertasFROM usuarios AS u LEFT JOIN (SELECT alertas.usuario, Count(*) AS numAlertas FROM alertas GROUP BY alertas.usuario) AS sbc ON u.id = sbc.usuario;
Ver originalSELECT usuarios.id, count(alertas.id)FROM usuarios LEFT OUTER JOIN alertasON usuarios.id = alertas.usuarioGROUP BY usuarios.id;