Código SQL:
Ver originalSELECT CASE WHEN total>=1 THEN 'True' ELSE 'False' FROM(
SELECT COUNT(*) AS total FROM tblSubUsuario AS t1
LEFT JOIN tblUsuario AS t2 ON (t1.FkIdUsuario =t2.idusuario)
WHERE t2.usuario='valor1' AND t1.subusuario='valor2'
) AS tabla
saludos!!!