Sélections imbriquées / SELECT ... IN (SELECT...) / SELECT ... NOT IN (SELECT...)
Example 1
SELECT name FROM cia WHERE population > (SELECT population FROM cia WHERE name='United States')
Example 2
SELECT name FROM cia WHERE region = (SELECT region FROM cia WHERE name = 'Brazil')
"SELECT t1.cod_uni, t1.TEL_IMP_UNI, t1.comm, t1.dateu FROM testunite t1 WHERE t1.cod_uni NOT IN (SELECT t2.cod_uni FROM testunite2 t2) ORDER BY t1cod_uni";