can I SELECT query from two different tables at the same time.

Answer 1

yes

Ex:

SELECT * FROM table1 INNER JOIN table2 ON table1.id = table2.id;

Answer 2

Yep.
SELECT Client.ID, transacrions.number FROM Client, transacrions
LIMIT150
or else
SELECT c.ID, tr.number
FROM Client c
JOIN transacrions tr ON tr.client_ID = c.ID
LIMIT 150