Is there any difference between such SQL queries?

Question

SQL

Request 1
SELECT COUNT(*) FROM TABLE1
Request 2

SELECT COUNT(*) FROM TABLE1 T1
LEFT OUTER JOIN TABLE2 T2
   ON T1.T2_ID = T2.ID
...
LEFT OUTER JOIN TABLEN TN
   ON T1.TN_ID = TN.ID

Those. Do JOINs affect the speed of query execution when counting the number of elements in a selection if they do not participate in conditions?

Answer 1

EXPLAIN to help you

Answer 2

* (asterisk) implies that you select everything.
So, first, a selection of N tables, and then only the calculation of the results
. Otherwise, what should he count?

Answer 3

Of course they do. In the first case, you make a selection from one table, in the second case, you link several tables, and in this case the DBMS has to look for the same IDs.